Dr Inyoung Kim

Dr Inyoung Kim

ARC Decra Fellow

School of Engineering

Career Summary

Biography

Dr. Kim obtained her PhD degree under supervision of Prof. Seong-Ju Hwang at Ewha Womans University, Republic of Korea in 2014. Her PhD work primarily involved on the syntheses of two dimensional (2D) inorganic nanohybrids for photocatalytic and energy storage applications. As her PhD research required the extensive analysis of local structure of the prepared nanosheet materials, she was given the access constantly to the X-ray absorption spectroscopy (XAS) beamline at the Pohang Accelerator Laboratory annually. As a result of this outstanding work, she was awarded with Excellent Researcher Prize by Korean Synchrotron Radiation User’s Association in 2012. She also received an esteemed Prize for Excellent PhD Thesis awarded by The Korean Chemical Society.

After completing her PhD in 2014, she was offered a postdoctoral fellow position from Ewha Womans University. In addition to her research activity, she had taught the courses on Inorganic Chemistry for graduate students in semester 1, 2015 at Dongguk University, Republic of Korea. In 2016, She joined Prof. Ajayan Vinu’s group housed at the Future Industries Institute, the University of South Australia. In 2017, she was awarded Australian Research Council (ARC) Discovery Early Career Researcher Award (DECRA) which is one of the highly competitive and honourable fellowship in Australia. In Dec. 2017, she was offered a senior lecturer position by the Global Innovative Center for Advanced Nanomaterials and Faculty of Engineering and Built Environment at The University of Newcastle.

Dr. Kim has been working in the past 11 years on the design and characterisation of organic/inorganic nanohybrid materials composed of 2D inorganic nanosheets (transition metal oxides, layered double hydroxides and transition metal chalcogenides), nanocompounds (nanowires and nanoparticles), highly ordered nanoporous materials (silicas, MOF and carbon nitrides), biomolecules and conducting polymers. She aims to apply the nanohybrid materials in the fields of energy storage and conversion (secondary and micro batteries, and nanogenerators), photoelectrochemical conversion (water splitting and CO2 reduction), CO2 capture and conversion, adsorption and separation (toxic compounds and fine chemicals). One of her research interest is the examination of atomic structure of nanomaterials using XAS. Since 2008, she has published more than 75 refereed international journal articles with an H-index of 25.


Qualifications

  • Doctor of Philosophy (Materials Chemistry), EWHA Womans University, Korea

Keywords

  • Energy
  • Environment
  • Hybrid materials
  • Inorganic chemistry
  • Materials science
  • Nanosheets
  • Nanotechnology
  • Porouse materials
  • Solid state chemistry

Languages

  • Korean (Mother)
  • English (Fluent)

Fields of Research

Code Description Percentage
030606 Structural Chemistry and Spectroscopy 20
091305 Energy Generation, Conversion and Storage Engineering 50
030302 Nanochemistry and Supramolecular Chemistry 30

Professional Experience

Academic appointment

Dates Title Organisation / Department
1/12/2017 -  ARC DECRA Fellow The University of Newcastle - Research and Innovation Division
Global Innovative Center for Advanced Nanomaterials
Australia
15/04/2016 - 30/11/2017 Research Associate The University of South Australia
Future Industries Institute
Australia
2/03/2015 - 19/06/2015 Lecturer Dongguk University
Chemistry
Korea, Republic of
1/03/2014 - 31/03/2016 Postdoctoral Fellow Ewha Womans University
Chemistry and Nanoscience
Korea, Republic of

Awards

Award

Year Award
2017 Discovery Early Career Researcher Award
ARC (Australian Research Council)

Prize

Year Award
2013 A Prize for Excellent Presentation
Korean Chemical Society
2012 A Prize for Excellent Presentation
Korean Chemical Society
2012 A Prize for Excellent Oral Presentation
Ewha Basic Science Research Institution
2011 A Prize for Excellent Presentation
Korean Society of Photoscience
2011 A Prize for Excellent Oral Presentation
Korean Electrochemical Society
2009 A Prize for Excellent Presentation
2009 International Conference on Nano Science and Nano Technology
2008 A Prize for Excellent Presentation
Nano Korea
2008 A Prize for Excellent Presentation
3rd Asian Conference on Electrochemical Power Sources

Research Award

Year Award
2014 A Prize for Excellent PhD Thesis
Ewha Womans University
2014 A Prize for Excellent PhD Thesis
Korean Chemical Society
2012 A Prize for Excellent Research
Korean Synchrotron User's Association

Scholarship

Year Award
2010 Hi-Seoul Scholarship for Graduate Student
Seoul Government

Invitations

Speaker

Year Title / Rationale
2019 Novel two dimensional nanohybrid materials for energy generation and storage applications
2019 Highly ordered mesoporous materials for electrocatalysis and secondary batteries
2018 Effect of tailored core structure of carbon nitride on its oxygen reduction activity
2017 Reassembly of colloidal nanosheets for 2D hybrid materials applicable for energy and environmental technologies
2016 Progress in inorganic nanosheet-based hybrids for energy and environmental Technologies
2016 Inorganic nanosheet-based hybrids for energy and environmental technologies
2015 Recent progress in the exfoliation of layered materials
2015 2D Nanosheet-based hybrid photocatalysts
2014 2D Nanosheet-based hybrids for energy and environment
2014 2D Nanostructured Hybrid Membrane of Graphene-Layered Titanate with High Antibacterial Activity
2014 Strongly-coupled 2D nanohybrids of titanate-graphene with novel physicochemical properties for photocatalyst and antibacterial matrix
2012 Soft-chemical synthesis of mixed colloidal suspension and hybrid paper of layered titanate and graphene nanosheets

Grant Reviews

Year Grant Amount
2019 Discovery Project
C1200 - Aust Competitive - ARC - 1200, C1200 - Aust Competitive - ARC - 1200
$465,863
2019 Discovery Early Career Researcher Award
C1200 - Aust Competitive - ARC - 1200, C1200 - Aust Competitive - ARC - 1200
$374,916
2019 Discovery Early Career Researcher Award
C1200 - Aust Competitive - ARC - 1200, C1200 - Aust Competitive - ARC - 1200
$410,316
2019 Australian Synchrotron Beamline Proposal
C1700 - Aust Competitive - Other - 1700, C1700 - Aust Competitive - Other - 1700
$1,270
2019 Australian Synchrotron Beamline Proposal
C1700 - Aust Competitive - Other - 1700, C1700 - Aust Competitive - Other - 1700
$1,270
2018 Discovery Project
C1200 - Aust Competitive - ARC - 1200, C1200 - Aust Competitive - ARC - 1200
$548,497
2018 Discovery Project
C1200 - Aust Competitive - ARC - 1200, C1200 - Aust Competitive - ARC - 1200
$686,519
2017 Discovery Project
C1200 - Aust Competitive - ARC - 1200, C1200 - Aust Competitive - ARC - 1200
$750,143
2017 Discovery Project
C1200 - Aust Competitive - ARC - 1200, C1200 - Aust Competitive - ARC - 1200
$589,619

Teaching

Code Course Role Duration
CHE6004-01 Advanced Inorganic Chemistry
Dongguk University
Lecturer 2/03/2015 - 30/06/2015
Edit

Publications

For publications that are currently unpublished or in-press, details are shown in italics.


Book (1 outputs)

Year Citation Altmetrics Link
2017 Nakato T, Kawamata J, Takagi S, Inorganic Nanosheets and Nanosheet-Based Materials Fundamentals and Applications of Two-Dimensional Systems, Springer, 542 (2017)

Journal article (82 outputs)

Year Citation Altmetrics Link
2019 Cha W, Kim IY, Lee JM, Kim S, Ramadass K, Gopalakrishnan K, et al., 'Sulfur-Doped Mesoporous Carbon Nitride with an Ordered Porous Structure for Sodium-Ion Batteries.', ACS Appl Mater Interfaces, 11 27192-27199 (2019) [C1]
DOI 10.1021/acsami.9b07657
Co-authors Ajayan Vinu, Kavitha Ramadass
2019 Singh G, Lakhi KS, Sil S, Bhosale SV, Kim IY, Albahily K, Vinu A, 'Biomass derived porous carbon for CO2 capture', Carbon, 148 164-186 (2019) [C1]
DOI 10.1016/j.carbon.2019.03.050
Citations Scopus - 10Web of Science - 3
Co-authors Ajayan Vinu
2019 Ilbeygi H, Kim IY, Kim MG, Cha W, Kumar PSM, Park D-H, Vinu A, 'Highly Crystalline Mesoporous Phosphotungstic Acid: A High-Performance Electrode Material for Energy-Storage Applications', ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 58 10849-10854 (2019) [C1]
DOI 10.1002/anie.201901224
Citations Scopus - 2Web of Science - 2
Co-authors Ajayan Vinu
2018 Yang J, Muckel F, Choi BK, Lorenz S, Kim IY, Ackermann J, et al., 'Co

© 2018 American Chemical Society. Magic-sized clusters represent materials with unique properties at the border between molecules and solids and provide important insights into th... [more]

© 2018 American Chemical Society. Magic-sized clusters represent materials with unique properties at the border between molecules and solids and provide important insights into the nanocrystal formation process. However, synthesis, doping, and especially structural characterization become more and more challenging with decreasing cluster size. Herein, we report the successful introduction of Co2+ ions into extremely small-sized CdSe clusters with the intention of using internal ligand field transitions to obtain structural insights. Despite the huge mismatch between the radii of Cd2+ and Co2+ ions (>21%), CdSe clusters can be effectively synthesized with a high Co2+ doping concentration of ~10%. Optical spectroscopy and mass spectrometry suggest that one or two Co2+ ions are substitutionally embedded into (CdSe)13 clusters, which is known as one of the smallest CdSe clusters. Using magnetic circular dichroism spectroscopy on the intrinsic ligand field transitions between the different 3d orbitals of the transition metal dopants, we demonstrate that the Co2+ dopants are embedded on pseudotetrahedral selenium coordinated sites despite the limited number of atoms in the clusters. A significant shortening of Co-Se bond lengths compared to bulk or nanocrystals is observed, which results in the metastability of Co2+ doping. Our results not only extend the doping chemistry of magic-sized semiconductor nanoclusters, but also suggest an effective method to characterize the local structure of these extremely small-sized clusters.

DOI 10.1021/acs.nanolett.8b03627
Citations Scopus - 1
2018 Jang JH, Lee E, Xiao P, Park K, Kim IY, Henkelman G, et al., 'Superior Oxygen Electrocatalysis on RuSe

© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim A one-step, facile supercritical-ethanol-fluid synthesis of Se-modified Ru nanoparticles nucleated on carbon defects is rep... [more]

© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim A one-step, facile supercritical-ethanol-fluid synthesis of Se-modified Ru nanoparticles nucleated on carbon defects is reported, and it is demonstrated that these nanoparticles provide, with >70% efficiency at 1 A g-1, a highly active and reversible oxygen-reduction/oxygen-evolution reaction on an air cathode in a nonaqueous electrolyte. The Se modification not only prevents Ru oxidation during charge/discharge cycling, but also improves the catalytic activity by promoting Li2O2 versus Li2O deposited on the Ru particles during discharge. A computational calculation with density functional theory supports the role of a larger electron transfer to the oxygen of Li2O2 adsorbed on a surface layer of RuSe2-d than on a surface layer of RuO2, thereby shifting the more stable adsorbent from Li2O to Li2O2.

DOI 10.1002/aenm.201702037
Citations Scopus - 3
2018 Adpakpang K, Oh SM, Agyeman DA, Jin X, Jarulertwathana N, Kim IY, et al., 'Holey 2D Nanosheets of Low-Valent Manganese Oxides with an Excellent Oxygen Catalytic Activity and a High Functionality as a Catalyst for Li O

© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Holey 2D nanosheets of low-valent Mn2O3 can be synthesized by thermally induced phase transition of exfoliated layered MnO2... [more]

© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Holey 2D nanosheets of low-valent Mn2O3 can be synthesized by thermally induced phase transition of exfoliated layered MnO2 nanosheets. The heat treatment of layered MnO2 nanosheets at elevated temperatures leads not only to transitions to low-valent manganese oxides but also to the creation of surface hole in the 2D nanosheet crystallites. Despite distinct phase transitions, highly anisotropic 2D morphology of the precursor MnO2 material remains intact upon the heat treatment whereas the diameter of surface hole becomes larger with increasing heating temperature. The obtained holey 2D Mn2O3 nanosheets show promising electrocatalyst performances for oxygen evolution reaction, which are much superior to that of nonporous Mn2O3 crystal. Among the present materials, the holey Mn2O3 nanosheet calcined at 500 °C displays the best electrocatalyst functionality with markedly decreased overpotential, indicating the importance of heating condition in optimizing the electrocatalytic activity. Of prime importance is that this material shows much better catalytic activity for Li¿O2 batteries than does nonporous Mn2O3, underscoring the critical role of porous 2D morphology in this functionality. This study clearly demonstrates the unique advantage of holey 2D nanosheet morphology in exploring economically feasible transition metal oxide-based electrocatalysts and electrodes for Li¿O2 batteries.

DOI 10.1002/adfm.201707106
Citations Scopus - 16
2018 Kwon NH, Kim M, Jin X, Lim J, Kim IY, Lee NS, et al., 'A rational method to kinetically control the rate-determining step to explore efficient electrocatalysts for the oxygen evolution reaction', NPG Asia Materials, 10 659-669 (2018)

© 2018, The Author(s). A novel, rational, and efficient way to explore high-performance electrocatalysts was developed by controlling the reaction kinetics of the rate-determining... [more]

© 2018, The Author(s). A novel, rational, and efficient way to explore high-performance electrocatalysts was developed by controlling the reaction kinetics of the rate-determining step (RDS). Density functional theory (DFT) calculations demonstrate that the RDS for the oxygen evolution reaction driven by transition metal hydroxides/oxides, i.e., surface adsorption of OH-/OOH¿ species, can be significantly promoted by increasing the electrophilicity of electrocatalysts via hybridization with electron-withdrawing inorganic nanosheets. As predicted by DFT calculation, the hybridization of Ni¿Fe-layered double hydroxide (LDH)/Ni¿Co-LDH, with RuO2 nanosheets (1.0 wt%) leads to significant lowering of the overpotentials to 207/276 mV at 10 mA cm-2, i.e., one of the smallest overpotentials for LDH-based materials, with the increase in the current density. The necessity of a very small amount of RuO2 nanosheets (1.0 wt%) to optimize the electrocatalyst activity highlights the remarkably high efficiency of the RuO2 addition. The present study underscores the importance of kinetic control of the RDS via hybridization with electron-withdrawing species for exploring novel efficient electrocatalysts.

DOI 10.1038/s41427-018-0060-3
Citations Scopus - 8
2018 Kim IY, Lee JM, Hwang EH, Pei YR, Jin WB, Choy JH, Hwang SJ, 'Correction: Water-floating nanohybrid films of layered titanate-graphene for sanitization of algae without secondary pollution (RSC Advances (2016) 6 (98528-98535) DOI: 10.1039/C6RA24140A)', RSC Advances, 8 18109 (2018)

© 2018 The Royal Society of Chemistry. In the published paper, the affiliations of Eui-Ho Hwang and Woo-Bin Jin were wrongly designated, and the corrected version is shown below. ... [more]

© 2018 The Royal Society of Chemistry. In the published paper, the affiliations of Eui-Ho Hwang and Woo-Bin Jin were wrongly designated, and the corrected version is shown below. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.

DOI 10.1039/c8ra90039f
2018 Adpakpang K, Oh SM, Agyeman DA, Jin X, Jarulertwathana N, Kim IY, et al., 'Oxygen Evolution Reaction: Holey 2D Nanosheets of Low-Valent Manganese Oxides with an Excellent Oxygen Catalytic Activity and a High Functionality as a Catalyst for Li-O2 Batteries (Adv. Funct. Mater. 17/2018)', Advanced Functional Materials, 28 1870114-1870114 (2018)
DOI 10.1002/adfm.201870114
2018 Kim IY, Kim S, Jin X, Premkumar S, Chandra G, Lee N-S, et al., 'Ordered Mesoporous C3N5 with a Combined Triazole and Triazine Framework and Its Graphene Hybrids for the Oxygen Reduction Reaction (ORR)', ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 57 17135-17140 (2018) [C1]
DOI 10.1002/anie.201811061
Citations Scopus - 9Web of Science - 9
Co-authors Ajayan Vinu
2017 Jo YK, Kim M, Jin X, Kim IY, Lim J, Lee NS, et al., 'Hybridization of a Metal-Organic Framework with a Two-Dimensional Metal Oxide Nanosheet: Optimization of Functionality and Stability', Chemistry of Materials, 29 1028-1035 (2017)

© 2016 American Chemical Society. An effective way to improve the functionalities and stabilities of metal-organic frameworks (MOFs) is developed by employing exfoliated metal oxi... [more]

© 2016 American Chemical Society. An effective way to improve the functionalities and stabilities of metal-organic frameworks (MOFs) is developed by employing exfoliated metal oxide 2D nanosheets as matrix for immobilization. Crystal growth of zeolitic imidazolate framework-8 (ZIF-8) nanocrystals on the surface of layered titanate nanosheets yields intimately coupled nanohybrids of ZIF-8-layered titanate. The resulting nanohybrids show much greater surface areas and larger pore volumes than do the pristine ZIF-8, leading to the remarkable improvement of the CO2 adsorption ability of MOF upon hybridization. Of prime importance is that the thermal- and hydrostabilities of ZIF-8 are significantly enhanced by a strong chemical interaction with the robust titanate nanosheet. A strong interfacial interaction between ZIF-8 and the layered titanate is verified by molecular mechanics simulations and spectroscopic analysis. The universal applicability of the present strategy for the coupling of MOFs and metal oxide nanosheets is substantiated by the stabilization of Ti-MOF-NH2 via the immobilization on exfoliated V2O5 nanosheets. The present study underscores that hybridization with metal oxide 2D nanosheets provides an efficient and universal synthetic route to novel MOF-based hybrid materials with enhanced gas adsorptivity and stability.

DOI 10.1021/acs.chemmater.6b03788
Citations Scopus - 12
2017 Oh SM, Kim IY, Patil SB, Park B, Lee JM, Adpakpang K, et al., 'Improvement of na ion electrode activity of metal oxide via composite formation with metal sulfide', ACS Applied Materials and Interfaces, 9 2249-2260 (2017)

© 2016 American Chemical Society. The composite formation with a conductive metal sulfide domain can provide an effective methodology to improve the Na-ion electrode functionality... [more]

© 2016 American Chemical Society. The composite formation with a conductive metal sulfide domain can provide an effective methodology to improve the Na-ion electrode functionality of metal oxide. The heat treatment of TiO2(B) under CS2 flow yields an intimately coupled TiO2(B)-TiS2 nanocomposite with intervened TiS2 domain, since the reaction between metal oxide and CS2 leads to the formation of metal sulfide and CO2. The negligible change in lattice parameters and significant enhancement of visible light absorption upon the reaction with CS2 underscore the formation of conductive metal sulfide domains. The resulting TiO2(B)-TiS2 nanocomposites deliver greater discharge capacities with better rate characteristics for electrochemical sodiation-desodiation process than does the pristine TiO2(B). The 23Na magic angle spinning nuclear magnetic resonance analysis clearly demonstrates that the electrode activities of the present nanocomposites rely on the capacitive storage of Na+ ions, and the TiS2 domains in TiO2(B)-TiS2 nanocomposites play a role as mediators for Na+ ions to and from TiO2(B) domains. According to the electrochemical impedance spectroscopy, the reaction with CS2 leads to the significant enhancement of charge transfer kinetics, which is responsible for the accompanying improvement in electrode performance. The present study provides clear evidence for the usefulness in composite formation between the semiconducting metal oxide and metal sulfide in exploring new efficient NIB electrode materials.

DOI 10.1021/acsami.6b11220
Citations Scopus - 3
2017 Jin X, Lim J, Ha Y, Kwon NH, Shin H, Kim IY, et al., 'A critical role of catalyst morphology in low-temperature synthesis of carbon nanotube-transition metal oxide nanocomposite', Nanoscale, 9 12416-12424 (2017)

© The Royal Society of Chemistry 2017. The effect of the catalyst morphology on the growth of carbon nanotubes (CNT) on nanostructured transition metal oxides was investigated to ... [more]

© The Royal Society of Chemistry 2017. The effect of the catalyst morphology on the growth of carbon nanotubes (CNT) on nanostructured transition metal oxides was investigated to study a novel low-temperature synthetic route to functional CNT-transition metal oxide nanocomposites. Among several nanostructured manganese oxides with various morphologies and structures, only exfoliated 2D nanosheets of layered MnO2 acted as an effective catalyst for the chemical vapor deposition of CNT at low temperatures of 400-500 °C, which emphasizes the critical role of the catalyst morphology in CNT growth. Heat treatment of the MnO2 nanosheets under a C2H2 flow induced the deposition of CNT, as well as a phase transition to a 2D ordered assembly of MnO nanoparticles. The resulting CNT-MnO nanocomposites displayed excellent functionalities in Li-ion electrodes with huge discharge capacities and good rate characteristics, which highlights the usefulness of the present method for studying functional CNT-metal oxide nanocomposites. Electron microscopy and density functional theory calculations propose a formation mechanism via the efficient adsorption of carbon on the MnO2 nanosheets followed by the surface diffusion of carbon. It is of prime importance that the substitution of Fe for layered MnO2 nanosheets remarkably improved the efficiency of the formation of CNT by enhancing the surface adsorption of carbon species. This is the first report of the efficient growth of CNT at a very low temperature of 400 °C. The universal merit of the 2D nanosheet morphology was confirmed by the successful synthesis of a CNT-TiO2 nanocomposite with exfoliated titanate nanosheets. The present study demonstrates that employing exfoliated transition metal oxide nanosheets as catalysts provides an efficient low-temperature synthetic route to functional CNT-transition metal oxide nanocomposites.

DOI 10.1039/c7nr03598e
Citations Scopus - 4
2017 Singh G, Lakhi KS, Kim IY, Kim S, Srivastava P, Naidu R, Vinu A, 'Highly Efficient Method for the Synthesis of Activated Mesoporous Biocarbons with Extremely High Surface Area for High-Pressure CO2 Adsorption.', ACS Applied Materials & Interfaces, 9 29782-29793 (2017) [C1]
DOI 10.1021/acsami.7b08797
Citations Scopus - 28Web of Science - 26
Co-authors Ajayan Vinu, Ravi Naidu
2017 Singh G, Kim IY, Lakhi KS, Srivastava P, Naidu R, Vinu A, 'Single step synthesis of activated bio-carbons with a high surface area and their excellent CO2 adsorption capacity', CARBON, 116 448-455 (2017) [C1]
DOI 10.1016/j.carbon.2017.02.015
Citations Scopus - 71Web of Science - 64
Co-authors Ravi Naidu, Ajayan Vinu
2017 Singh G, Kim IY, Lakhi KS, Joseph S, Srivastava P, Naidu R, Vinu A, 'Heteroatom functionalized activated porous biocarbons and their excellent performance for CO2 capture at high pressure', JOURNAL OF MATERIALS CHEMISTRY A, 5 21196-21204 (2017)
DOI 10.1039/c7ta07186h
Citations Scopus - 21Web of Science - 21
Co-authors Ajayan Vinu, Ravi Naidu, Stalin Joseph
2016 Gunjakar JL, Jo YK, Kim IY, Lee JM, Patil SB, Pyun JC, Hwang SJ, 'A chemical bath deposition route to facet-controlled Ag

© 2016 Published by Elsevier Inc. A facile, economic, and reproducible chemical bath deposition (CBD) method is developed for the fabrication of facet-controlled Ag3PO4 thin films... [more]

© 2016 Published by Elsevier Inc. A facile, economic, and reproducible chemical bath deposition (CBD) method is developed for the fabrication of facet-controlled Ag3PO4 thin films with enhanced visible light photocatalytic activity. The fine-control of bath temperature, precursor, complexing agent, substrate, and solution pH is fairly crucial in preparing the facet-selective thin film of Ag3PO4 nanocrystal. The change of precursor from silver nitrate to silver acetate makes possible the tailoring of the crystal shape of Ag3PO4 from cube to rhombic dodecahedron and also the bandgap tuning of the deposited films. The control of [Ag+]/[phosphate] ratio enables to maximize the loading amount of Ag3PO4 crystals per the unit area of the deposited film. All the fabricated Ag3PO4 thin films show high photocatalytic activity for visible light-induced degradation of organic molecules, which can be optimized by tailoring the crystal shape of the deposited crystals. This CBD method is also useful in preparing the facet-controlled hybrid film of Ag3PO4-ZnO photocatalyst. The present study clearly demonstrates the usefulness of the present CBD method for fabricating facet-controlled thin films of metal oxosalt and its nanohybrid.

DOI 10.1016/j.jssc.2016.05.028
Citations Scopus - 9
2016 Lee JM, Kwon NH, Kim IY, Hwang SJ, 'A vapor-phase carbon-deposition route to efficient inorganic nanosheet-based electrodes', Materials Letters, 179 217-221 (2016)

© 2016 Elsevier B.V. Efficient inorganic nanosheet-based electrode materials can be synthesized by the calcination of exfoliated Ti 5 NbO 14 nanosheets under C 2 H 2 flow. While ... [more]

© 2016 Elsevier B.V. Efficient inorganic nanosheet-based electrode materials can be synthesized by the calcination of exfoliated Ti 5 NbO 14 nanosheets under C 2 H 2 flow. While the calcination in Ar atmosphere causes a phase transformation from layered Ti 5 NbO 14 to TiO 2 and Nb 2 O 5 , employing C 2 H 2 atmosphere leads to the maintenance of the original layered structure of Ti 5 NbO 14 upon the heat-treatment, which is attributable to the stabilization of layered lattice by surface passivation by deposited carbon layer. The resulting carbon@titanoniobate materials show mesoporous house-of-cards-type stacking structure of 2D nanosheets. This carbon@titanoniobate material delivers large discharge capacity of ~320¿mA¿h¿g -1 with excellent cyclability and rate performance, which is much superior to that of carbon-free homologue. The present study clearly demonstrates that the heat-treatment under C 2 H 2 flow provides a simple and effective route to high-performance inorganic nanosheet-based electrode materials.

DOI 10.1016/j.matlet.2016.05.021
Citations Scopus - 1
2016 Lee S, Jin X, Kim IY, Gu TH, Choi JW, Nahm S, Hwang SJ, 'Superior Additive of Exfoliated RuO

© 2016 American Chemical Society. An effective way to optimize the electrode performance of metal oxide was developed by employing exfoliated 2D RuO2 nanosheet as a conducting add... [more]

© 2016 American Chemical Society. An effective way to optimize the electrode performance of metal oxide was developed by employing exfoliated 2D RuO2 nanosheet as a conducting additive. The exfoliated RuO2 nanosheet was easily incorporated into the Li-MnO2 nanocomposite via a simple mixing of exfoliated RuO2 and MnO2 nanosheets, followed by the restacking with Li+ ions. The incorporation of RuO2 nanosheet was found to be quite effective in increasing the surface area of the restacked Li-MnO2 nanocomposite. The obtained heterolayered Li-MnO2-RuO2 nanocomposites delivered much greater specific capacitances than do the pristine Li-MnO2 and Li-RuO2 nanocomposites. Considering the fact that the RuO2 nanosheet has higher electrode activity than the MnO2 nanosheet, the greater specific capacitance of Li-MnO2-RuO2 nanocomposite than that of Li-RuO2 strongly suggests that the incorporation of a small amount of RuO2 nanosheet into the restacked Li-MnO2 nanocomposite induces a synergistic improvement in its electrode activity. Of prime importance is that the Li-MnO2-RuO2 nanocomposites showed somewhat better electrode performances than the reduced graphene oxide (rG-O)-incorporated Li-MnO2-rG-O homologues, attributable to more efficient charge transport and pore structure upon RuO2 incorporation. The hydrophilic RuO2 nanosheet is more effective in making a stronger chemical interaction with hydrophilic MnO2 and also in depressing the self-aggregation of nanosheets compared to hydrophobic rG-O nanosheet. The present study clearly demonstrates that the RuO2 nanosheet can be used as a better additive for improving the electrode performance of metal oxides compared with widely used rG-O.

DOI 10.1021/acs.jpcc.6b02257
Citations Scopus - 20
2016 Mohd Sidek HB, Jo YK, Kim IY, Hwang SJ, 'Stabilization of Layered Double Oxide in Hybrid Matrix of Graphene and Layered Metal Oxide Nanosheets: An Effective Way to Explore Efficient CO

© 2016 American Chemical Society. A novel methodology to explore efficient CO2 adsorbent is developed by the stabilization of layered double oxide (LDO) in the hybrid matrix of re... [more]

© 2016 American Chemical Society. A novel methodology to explore efficient CO2 adsorbent is developed by the stabilization of layered double oxide (LDO) in the hybrid matrix of reduced graphene oxide (rG-O) and layered titanate nanosheets. The electrostatically derived self-assembly between cationic Mg-Al-layered double hydroxide (LDH) nanosheet and anionic graphene oxide (G-O)/layered titanate nanosheets followed by heat treatment at high temperature leads to the cohybridization of LDO (MgO/MgAl2O4) nanocrystals with exfoliated rG-O and layered titanate nanosheets. The incorporation of LDO into the hybrid matrix of rG-O and layered titanate nanosheets is highly effective in increasing its surface area through the formation of mesoporous stacking structure. Of prime importance is that even at very low concentration of titanate (0.3 wt %), an addition of layered titanate nanosheet induces a remarkable surface area expansion of LDO-rG-O nanocomposite from 178 to 330 m2 g-1. This result is attributable to the depression of the self-aggregation of rG-O nanosheets due to the incorporation of layered titanate nanosheet. The resulting LDO-rG-O-layered titanate nanocomposite shows promising CO2 adsorption capability of 1.71 mmol g-1 at 273 K, which is much greater than those of LDO (0.79 mmol g-1) and LDO-rG-O nanocomposites (1.19 mmol g-1), highlighting the remarkable advantage of titanate addition to improve the CO2 adsorptivity of LDO. The present study clearly proves that the restacked assembly of rG-O nanosheet and layered metal oxide one has potential applications as an efficient hybrid matrix for exploring high performance gas adsorbent.

DOI 10.1021/acs.jpcc.6b08065
Citations Scopus - 8
2016 Seo J, Jin X, Kim M, Kim IY, Jo YK, Bera S, et al., 'Exfoliated Metal Oxide Nanosheets as Effective and Applicable Substrates for Atomically Dispersed Metal Nanoparticles with Tailorable Functionalities', Advanced Materials Interfaces, 3 (2016)

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim An effective methodology to stabilize highly dispersed metal nanoparticles is developed by employing the exfoliated 2D meta... [more]

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim An effective methodology to stabilize highly dispersed metal nanoparticles is developed by employing the exfoliated 2D metal oxide nanosheets with variable surface structures as substrates. The selection of appropriate crystal structure of titanate nanosheet is very crucial in stabilizing atomically dispersed Pt nanoparticles through the tuning of chemical interaction between Pt and titanate substrate. A theoretical study using density functional theory calculations confirms the significant influence of the crystal structure of layered titanate nanosheet on the crystal growth behavior of immobilized metal nanoparticle. As a consequence of the good dispersion of Pt nanoparticles, the Pt¿trititanate nanohybrids with stronger interaction show much higher content of atomically dispersed Pt and better catalyst performances than do the Pt¿lepidocrocite titanate ones. The applicability of the present method for other metal species is evidenced by the successful tuning of the crystal size and functionality of Au nanoparticles via immobilization on layered titanate nanosheets. The functionality of Au for surface-enhanced Raman spectroscopy becomes improved by the anchoring on the lepidocrocite-type titanate nanosheet. The present study underscores that the use of the metal oxide 2D nanosheets with appropriate surface structure as substrates is effective in tailoring the crystal growth and the functionalities of immobilized metal nanoparticles.

DOI 10.1002/admi.201600661
Citations Scopus - 1
2016 Kim IY, Lee JM, Hwang EH, Pei YR, Jin WB, Choy JH, Hwang SJ, 'Water-floating nanohybrid films of layered titanate-graphene for sanitization of algae without secondary pollution', RSC Advances, 6 98528-98535 (2016)

© 2016 Royal Society of Chemistry. A novel efficient and safe methodology to sanitize algae in natural water without secondary pollution is developed by fabricating floating graph... [more]

© 2016 Royal Society of Chemistry. A novel efficient and safe methodology to sanitize algae in natural water without secondary pollution is developed by fabricating floating graphene-inorganic hybrid films. Two kinds of floating freestanding hybrid films of layered titanate-graphene with efficient algae-killing functionality are fabricated by vacuum-assisted filtration of mixed colloidal suspensions of reduced graphene oxide (rG-O) nanosheets and exfoliated layered titanate nanosheets. Both the titanate nanosheets with lepidocrocite- and trititanate-type structures form homogeneous colloidal mixtures and hybrid freestanding films with rG-O nanosheets. The incorporation of a layered titanate nanosheet enhances the algae-killing activity of the graphene freestanding film, highlighting the beneficial role of photocatalytically-active titanate nanosheet. In comparison to the trititanate nanosheet, the lepidocrocite-type titanate nanosheet is more effective as a building block for enhancing the algae-killing activity of graphene film and for forming a novel nanoblade structure on the surface of the graphene film. The observed high sterilization functionality of the present layered titanate-graphene hybrid films is attributable to both the formation of the novel sharp nanoblade structure and the photocatalytic activity of layered titanate. The present result underscores that hybridization between graphene and photocatalytically-active inorganic nanosheets can provide a powerful way to explore pollution-free recoverable matrix efficient for removing harmful microorganisms in natural water.

DOI 10.1039/c6ra24140a
Citations Scopus - 4
2016 Kim TW, Kim IY, Park DH, Choy JH, Hwang SJ, 'Highly stable nanocontainer of APTES-anchored layered titanate nanosheet for reliable protection/recovery of nucleic acid', Scientific Reports, 6 (2016)

A universal technology for the encapsulative protection of unstable anionic species by highly stable layered metal oxide has been developed via the surface modification of a metal... [more]

A universal technology for the encapsulative protection of unstable anionic species by highly stable layered metal oxide has been developed via the surface modification of a metal oxide nanosheet. The surface anchoring of (3-aminopropyl)triethoxysilane (APTES) on exfoliated titanate nanosheet yields a novel cationic metal oxide nanosheet, which can be universally used for the hybridization with various biological and inorganic anions. The encapsulation of deoxyribonucleic acid (DNA) in the cationic APTES-anchored titanate lattice makes possible the reliable long-term protection of DNA against enzymatic, chemical, and UVâ 'vis light corrosions. The encapsulated DNA can be easily released from the titanate lattice via sonication, underscoring the functionality of the cationic APTES-anchored titanate nanosheet as a stable nanocontainer for DNA. The APTES-anchored titanate nanosheet can be also used as an efficient CO 2 adsorbent and a versatile host material for various inorganic anions like polyoxometalates, leading to the synthesis of novel intercalative nanohybrids with unexplored properties and useful functionalities.

DOI 10.1038/srep21993
Citations Scopus - 9
2015 Lee JM, Jin HB, Kim IY, Jo YK, Hwang JW, Wang KK, et al., 'A Crucial Role of Rh Substituent Ion in Photoinduced Internal Electron Transfer and Enhanced Photocatalytic Activity of CdS-Ti

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. The photocatalytic activity and photostability of CdS quantum dot (QD) can be remarkably enhanced by hybridization with Rh... [more]

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. The photocatalytic activity and photostability of CdS quantum dot (QD) can be remarkably enhanced by hybridization with Rh-substituted layered titanate nanosheet even at very low Rh substitution rate (<1%). Mesoporous CdS-Ti(5.2-x)/6Rhx/2O2 nanohybrids are synthesized by a self-assembly of exfoliated Ti(5.2-x)/6Rhx/2O2 nanosheets with CdS QDs. The partial substitution of Rh3+/Rh4+ ions for Ti4+ ions in layered titanate is quite effective in enhancing an electronic coupling between hybridized CdS and titanate components via the formation of interband Rh 4d states. A crucial role of Rh substituent ion in the internal electron transfer is obviously evidenced from in situ X-ray absorption spectroscopy showing the elongation of (RhO) bond under visible light irradiation. This is the first spectroscopic evidence for the important role of substituent ion in the photoinduced electron transfer of hybrid-type photocatalyst. The CdS-Ti(5.2-x)/6Rhx/2O2 nanohybrids show much higher photocatalytic activity for H2 production and better photostability than do CdS and unsubstituted CdS-TiO2 nanohybrid. This result is ascribable to the enhancement of visible light absorptivity, the depression of electron-hole recombination, and the enhanced hole curing of CdS upon Rh substitution. The present study underscores that the hybridization with composition-controlled inorganic nanosheet provides a novel efficient methodology to optimize the photo-related functionalities of semiconductor nanocrystal.

DOI 10.1002/smll.201501806
Citations Scopus - 7
2015 Kim IY, Seo J, Oh SM, Patil SB, Hwang SJ, 'In Situ Formation of Conductive Metal Sulfide Domain in Metal Oxide Matrix: An Efficient Way to Improve the Electrochemical Activity of Semiconducting Metal Oxide', Advanced Functional Materials, 25 4948-4955 (2015)

© 2015 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim. A new effective way to improve the electrochemical activity of semiconducting metal oxide is developed by the in situ form... [more]

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. A new effective way to improve the electrochemical activity of semiconducting metal oxide is developed by the in situ formation of conductive metal sulfide domain in the metal oxide matrix. The Li<inf>0.96</inf>Ti<inf>1.08</inf>S<inf>2</inf>-Li<inf>4</inf>Ti<inf>5</inf>O<inf>12</inf> nanocomposites with tunable compositions and electrical properties are synthesized by the reaction of Li<inf>4</inf>Ti<inf>5</inf>O<inf>12</inf> with CS<inf>2</inf> at elevated temperature. The resulting incorporation of conductive Li<inf>0.96</inf>Ti<inf>1.08</inf>S<inf>2</inf> domain in the Li<inf>4</inf>Ti<inf>5</inf>O<inf>12</inf> matrix is effective in enhancing the electrical conductivity and electrode activity of semiconducting lithium titanate. As anode materials for lithium ion batteries, the obtained Li<inf>0.96</inf>Ti<inf>1.08</inf>S<inf>2</inf>-Li<inf>4</inf>Ti<inf>5</inf>O<inf>12</inf> nanocomposites show much greater discharge capacity and better rate characteristics than does the pristine Li<inf>4</inf>Ti<inf>5</inf>O<inf>12</inf>. The usefulness of the present method is further evidenced from the improvement of the electrochemical activity of semiconducting CsTi<inf>2</inf>NbO<inf>7</inf> after the reaction with CS<inf>2</inf>. The present study clearly demonstrates the in situ formation of conductive metal sulfide domain using CS<inf>2</inf> liquid can provide an efficient and universal way to improve the electrode functionality of semiconducting metal oxide.

DOI 10.1002/adfm.201501478
Citations Scopus - 10
2015 Park J, Kim IY, Patel M, Moon HJ, Hwang SJ, Jeong B, '2D and 3D Hybrid Systems for Enhancement of Chondrogenic Differentiation of Tonsil-Derived Mesenchymal Stem Cells', Advanced Functional Materials, 25 2573-2582 (2015)

© 2015 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim. 2D/3D hybrid cell culture systems are constructed by increasing the temperature of the thermogelling poly(ethylene glycol)... [more]

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. 2D/3D hybrid cell culture systems are constructed by increasing the temperature of the thermogelling poly(ethylene glycol)-poly(l-alanine) diblock copolymer (PEG-l-PA) aqueous solution in which tonsil tissue-derived mesenchymal stem cells and graphene oxide (GO) or reduced graphene oxide (rGO) are suspended, to 37 'C. The cells exhibit spherical cell morphologies in 2D/3D hybrid culture systems of GO/PEG-l-PA and rGO/PEG-l-PA by using the growth medium. The cell proliferations are 30%-50% higher in the rGO/PEG-l-PA hybrid system than in the GO/PEG-l-PA hybrid system. When chondrogenic culture media enriched with TGF-ß3 is used in the 2D/3D hybrid systems, cells extensively aggregate, and the expression of chondrogenic biomarkers of SOX 9, COL II A1, COL II, and COL X significantly increases in the GO/PEG-l-PA 2D/3D hybrid system as compared with the PEG-l-PA 3D systems and rGO/PEG-l-PA 2D/3D hybrid system, suggesting that the GO/PEG-l-PA 2D/3D hybrid system can be an excellent candidate as a chondrogenic differentiation platform of the stem cell. This paper also suggests that a 2D/3D hybrid system prepared by incorporating 2D materials with various surface biofunctionalities in the in situ forming 3D hydrogel matrix can be a new cell culture system.

DOI 10.1002/adfm.201500299
Citations Scopus - 42
2015 Patil SB, Kim IY, Gunjakar JL, Oh SM, Eom T, Kim H, Hwang SJ, 'Phase Tuning of Nanostructured Gallium Oxide via Hybridization with Reduced Graphene Oxide for Superior Anode Performance in Li-Ion Battery: An Experimental and Theoretical Study', ACS Applied Materials and Interfaces, 7 18679-18688 (2015)

© 2015 American Chemical Society. The crystal phase of nanostructured metal oxide can be effectively controlled by the hybridization of gallium oxide with reduced graphene oxide ... [more]

© 2015 American Chemical Society. The crystal phase of nanostructured metal oxide can be effectively controlled by the hybridization of gallium oxide with reduced graphene oxide (rGO) at variable concentrations. The change of the ratio of Ga 2 O 3 /rGO is quite effective in tailoring the crystal structure and morphology of nanostructured gallium oxide hybridized with rGO. This is the first example of the phase control of metal oxide through a change of the content of rGO hybridized. The calculations based on density functional theory (DFT) clearly demonstrate that the different surface formation energy and Ga local symmetry of Ga 2 O 3 phases are responsible for the phase transition induced by the change of rGO content. The resulting Ga 2 O 3 -rGO nanocomposites show promising electrode performance for lithium ion batteries. The intermediate Li-Ga alloy phases formed during the electrochemical cycling are identified with the DFT calculations. Among the present Ga 2 O 3 -rGO nanocomposites, the material with mixed a-Ga 2 O 3 /ß-Ga 2 O 3 /¿-Ga 2 O 3 phase can deliver the largest discharge capacity with the best cyclability and rate characteristics, highlighting the importance of the control of Ga 2 O 3 /rGO ratio in optimizing the electrode activity of the composite materials. The present study underscores the usefulness of the phase-control of nanostructured metal oxides achieved by the change of rGO content in exploring novel functional nanocomposite materials. (Graph Presented).

DOI 10.1021/acsami.5b05154
Citations Scopus - 20
2015 Jo YK, Kim IY, Kim SJ, Shin SI, Go A, Lee Y, Hwang SJ, 'Non-monotonous dependence of the electrical conductivity and chemical stability of a graphene freestanding film on the degree of reduction', RSC Advances, 5 19259-19263 (2015)

© The Royal Society of Chemistry. The surface morphology, electrical conductivity, and chemical stability of freestanding graphene films can be effectively tailored by controlled ... [more]

© The Royal Society of Chemistry. The surface morphology, electrical conductivity, and chemical stability of freestanding graphene films can be effectively tailored by controlled reduction of graphene oxide (G-O) precursor. The elastic freestanding graphene films with different degree of reduction can be fabricated by vacuum-assisted filtration of reduced graphene oxide (rG-O) nanosheets prepared with different reduction times. The surface morphology and crystal structure of the resulting rG-O films can be tuned with the change of reduction conditions. Of prime importance is that these graphene films do not show a monotonous dependence of electrical conductivity with the concentration of oxygenated functional groups. After the short reduction time of 30 min, the electrical conductivity of the rG-O films becomes saturated with retention of a considerable amount of oxygenated groups, demonstrating the rapid establishment of electron percolation paths. Interestingly, this graphene film with the reduction time of 30 min displays a higher stability with respect to microwave heating than the other films, a result of the depression of microwave absorption by the increase of electrical conductivity and the reinforced dipolar interaction between restacked graphene by the presence of oxygenated functional groups. The present work highlights the importance of controlled reduction conditions in tailoring the transport properties, surface morphology, and chemical stability of rG-O freestanding films. This journal is

DOI 10.1039/c5ra00309a
Citations Scopus - 5
2015 Jin X, Adpakpang K, Young Kim I, Mi Oh S, Lee NS, Hwang SJ, 'An effective way to optimize the functionality of graphene-based nanocomposite: Use of the colloidal mixture of graphene and inorganic nanosheets', Scientific Reports, 5 (2015)

The best electrode performance of metal oxide-graphene nanocomposite material for lithium secondary batteries can be achieved by using the colloidal mixture of layered CoO 2 and g... [more]

The best electrode performance of metal oxide-graphene nanocomposite material for lithium secondary batteries can be achieved by using the colloidal mixture of layered CoO 2 and graphene nanosheets as a precursor. The intervention of layered CoO 2 nanosheets in-between graphene nanosheets is fairly effective in optimizing the pore and composite structures of the Co 3 O 4-graphene nanocomposite and also in enhancing its electrochemical activity via the depression of interaction between graphene nanosheets. The resulting CoO 2 nanosheet-incorporated nanocomposites show much greater discharge capacity of ~1750 mAhg â '1 with better cyclability and rate characteristics than does CoO 2-free Co 3 O 4-graphene nanocomposite (~1100â ¿¿mAhg â '1). The huge discharge capacity of the present nanocomposite is the largest one among the reported data of cobalt oxide-graphene nanocomposite. Such a remarkable enhancement of electrode performance upon the addition of inorganic nanosheet is also observed for Mn 3 O 4-graphene nanocomposite. The improvement of electrode performance upon the incorporation of inorganic nanosheet is attributable to an improved Li + ion diffusion, an enhanced mixing between metal oxide and graphene, and the prevention of electrode agglomeration. The present experimental findings underscore an efficient and universal role of the colloidal mixture of graphene and redoxable metal oxide nanosheets as a precursor for improving the electrode functionality of graphene-based nanocomposites.

DOI 10.1038/srep11057
Citations Scopus - 22
2015 Gu T-H, Gunjakar JL, Kim IY, Patil SB, Lee JM, Jin X, et al., 'Layered Double Hydroxides: Porous Hybrid Network of Graphene and Metal Oxide Nanosheets as Useful Matrix for Improving the Electrode Performance of Layered Double Hydroxides (Small 32/2015)', Small, 11 3841-3841 (2015)
DOI 10.1002/smll.201570192
2015 Lee JM, Jin HB, Kim IY, Jo YK, Hwang J-W, Wang K-K, et al., 'Hybrid Materials: A Crucial Role of Rh Substituent Ion in Photoinduced Internal Electron Transfer and Enhanced Photocatalytic Activity of CdS-Ti(5.2-x)/6Rhx/2O2Nanohybrids (Small 43/2015)', Small, 11 5721-5721 (2015)
DOI 10.1002/smll.201570257
2015 Kim IY, Seo J, Oh SM, Patil SB, Hwang S-J, 'Batteries: In Situ Formation of Conductive Metal Sulfide Domain in Metal Oxide Matrix: An Efficient Way to Improve the Electrochemical Activity of Semiconducting Metal Oxide (Adv. Funct. Mater. 31/2015)', Advanced Functional Materials, 25 4921-4921 (2015)
DOI 10.1002/adfm.201570208
2015 Yang J, Fainblat R, Kwon SG, Muckel F, Yu JH, Terlinden H, et al., 'Route to the Smallest Doped Semiconductor: Mn

© 2015 American Chemical Society. Doping semiconductor nanocrystals with magnetic transition-metal ions has attracted fundamental interest to obtain a nanoscale dilute magnetic se... [more]

© 2015 American Chemical Society. Doping semiconductor nanocrystals with magnetic transition-metal ions has attracted fundamental interest to obtain a nanoscale dilute magnetic semiconductor, which has unique spin exchange interaction between magnetic spin and exciton. So far, the study on the doped semiconductor NCs has usually been conducted with NCs with larger than 2 nm because of synthetic challenges. Herein, we report the synthesis and characterization of Mn2+-doped (CdSe)13 clusters, the smallest doped semiconductors. In this study, single-sized doped clusters are produced in large scale. Despite their small size, these clusters have semiconductor band structure instead of that of molecules. Surprisingly, the clusters show multiple excitonic transitions with different magneto-optical activities, which can be attributed to the fine structure splitting. Magneto-optically active states exhibit giant Zeeman splittings up to elevated temperatures (128 K) with large g-factors of 81(±8) at 4 K. Our results present a new synthetic method for doped clusters and facilitate the understanding of doped semiconductor at the boundary of molecules and quantum nanostructure.

DOI 10.1021/jacs.5b07888
Citations Scopus - 34
2015 Oh SM, Kim IY, Adpakpang K, Hwang SJ, 'The beneficial effect of nanocrystalline and amorphous nature on the anode performance of manganese oxide for lithium ion batteries', Electrochimica Acta, 174 391-399 (2015)

© 2015 Elsevier Ltd. All rights reserved. The effect of the amorphous structure and nanocrystalline nature of metal oxide on its anode performance in lithium ion batteries is inve... [more]

© 2015 Elsevier Ltd. All rights reserved. The effect of the amorphous structure and nanocrystalline nature of metal oxide on its anode performance in lithium ion batteries is investigated with two nanocrystalline and one well-crystallized layered manganese oxides. X-ray amorphous manganese oxide nanocrystals are synthesized by soft-chemical redox reactions using reducing agents of KBH<inf>4</inf> and LiI at room temperature, whereas well-crystallized layered manganese oxide is obtained by solid state reaction at elevated temperature. Although both of the amorphous manganese oxides lack a long-range structural order, they are crystallized with a layered MnO<inf>2</inf>-type local structure, which is nearly identical to the crystal structure of the well-crystallized K<inf>0.45</inf>MnO<inf>2</inf>. In comparison with the well-crystallized K<inf>0.45</inf>MnO<inf>2</inf>, both the amorphous manganese oxides commonly possess smaller particle sizes with larger surface areas and better homogeneity of composite structure. The amorphous manganese oxide nanocrystals show better anode performance with greater discharge capacity for lithium ion batteries than does the well-crystallized K<inf>0.45</inf>MnO<inf>2</inf>, which is attributable to the greater surface area, higher structural and electrochemical stability, more homogeneous composite structure, and better charge-transfer characteristics of the amorphous materials. This result highlights the merit of the nanocrystalline and amorphous nature for optimizing the electrode performance of manganese oxide. The present solution-based redox reaction can provide a facile, economic, and scalable route for synthesizing efficient manganese-based anode materials for lithium ion batteries.

DOI 10.1016/j.electacta.2015.06.014
Citations Scopus - 9
2015 Gunjakar JL, Kim IY, Hwang SJ, 'Efficient hybrid-type CO

Copyright © 2015 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim. Porous nanohybrids of cationic Mg-Al-LDH 2D nanosheets and anionic polyoxometalate (POM, V10O286- and W7O246-) 0... [more]

Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Porous nanohybrids of cationic Mg-Al-LDH 2D nanosheets and anionic polyoxometalate (POM, V10O286- and W7O246-) 0D nanoclusters are synthesized by an exfoliation-reassembling process. The electrostatically derived reassembling between two kinds of nanostructures yields a layer-by-layer-ordered intercalation structure with porous structures composed of mesopores and micropores. The hybridization with POM leads to the remarkable enhancement of CO2 adsorption capacity (adsorptivity) of Mg-Al-LDH by about 10-fold. Of prime importance is that the CO2 adsorptivity of the nanohybrid is strongly dependent on the type of guest POM species, strongly suggesting that the CO2 adsorptivity of the LDH-based nanohybrid materials can be optimized by ones selection of guest species. The present study clearly demonstrates that the exfoliation-reassembling method is quite effective at enabling synthesis of new LDH nanosheet-based hybrid materials with improved CO2 adsorption capabilities.

DOI 10.1002/ejic.201402480
Citations Scopus - 14
2015 Gu TH, Gunjakar JL, Kim IY, Patil SB, Lee JM, Jin X, et al., 'Porous Hybrid Network of Graphene and Metal Oxide Nanosheets as Useful Matrix for Improving the Electrode Performance of Layered Double Hydroxides', Small, 11 3921-3931 (2015)

© 2015 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim. Mesoporous hybrid network of reduced graphene oxide (rG-O) and layered MnO&lt;inf&gt;2&lt;/inf&gt; nanosheets could act as... [more]

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Mesoporous hybrid network of reduced graphene oxide (rG-O) and layered MnO<inf>2</inf> nanosheets could act as an efficient immobilization matrix for improving the electrochemical activity of layered double hydroxide (LDH). The control of MnO<inf>2</inf>/rG-O ratio is crucial in optimizing the porous structure and electrical conductivity of the resulting hybrid structure. The immobilization of Co-Al-LDH on hybrid MnO<inf>2</inf>/rG-O network is more effective in enhancing its electrode activity compared with that of on pure rG-O network. The Co-Al-LDH-rG-O-MnO<inf>2</inf> nanohybrid deliveres a greater specific capacitance than does MnO<inf>2</inf>-free Co-Al-LDH-rG-O nanohybrid. The beneficial effect of MnO<inf>2</inf> incorporation on the electrode performance of nanohybrid is more prominent for higher current density and faster scan rate, underscoring the significant enhancement of the electron transport of Co-Al-LDH-rG-O. This is supported by electrochemical impedance spectroscopy. The present study clearly demonstrates the usefulness of the porously assembled hybrid network of graphene and metal oxide nanosheets as an effective platform for exploring efficient LDH-based functional materials.

DOI 10.1002/smll.201500286
Citations Scopus - 24
2014 Jo YK, Kim IY, Lee JM, Nahm S, Choi JW, Hwang SJ, 'Surface-anchored CdS@Ag

The surface anchoring of CdS on the surface of Ag3PO4 nanoparticle is achieved by an electrostatically-derived assembly between negatively-charged Ag3PO4 nanoparticles and positiv... [more]

The surface anchoring of CdS on the surface of Ag3PO4 nanoparticle is achieved by an electrostatically-derived assembly between negatively-charged Ag3PO4 nanoparticles and positively-charged CdS quantum dots (QDs). The composite formation between Ag3PO4 and CdS nanoparticles gives rise not only to an enhancement of visible light absorption but also to a notable depression of photoluminescence signal, confirming the strong electronic coupling between the two components. The present CdS@Ag3PO4 nanocomposite displays higher visible light photocatalytic activity than do the precursors Ag3PO4 and CdS, demonstrating the usefulness of electrostatically-derived assembly in exploring highly efficient photocatalyst material. © 2013 Published by Elsevier B.V.

DOI 10.1016/j.matlet.2013.09.091
Citations Scopus - 29
2014 Jo YK, Kim IY, Gunjakar JL, Lee JM, Lee NS, Lee SH, Hwang SJ, 'Unique properties of 2 D layered titanate nanosheets as a building block for the optimization of the photocatalytic activity and photostability of TiO

In comparison with the hybridization with 0D TiO2 nanoparticle, 2D layered TiO2 nanosheets are much more effective in the improvement of the photocatalytic activity and photostabi... [more]

In comparison with the hybridization with 0D TiO2 nanoparticle, 2D layered TiO2 nanosheets are much more effective in the improvement of the photocatalytic activity and photostability of semiconducting compounds. The 2D TiO2-Ag3PO4 nanohybrid described in this paper shows a greater decrease in the electron-hole recombination upon hybridization and a stronger chemical interaction between the components than the 0D homologue. This result confirms the benefits of 2D layered TiO 2 nanosheets as a building block for efficient hybrid-type photocatalyst materials. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI 10.1002/chem.201402726
Citations Scopus - 16
2014 Park S, Lee JM, Jo YK, Kim IY, Hwang SJ, 'A facile exfoliation-crystal growth route to multicomponent Ag

Multicomponent Ag 2 CO 3 /Ag-layered Ti 5 NbO 14 nanohybrids are synthesized by the crystal growth of silver carbonate on the surface of exfoliated layered titanoniobate 2D nanosh... [more]

Multicomponent Ag 2 CO 3 /Ag-layered Ti 5 NbO 14 nanohybrids are synthesized by the crystal growth of silver carbonate on the surface of exfoliated layered titanoniobate 2D nanosheets. In the obtained nanohybrids, the spherical Ag 2 CO 3 nanoparticles with a size of 5-10 nm are immobilized on the surface of the titanoniobate nanosheets with partial formation of neutral Ag metal caused by electron transfer from anionic titanoniobate nanosheets to silver cations. An electronic coupling between Ag 2 CO 3 /Ag and Ti 5 NbO 14 nanosheets leads to a remarkable enhancement of visible light absorption and a significant depression of electron-hole recombination. The present Ag 2 CO 3 /Ag-layered Ti 5 NbO 14 nanohybrids show much higher visible light photocatalytic activity than the unhybridized Ag 2 CO 3 , underscoring the beneficial effect of hybridization with metal oxide nanosheets on the photocatalytic activity of silver oxosalts. Before and after the photoreaction, the crystal structure and crystal morphology of the Ag 2 CO 3 /Ag-layered Ti 5 NbO 14 nanohybrids remain unchanged, highlighting the excellent photostability of these materials. All the present experimental findings clearly demonstrate the usefulness of the exfoliation-crystal growth method in exploring novel efficient visible light active photocatalysts. This journal is © the Partner Organisations 2014.

DOI 10.1039/c4dt00018h
Citations Scopus - 14
2014 Kim IY, Park S, Kim H, Park S, Ruoff RS, Hwang SJ, 'Strongly-coupled freestanding hybrid films of graphene and layered titanate nanosheets: An effective way to tailor the physicochemical and antibacterial properties of graphene film', Advanced Functional Materials, 24 2288-2294 (2014)

An effective way to tailor the physicochemical properties of graphene film is developed by combining colloidal suspensions of reduced graphene oxide (rG-O) nanosheets and exfoliat... [more]

An effective way to tailor the physicochemical properties of graphene film is developed by combining colloidal suspensions of reduced graphene oxide (rG-O) nanosheets and exfoliated layered titanate nanosheets for the fabrication of freestanding hybrid films comprised of stacked and overlapped nanosheets. A flow-directed filtration of such mixed colloidal suspensions yields freestanding hybrid films comprised of strongly-coupled rG-O and titanate nanosheets with tunable chemical composition. This is the first example of highly flexible hybrid films composed of graphene and metal oxide nanosheets. The intimate incorporation of layered titanate nanosheets into the graphene film gives rise not only to an increase of mechanical strength but also to increased surface roughness, chemical stability, and hydrophilicity; thus, the physicochemical properties of the graphene film can be tuned by hybridization with inorganic nanosheets. These freestanding hybrid films of rG-O-layered titanate show unprecedentedly high antibacterial property, resulting in the complete sterilization of Escherichia coli O157:H7 (¿100%) in the very short time of 15 min. The antibacterial activity of the hybrid film is far superior to that of the pure graphene film, underscoring the beneficial effect of the layered metal oxide nanosheets in improving the functionality of the graphene film. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI 10.1002/adfm.201303040
Citations Scopus - 57
2014 Lee JM, Gunjakar JL, Ham Y, Kim IY, Domen K, Hwang S-J, 'A Linker-Mediated Self-Assembly Method to Couple Isocharged Nanostructures: Layered Double Hydroxide-CdS Nanohybrids with High Activity for Visible-Light-Induced H2Generation', Chemistry - A European Journal, 20 17004-17010 (2014)
DOI 10.1002/chem.201404472
2014 Gunjakar JL, Kim IY, Lee JM, Jo YK, Hwang SJ, 'Exploration of nanostructured functional materials based on hybridization of inorganic 2D nanosheets', Journal of Physical Chemistry C, 118 3847-3863 (2014)

The 2D nanosheets of layered inorganic solids prepared by soft-chemical exfoliation reaction can be used as effective building blocks for hybridization with inorganic, organic, bi... [more]

The 2D nanosheets of layered inorganic solids prepared by soft-chemical exfoliation reaction can be used as effective building blocks for hybridization with inorganic, organic, bio-, and polymer molecules/nanostructures. In comparison with graphene nanosheets, the 2D inorganic nanosheets boast much higher tunability in their chemical composition and physicochemical properties, leading to the creation of unexpected novel functionalities upon hybridization. Despite such unique and intriguing advantages of inorganic nanosheets, there are still only limited numbers of studies regarding the inorganic nanosheet-based hybrid materials. This Feature Article focuses on fundamental aspects of diverse synthetic strategies of the 2D nanosheet-based nanohybrids such as electrostatically derived reassembling, layer-by-layer deposition, crystal growth on the surface sites of nanosheets, and so on. Also, diverse functionalities of these 2D nanohybrid materials are discussed with an emphasis on the energy and environmental applications such as Li-ion batteries, supercapacitors, photocatalysts, fuel cells, and greenhouse gas capture. A prospect for the exploration of novel inorganic 2D nanosheet-based functional materials is provided along with new strategies to optimize the functionality of 2D inorganic nanosheets and their nanohybrids. © 2014 American Chemical Society.

DOI 10.1021/jp410626y
Citations Scopus - 74
2014 Kim IY, Jo YK, Lee JM, Wang L, Hwang SJ, 'Unique advantages of exfoliated 2D nanosheets for tailoring the functionalities of nanocomposites', Journal of Physical Chemistry Letters, 5 4149-4161 (2014)

© 2014 American Chemical Society. Hybridization with exfoliated two-dimensional (2D) nanosheets provides a very effective and powerful way not only to control the physicochemical ... [more]

© 2014 American Chemical Society. Hybridization with exfoliated two-dimensional (2D) nanosheets provides a very effective and powerful way not only to control the physicochemical properties of hybridized species but also to explore nanocomposites with novel functionalities. Deliberate coupling between the hybridized species is critically important in maximizing the effect of hybridization on the physicochemical properties and functionality of hybridized components. The very small thickness and extremely large surface of exfoliated 2D nanosheets render these materials ideal candidates for achieving a strong coupling with diverse guest species. This Perspective focuses on the unique characteristics of exfoliated 2D nanosheets as building blocks for designing hybrid materials. Several intriguing examples of strong interaction between exfoliated 2D nanosheets and hybridized species are summarized with an emphasis on the effective control of electronic, optical, structural, and morphological characteristics. An outlook on the future research directions is provided along with new strategies to maximize the coupling in the 2D nanosheet-based hybrid materials.

DOI 10.1021/jz502038g
Citations Scopus - 58
2014 Kim SJ, Kim IY, Patil SB, Oh SM, Lee NS, Hwang SJ, 'Composition-tailored 2D Mn

Composition-tailored Mn1-xRuxO2 2D nanosheets and their reassembled nanocomposites with mesoporous stacking structure are synthesized by a soft-chemical exfoliation reaction and t... [more]

Composition-tailored Mn1-xRuxO2 2D nanosheets and their reassembled nanocomposites with mesoporous stacking structure are synthesized by a soft-chemical exfoliation reaction and the subsequent reassembling of the exfoliated nanosheets with Li+ cations, respectively. The tailoring of the chemical compositions of the exfoliated Mn1-xRuxO2 2D nanosheets and their lithiated nanocomposites can be achieved by adopting the Ru-substituted layered manganese oxides as host materials for exfoliation reaction. Upon the exfoliation-reassembling process, the substituted ruthenium ions remain stabilized in the layered Mn1-xRuxO2 lattice with mixed Ru3+/Ru4+ oxidation state. The reassembled Li-Mn1-xRuxO2 nanocomposites show promising pseudocapacitance performance with large specific capacitances of approximately 330 Fg-1 for the second cycle and approximately 360 Fg-1 for the 500th cycle and excellent cyclability, which are superior to those of the unsubstituted Li-MnO2 homologue and many other MnO 2-based materials. Electrochemical impedance spectroscopy analysis provides strong evidence for the enhancement of the electrical conductivity of 2D nanostructured manganese oxide upon Ru substitution, which is mainly responsible for the excellent electrode performance of Li-Mn 1-xRuxO2 nanocomposites. The results underscore the powerful role of the composition-controllable metal oxide 2D nanosheets as building blocks for exploring efficient electrode materials. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI 10.1002/chem.201304009
Citations Scopus - 12
2013 Jo KY, Han SY, Lee JM, Kim IY, Nahm S, Choi JW, Hwang SJ, 'Remarkable enhancement of the electrode performance of nanocrystalline LiMn

A facile solvothermal way to immobilize nanocrystalline LiMn 2O4 on the surface of graphene nanosheets is developed to improve the functionality of lithium manganate as lithium in... [more]

A facile solvothermal way to immobilize nanocrystalline LiMn 2O4 on the surface of graphene nanosheets is developed to improve the functionality of lithium manganate as lithium intercalation electrode. A solvothermal treatment for the colloidal mixture of graphene oxide (GO) nanosheets and LiMn2O4 nanocrystals gives rise not only to the reduction of GO to reduced graphene oxide (RGO) but also to the immobilization of lithium manganate nanoparticles on the surface of RGO nanosheets. According to powder X-ray diffraction and electron microscopic analyses, the crystal structure and morphology of spinel lithium manganate remain intact upon the composite formation with the RGO nanosheets. The application of larger aldehyde molecule as a reductant leads to the increase of crystallinity and the lowering of Mn oxidation state for the pristine LiMn 2O4 and its nanocomposite with the RGO nanosheets. The present LiMn2O4-RGO nanocomposites display promising cathode performances for lithium rechargeable batteries, which are much superior to those of the pristine LiMn2O4 nanocrystals. The observed enhancement of electrode performance upon the composite formation with the RGO nanosheets is attributable both to the improvement of the surface ion transport of nanocrystalline lithium manganate and to the increase of electrical conductivity. The present experimental findings demonstrate that the solvothermal treatment with RGO nanosheets provides an effective way of improving the electrochemical activity of nanocrystalline lithium metal oxides. © 2013 Elsevier Ltd.

DOI 10.1016/j.electacta.2013.01.022
Citations Scopus - 19
2013 Oh SM, Kim IY, Kim SJ, Jung W, Hwang SJ, 'A phase transformation route to Fe

Intimately mixed nanocomposite of Fe 2 O 3 and Mn 3 O 4 is synthesized by an electrostatically-derived self-assembly between exfoliated MnO 2 nanosheets and Fe cations, which is f... [more]

Intimately mixed nanocomposite of Fe 2 O 3 and Mn 3 O 4 is synthesized by an electrostatically-derived self-assembly between exfoliated MnO 2 nanosheets and Fe cations, which is followed by heat-treatment at elevated temperature. The as-prepared Fe-layered MnO 2 nanocomposite experiences phase transformations into Fe-substituted Mn 3-x Fe x O 4 nanoparticle at 450 C and Fe 2 O 3 -Mn 3 O 4 nanocomposite at 650 C. The Fe 2 O 3 -Mn 3 O 4 nanocomposite shows better performance as anode material for lithium ion batteries than the Fe-substituted Mn 3-x Fe x O 4 nanoparticle, indicating the beneficial effect of composite formation on the electrode performance of 3d metal oxide. The present finding underscores that a self-assembly between exfoliated metal oxide nanosheets and metal cations can provide useful precursor for efficient composite electrode materials. © 2013 Elsevier B.V.

DOI 10.1016/j.matlet.2013.05.050
Citations Scopus - 7
2013 Sung DY, Gunjakar JL, Kim TW, Kim IY, Lee YR, Hwang SJ, 'Graphene-assisted room-temperature synthesis of 2D nanostructured hybrid electrode materials: Dramatic acceleration of the formation rate of 2D metal oxide nanoplates induced by reduced graphene oxide nanosheets', Chemistry - A European Journal, 19 7109-7117 (2013)

A new prompt room temperature synthetic route to 2D nanostructured metal oxide-graphene-hybrid electrode materials can be developed by the application of colloidal reduced graphen... [more]

A new prompt room temperature synthetic route to 2D nanostructured metal oxide-graphene-hybrid electrode materials can be developed by the application of colloidal reduced graphene oxide (RGO) nanosheets as an efficient reaction accelerator for the synthesis of d-MnO 2 2D nanoplates. Whereas the synthesis of the 2D nanostructured d-MnO 2 at room temperature requires treating divalent manganese compounds with persulfate ions for at least 24h, the addition of RGO nanosheet causes a dramatic shortening of synthesis time to 1h, underscoring its effectiveness for the promotion of the formation of 2D nanostructured metal oxide. To the best of our knowledge, this is the first example of the accelerated synthesis of 2D nanostructured hybrid material induced by the RGO nanosheets. The observed acceleration of nanoplate formation upon the addition of RGO nanosheets is attributable to the enhancement of the oxidizing power of persulfate ions, the increase of the solubility of precursor MnCO 3 , and the promoted crystal growth of d-MnO 2 2D nanoplates. The resulting hybridization between RGO nanosheets and d-MnO 2 nanoplates is quite powerful not only in increasing the surface area of manganese oxide nanoplate but also in enhancing its electrochemical activity. Of prime importance is that the present d-MnO 2 -RGO nanocomposites show much superior electrode performance over most of 2D nanostructured manganate systems including a similar porous assembly of RGO and layered MnO 2 nanosheets. This result underscores that the present RGO-assisted solution-based synthesis can provide a prompt and scalable method to produce nanostructured hybrid electrode materials. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI 10.1002/chem.201300001
Citations Scopus - 16
2013 Kim TW, Kim IY, Jung TS, Ko CH, Hwang SJ, 'A new type of efficient CO

A new type of efficient CO 2 absorbent with improved thermal stability is synthesized via self-assembly between 2D inorganic nanosheets and two kinds of 0D inorganic nanoclusters.... [more]

A new type of efficient CO 2 absorbent with improved thermal stability is synthesized via self-assembly between 2D inorganic nanosheets and two kinds of 0D inorganic nanoclusters. In these self-assembled nanohybrids, the nanoclusters of CdO and Cr 2 O 3 are commonly interstratified with layered titanate nanosheets, leading to the formation of highly microporous pillared structure with increased basicity of pore wall. The co-pillaring of basic CdO with Cr 2 O 3 is fairly effective at increasing a proportion of micropores and reactivity for CO 2 molecules and at improving the thermal stability of the resulting porous structure. Of prime importance is that the present inorganic-pillared nanohybrids show highly efficient CO 2 adsorption capacity, which is much superior to those of many other absorbents and compatible to those of CO 2 adsorbing metal-organic framework (MOF) compounds. Taking into account an excellent thermal stability of the present nanohybrids, these materials are very promising CO 2 adsorbents usable at elevated temperature. This is the first example of efficient CO 2 adsorbent from pillared materials. The co-pillaring of basic metal oxide nanoclusters employed in this study can provide a very powerful way of developing thermally stable CO 2 adsorbents from many known pillared systems. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI 10.1002/adfm.201300071
Citations Scopus - 18
2013 Shin SI, Go A, Kim IY, Lee JM, Lee Y, Hwang SJ, 'A beneficial role of exfoliated layered metal oxide nanosheets in optimizing the electrocatalytic activity and pore structure of Pt-reduced graphene oxide nanocomposites', Energy and Environmental Science, 6 608-617 (2013)

Mesoporous nanocomposites of Pt-reduced graphene oxide (RGO)-layered titanate are synthesized by the reaction of a mixture of exfoliated layered titanate nanosheets, graphene oxid... [more]

Mesoporous nanocomposites of Pt-reduced graphene oxide (RGO)-layered titanate are synthesized by the reaction of a mixture of exfoliated layered titanate nanosheets, graphene oxide nanosheets, and H<inf>2</inf>PtCl <inf>6</inf> with NaBH<inf>4</inf> to investigate the effect of layered metal oxide nanosheets on the electrocatalyst performance of Pt-RGO nanocomposites. The obtained ternary nanocomposites are composed of a porous stacking assembly of layered titanate/RGO nanosheets with well-dispersed Pt nanocrystals whose particle size becomes smaller with the increase of titanate content. The incorporation of layered titanate nanosheets into the Pt-RGO nanocomposite induces a marked increase of surface area through the frustration of a strong p-p interaction between RGO nanosheets by the intervention of titanate nanosheets. In addition, the incorporation of layered titanate nanosheets gives rise to a remarkable improvement of electrocatalytic activity for oxygen reduction reaction (ORR). Of prime importance is that the present nanocomposites show a more positive onset potential for ORR than commercial Pt/carbon catalysts, underscoring a powerful role of titanate nanosheets in optimizing the electrocatalyst performance of Pt-RGO nanocomposites. This is the first report showing the usefulness of metal oxide nanosheets as an effective additive for enhancing the electrocatalyst performance of platinum nanoparticles. The observed enhancement of electrocatalytic activity upon the addition of titanate nanosheets is attributable to the decrease of Pt crystal size, the increase of surface area, and the increase of surface hydrophilicity. The present findings clearly demonstrate that the incorporation of layered titanate nanosheets is quite effective in improving the electrocatalytic functionality of Pt-RGO nanocomposites. © The Royal Society of Chemistry 2013.

DOI 10.1039/c2ee22739h
Citations Scopus - 48
2013 Gunjakar JL, Kim IY, Lee JM, Lee NS, Hwang SJ, 'Self-assembly of layered double hydroxide 2D nanoplates with graphene nanosheets: An effective way to improve the photocatalytic activity of 2D nanostructured materials for visible light-induced O

Highly efficient photocatalysts for visible light-induced O 2 generation are synthesized via an electrostatically derived self-assembly of Zn-Cr-LDH 2D nanoplates with graphene 2D... [more]

Highly efficient photocatalysts for visible light-induced O 2 generation are synthesized via an electrostatically derived self-assembly of Zn-Cr-LDH 2D nanoplates with graphene 2D nanosheets. In the obtained nanohybrids, the positively charged Zn-Cr-LDH nanoplates are immobilized on the surface of negatively charged graphene nanosheets with the formation of a highly porous stacked structure. A strong electronic coupling of the subnanometer-thick Zn-Cr-LDH nanoplates with reduced graphene oxide (RGO)/graphene oxide (GO) nanosheets gives rise not only to the prominent increase of visible light absorption but also to a remarkable depression of the photoluminescence signal. The self-assembled Zn-Cr-LDH-RGO nanohybrids display an unusually high photocatalytic activity for visible light-induced O 2 generation with a rate of ~1.20 mmol h -1 g -1 , which is far superior to that of the pristine Zn-Cr-LDH material (~0.67 mmol h -1 g -1 ). The fact that pristine Zn-Cr-LDH is one of the most effective visible light photocatalysts for O 2 production with unusually high quantum efficiency of 61% at ¿ = 410 nm highlights the excellent functionality of the Zn-Cr-LDH-RGO nanohybrids as visible light active photocatalysts. The Zn-Cr-LDH-RGO nanohybrid shows a higher photocatalytic activity than the Zn-Cr-LDH-GO nanohybrid, providing strong evidence for the superior advantage of the hybridization with RGO. The present findings clearly demonstrate that graphene nanosheets can be used as an effective platform for improving the photocatalytic activity of 2D nanostructured inorganic solids. © 2013 The Royal Society of Chemistry.

DOI 10.1039/c3ee23989f
Citations Scopus - 140
2013 Jin X, Kim IY, Jo YK, Bettis JL, Koo HJ, Whangbo MH, Hwang SJ, 'A crucial role of bond covalency competition in determining the bandgap and photocatalytic performance of silver oxosalts', Journal of Physical Chemistry C, 117 26509-26516 (2013)

The optical bandgaps, the surface charges, and the photocatalytic activities of the silver oxosalts Ag 3 AsO 4 , Ag 2 CO 3 , Ag 3 PO 4 , Ag 2 SO 4 , and Ag 2 SeO 4 are systematica... [more]

The optical bandgaps, the surface charges, and the photocatalytic activities of the silver oxosalts Ag 3 AsO 4 , Ag 2 CO 3 , Ag 3 PO 4 , Ag 2 SO 4 , and Ag 2 SeO 4 are systematically investigated with several experimental techniques and first principles density functional theory calculations. The trends in the optical bandgaps and the surface charges of these silver oxosalts, Ag x (XO y ) z , are analyzed by considering how the X-O bond covalency affects the charge on the terminal oxygen atoms and the Ag-O bond covalency. The optical bandgaps of Ag x (XO y ) z are well-described by the bond-covalency competition in the Ag-O-X linkages because an increase in the overlap between the O 2s/2p and X ns/np orbitals decreases the overlap between the Ag 4d and O 2s/2p orbitals. The optical bandgap increases linearly with increasing the Z/r ratio of the atom X, a simple measure of the X-O bond covalency. In the photodegradation of charged molecules, the surface charge of Ag x (XO y ) z plays a prominent role and decreases with increasing the Z/r ratio. As expected from the present theoretical predictions, newly investigated Ag 2 SeO 4 exhibits a promising photocatalytic activity under visible light. The Z/r ratio of the central atom X provides an effective measure for predicting the photocatalyst performance and the optical bandgap of silver oxosalts Ag x (XO y ) z . © 2013 American Chemical Society.

DOI 10.1021/jp4101784
Citations Scopus - 9
2013 Jiang S, Kim MG, Kim IY, Hwang SJ, Hur HG, 'Biological synthesis of free-standing uniformed goethite nanowires by Shewanella sp. HN-41', Journal of Materials Chemistry A, 1 1646-1650 (2013)

Dissimilatory iron-reducing bacterium Shewanella sp. HN-41 is capable of producing various nanoscale minerals due to its versatile respiratory reduction activities in a range of e... [more]

Dissimilatory iron-reducing bacterium Shewanella sp. HN-41 is capable of producing various nanoscale minerals due to its versatile respiratory reduction activities in a range of elements. Herein we report that free-standing uniformed goethite nanowires are synthesized by Shewanella sp. HN-41 under well-controlled bacterial culture conditions. A comparative investigation revealed that the bacterial transformation of iron nanostructures by strain HN-41 was significantly affected by the amount of akaganeite precursors and Fe(ii) in liquid cultures. Electric analysis of the bacterial goethite nanowires shows a meaningful initial charge-discharge capacity for Li-ion storage, suggesting that the facile biological control for the morphological change of nanomaterials can surely give a new opportunity for the development of Li-rechargeable battery electrode materials. © 2013 The Royal Society of Chemistry.

DOI 10.1039/c2ta00466f
Citations Scopus - 12
2013 Lee JW, Son DY, Ahn TK, Shin HW, Kim IY, Hwang SJ, et al., 'Quantum-dot-sensitized solar cell with unprecedentedly high photocurrent', Scientific Reports, 3 (2013)

The reported photocurrent density (J SC) of PbS quantum dot (QD)-sensitized solar cell was less than 19 mA/cm2 despite the capability to generate 38 mA/cm2, which results from ine... [more]

The reported photocurrent density (J SC) of PbS quantum dot (QD)-sensitized solar cell was less than 19 mA/cm2 despite the capability to generate 38 mA/cm2, which results from inefficient electron injection and fast charge recombination. Here, we report on a PbS:Hg QD-sensitized solar cell with an unprecedentedly high J SC of 30 mA/cm2. By Hg 2+ doping into PbS, J SC is almost doubled with improved stability. Femtosecond transient study confirms that the improved J SC is due to enhanced electron injection and suppressed charge recombination. EXAFS reveals that Pb-S bond is reinforced and structural disorder is reduced by interstitially incorporated Hg2+, which is responsible for the enhanced electron injection, suppressed recombination and stability. Thanks to the extremely high J SC, power conversion efficiency of 5.6% is demonstrated at one sun illumination.

DOI 10.1038/srep01050
Citations Scopus - 207
2013 Gunjakar JL, Kim TW, Kim IY, Lee JM, Hwang SJ, 'Highly efficient visible light-induced O

Unusually high photocatalytic activity of visible light-induced O 2 generation can be achieved by electrostatically-derived self-Assembly between exfoliated Zn-Cr-LDH 2D nanosheet... [more]

Unusually high photocatalytic activity of visible light-induced O 2 generation can be achieved by electrostatically-derived self-Assembly between exfoliated Zn-Cr-LDH 2D nanosheets and POM 0D nanoclusters (W 7 O 24 62 and V 10 O 28 62 ) acting as an electron acceptor. This self-Assembly can provide a high flexibility in the control of the chemical composition and pore structure of the resulting LDH-based nanohybrids. The hybridization with POM nanoclusters remarkably enhances the photocatalytic activity of the pristine Zn-Cr-LDH, which is attributable to the formation of porous structure and depression of charge recombination. Of prime interest is that the excellent photocatalytic activity of the as-prepared Zn-Cr-LDH-POM nanohybrid for visible light-induced O2 generation can be further enhanced by calcination at 200 6C, leading to the very high apparent quantum yield of ,75.2% at 420 nm. The present findings clearly demonstrate that the self-Assembly of LDH-POM is fairly powerful in synthesizing novel LDH-based porous nanohybrid photocatalyst for visible light-induced O2 generation.

DOI 10.1038/srep02080
Citations Scopus - 31
2012 Han SY, Kim IY, Lee SH, Hwang SJ, 'Electrochemically active nanocomposites of Li

Electrochemically active nanocomposites consisting of Li 4Ti 5O 12 2D nanosheets and SnO 2 0D nanocrystals are synthesized by the crystal growth of tin dioxide on the surface of 2... [more]

Electrochemically active nanocomposites consisting of Li 4Ti 5O 12 2D nanosheets and SnO 2 0D nanocrystals are synthesized by the crystal growth of tin dioxide on the surface of 2D nanostructured lithium titanate. According to powder X-ray diffraction and electron microscopic analyses, the rutile-structured SnO 2 nanocrystals are stabilized on the surface of spinel-structured Li 4Ti 5O 12 2D nanosheets. The homogeneous hybridization of tin dioxide with lithium titanate is confirmed by elemental mapping analysis. Ti K-edge X-ray absorption near-edge structure and Sn 3d X-ray photoelectron spectroscopy indicate the stabilization of tetravalent titanium ions in the spinel lattice of Li 4Ti 5O 12 and the formation of SnO 2 phase with tetravalent Sn oxidation state. The electrochemical measurements clearly demonstrate the promising functionality of the present nanocomposites as anode for lithium secondary batteries. The Li 4Ti 5O 12-SnO 2 nanocomposites show larger discharge capacity and better cyclability than do the uncomposited Li 4Ti 5O 12 and SnO 2 phases, indicating the synergistic effect of nanocomposite formation on the electrode performance of Li 4Ti 5O 12 and SnO 2. The present experimental findings underscore the validity of 2D nanostructured lithium titanate as a useful platform for the stabilization of nanocrystalline electrode materials and also for the improvement of their functionality. © 2012 Elsevier Ltd.

DOI 10.1016/j.electacta.2012.03.175
Citations Scopus - 15
2012 Han SY, Young Kim I, Hwang SJ, 'Synthesis and electrochemical characterization of 2D nanostructured Li

Two-dimensional (2D) Li 4Ti 5O 12 nanosheets with cubic spinel structure are synthesized via a lithiation process of exfoliated titanate 2D nanosheets and the subsequent heat-trea... [more]

Two-dimensional (2D) Li 4Ti 5O 12 nanosheets with cubic spinel structure are synthesized via a lithiation process of exfoliated titanate 2D nanosheets and the subsequent heat-treatment at elevated temperatures. According to powder X-ray diffraction and field emission-scanning electron microscopy analysis, the obtained lithium titanium oxides show well-developed Bragg reflections of cubic spinel-structured Li 4Ti 5O 12 phase and highly anisotropic 2D plate-like morphology. Ti K-edge X-ray absorption near-edge structure analysis reveals the stabilization of tetravalent titanium ions in the cubic spinel lattice of Li 4Ti 5O 12. The 2D nanostructured Li 4Ti 5O 12 materials display the electrochemical functionality as negative electrode for lithium secondary batteries. The most promising electrode performance is achieved by the heat-treatment of the lithiated titanate at 600 °C, highlighting the importance of heating temperature in optimizing the electrochemical property of the resulting materials. © 2012 ElsevierLtd.Allrightsreserved.

DOI 10.1016/j.jpcs.2011.10.044
Citations Scopus - 11
2012 Lee YR, Kim IY, Kim TW, Lee JM, Hwang SJ, 'Mixed colloidal suspensions of reduced graphene oxide and layered metal oxide nanosheets: Useful precursors for the porous nanocomposites and hybrid films of graphene/metal oxide', Chemistry - A European Journal, 18 2263-2271 (2012)

Homogeneously mixed colloidal suspensions of reduced graphene oxide, or RGO, and layered manganate nanosheets have been synthesized by a simple addition of the exfoliated colloid ... [more]

Homogeneously mixed colloidal suspensions of reduced graphene oxide, or RGO, and layered manganate nanosheets have been synthesized by a simple addition of the exfoliated colloid of RGO into that of layered MnO 2 . The obtained mixed colloidal suspensions with the RGO/MnO 2 ratio of =0.3 show good colloidal stability without any phase separation and a negatively charged state with a zeta (¿) potential of -30 to -40 mV. The flocculation of these mixed colloidal suspensions with lithium cations yields porous nanocomposites of Li/RGO-layered MnO 2 with high electrochemical activity and a markedly expanded surface area of around 70-100 m 2 g -1 . Relative to the Li/RGO and Li/layered MnO 2 nanocomposites (¿116 and ¿167 F g -1 ), the obtained Li/RGO-layered MnO 2 nanocomposites deliver a larger capacitance of approximately 210 F g -1 with good cyclability of around 95-97 % up to the 1000th cycle, thus indicating the positive effect of hybridization on the electrode performances of RGO and lithium manganate. Also, an electrophoretic deposition of the mixed colloidal suspensions makes it possible to easily fabricate uniform hybrid films composed of graphene and manganese oxide. The obtained films show a distinct electrochemical activity and a homogeneous distribution of RGO and MnO 2 . The present experimental findings clearly demonstrate that the utilization of the mixed colloidal suspensions as precursors provides a facile and universal methodology to synthesize various types of graphene/metal oxide hybrid materials. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI 10.1002/chem.201102646
Citations Scopus - 48
2012 Lee JM, Kim IY, Han SY, Kim TW, Hwang SJ, 'Graphene nanosheets as a platform for the 2D ordering of metal oxide nanoparticles: Mesoporous 2D aggregate of anatase TiO

Graphene nanosheets are successfully applied as an effective platform for the 2D ordering of metal oxide nanoparticles. Mesoporous 2D aggregates of anatase TiO 2 nanoparticles are... [more]

Graphene nanosheets are successfully applied as an effective platform for the 2D ordering of metal oxide nanoparticles. Mesoporous 2D aggregates of anatase TiO 2 nanoparticles are synthesized by the heat treatment of the uniformly hybridized nanocomposite of layered titanate-reduced graphene oxide (RGO) at elevated temperatures. The precursor layered titanate-RGO nanocomposite is prepared by self-assembly of anionic RGO nanosheets and cationic TiO 2 nanosols. The calcination of the as-prepared layered titanate-RGO nanocomposite at 500 °C induces a structural and morphological change of layered titanate nanoplates into anatase TiO 2 nanoparticles without significant modification of the RGO nanosheet. Increasing the heating temperature to 600 °C gives rise to elimination of the RGO component, leading to the formation of sheetlike porous aggregates of RGO-free TiO 2 nanoparticles. The nanocomposites calcined at 500-700 °C display promising functionality as negative electrodes for lithium ion batteries. Among the present calcined derivatives, the 2D sheet-shaped aggregate of TiO 2 nanoparticles obtained from calcination at 600 °C delivers the greatest specific discharge capacity with good capacity retention for all current density conditions applied. Such superior electrode performance of the nanocomposite calcined at 600 °C is attributable both to the improved stability of the crystal structure and crystal morphology of titania and to the enhancement of Li + ion transport through the enlargement of mesopores. The present findings clearly demonstrate the usefulness of RGO nanosheets as a platform for 2D-ordered superstructures of metal oxide nanoparticles with improved electrode performance. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI 10.1002/chem.201200551
Citations Scopus - 28
2012 Kim IY, Lee JM, Kim TW, Kim HN, Kim HI, Choi W, Hwang SJ, 'A strong electronic coupling between graphene nanosheets and layered titanate nanoplates: A soft-chemical route to highly porous nanocomposites with improved photocatalytic activity', Small, 8 1038-1048 (2012)

Strongly coupled nanocomposites of layered titanate and reduced graphene oxide (RGO) are synthesized by electrostatically derived self-assembly between negatively charged RGO nano... [more]

Strongly coupled nanocomposites of layered titanate and reduced graphene oxide (RGO) are synthesized by electrostatically derived self-assembly between negatively charged RGO nanosheets and positively charged TiO 2 nanosols, which is then followed by a phase transition of the anatase TiO 2 component into layered titanate. The resulting nanocomposite consists of thin 2D nanoplates of lepidocrocite-type layered titanate immobilized on the surface of RGO nanosheets. The composite formation with RGO nanosheets is effective not only in promoting the phase transition of anatase TiO 2 nanosols, but also in improving the thermal stability of the layered titanate, indicating the role of RGO nanosheets as an agent for directing and stabilizing layered structures. The layered-titanate-RGO nanocomposites exhibit remarkably expanded surface area with the formation of micropores and mesopores. The composite formation with RGO nanosheets gives rise to the disappearance of the reflectance edge of layered titanate in the diffuse reflectance UV-vis spectra, indicating a strong electronic coupling between the RGO and layered titanate. The strong electronic correlation between the two components is further evidenced by the visible-light-induced generation of photocurrents after the hybridization with RGO. The layered-titanate-RGO nanocomposite shows a higher activity for the photodegradation of organic molecules than uncomposited layered titanate, underscoring the usefulness of graphene hybridization in improving the photocatalyst performance of layered titanate. The experimental findings presented here clearly demonstrate that the self-assembly of metal oxide nanoparticles with RGO 2D nanosheets is quite effective not only in synthesizing porous metal-oxide-graphene nanocomposites with improved photo-induced functionality, but also in achieving strong electronic coupling between RGO and metal oxides. Strongly coupled nanocomposites of layered titanate and reduced graphene oxide (RGO) are synthesized by self-assembly involving RGO nanosheets and TiO 2 nanosols and the following phase transformation of titania. A strong electronic coupling between the two nanospecies remarkably enhances visible light absorption. The hybridization with RGO improves the photocatalytic activity of the layered titanate for the visible-induced generation of photocurrent and the photodegradation of organic molecules. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI 10.1002/smll.201101703
Citations Scopus - 94
2012 Han SY, Kim IY, Jo KY, Hwang SJ, 'Solvothermal-assisted hybridization between reduced graphene oxide and lithium metal oxides: A facile route to graphene-based composite materials', Journal of Physical Chemistry C, 116 7269-7279 (2012)

Hybridization between lithium metal oxide and reduced graphene oxide, or RGO, can be achieved by the solvothermal treatment of the water/ethanol-based suspension of graphite oxide... [more]

Hybridization between lithium metal oxide and reduced graphene oxide, or RGO, can be achieved by the solvothermal treatment of the water/ethanol-based suspension of graphite oxide, or GO, nanosheets containing powdery lithium metal oxide. The solvothermal treatment for the mixture suspension of GO and Li 4Ti 5O 12 gives rise not only to the reduction of GO to RGO but also to the attachment of the Li 4Ti 5O 12 particles to the flat surface of RGO 2D nanosheets. The crystal structure and crystal morphology of the Li 4Ti 5O 12 particles remain intact after the composite formation with the RGO nanosheets. The formation of chemical bonds and internal electron transfer between the RGO and Li 4Ti 5O 12 components is evidenced by micro-Raman and X-ray photoelectron spectroscopy, showing the weakening of the carbon-carbon bonds and the formation of carbon-oxygen bonds. In comparison with the pristine Li 4Ti 5O 12 material, the Li 4Ti 5O 12-RGO nanocomposites display better anode performance with a larger discharge capacity of ~175 mAhg -1, underscoring the merit of RGO hybridization in improving the electrode performance of bulk metal oxide. Diffuse reflectance UV-vis and photoluminescence spectroscopic analyses reveal a strong electrical connection between lithium titanate and RGO, which is mainly responsible for the observed improvement of the electrode performance upon the composite formation. In addition to the electrode performance, the photocatalytic activity of the lithium titanate for the generation of photocurrent can be remarkably enhanced by the coupling with RGO, confirming the usefulness of the present synthetic method in optimizing the photoinduced functionality of metal oxides. The solvothermal strategy presented here is also applicable for the synthesis of LiMn 2O 4-RGO nanocomposite showing much superior electrode performance over the pristine LiMn 2O 4. The experimental findings underscore that the present synthetic method can provide a universal way to not only immobilize multicomponent metal oxides on the surface of RGO nanosheets with a strong electrical connection but also improve the electrode and photocatalytic activity of these metal oxides. © 2012 American Chemical Society.

DOI 10.1021/jp301508k
Citations Scopus - 42
2012 Lee KM, Lee YR, Kim IY, Kim TW, Han SY, Hwang SJ, 'Heterolayered Li

Novel heterolayered nanocomposites consisting of interstratified MnO 2 and [Mn 1/3 Co 1/3 Ni 1/3 ]O 2 nanosheets are synthesized by a layer-by-layer self-assembly between negative... [more]

Novel heterolayered nanocomposites consisting of interstratified MnO 2 and [Mn 1/3 Co 1/3 Ni 1/3 ]O 2 nanosheets are synthesized by a layer-by-layer self-assembly between negatively charged metal oxide nanosheets and lithium cations. According to powder X-ray diffraction and micro-Raman analysis, all of the as-prepared Li + -xMnO 2 -(1-x)[Mn 1/3 Co 1/3 Ni 1/3 ]O 2 nanocomposites with x = 1, 0.7, and 0.4 have a lamella structure with similar basal spacing of ~ 7.1 Å, indicating the formation of lithium intercalation structure with cointercalated water bilayers. The nanoscale mixing of MnO 2 and [Mn 1/3 Co 1/3 Ni 1/3 ]O 2 nanosheets is confirmed by energy-dispersive spectrometry-elemental mapping analysis. Upon a self-assembly with Li + ions, there occur no marked changes in the octahedral symmetry and mixed oxidation state of M 3+ /M 4+ ions (M = Mn, Co, and Ni) in the precursor metal oxide nanosheets. All of the as-prepared nanocomposites commonly experience a structural transformation from hydrated layered structure to dehydrated layered structure at 200 °C, which is followed by the second-phase transition to cubic spinel structure at 600 °C. Despite distinct structural changes of the nanocomposites at elevated temperatures, their porous stacking structure is well-maintained up to 400 °C. The heat-treatment at 400 °C leads to a significant improvement of the discharge capacity of the present nanocomposites because of the dehydration of as-prepared materials and the enhancement of crystallinity. The doping of [Mn 1/3 Co 1/3 Ni 1/3 ]O 2 layers enables us not only to increase the discharge capacity of the Li-MnO 2 nanocomposite but also to prevent the phase transition of layered manganese oxide to spinel structure during electrochemical cycling. The present study clearly demonstrates that a postcalcination process as well as a partial doping of [Mn 1/3 Co 1/3 Ni 1/3 ]O 2 layer is effective in improving the electrode performance of reassembled Li-MnO 2 nanocomposites. © 2012 American Chemical Society.

DOI 10.1021/jp210063c
Citations Scopus - 17
2011 Gunjakar JL, Kim TW, Kim HN, Kim IY, Hwang SJ, 'Mesoporous layer-by-layer ordered nanohybrids of layered double hydroxide and layered metal oxide: Highly active visible light photocatalysts with improved chemical stability', Journal of the American Chemical Society, 133 14998-15007 (2011)

Mesoporous layer-by-layer ordered nanohybrids highly active for visible light-induced O 2 generation are synthesized by self-assembly between oppositely charged 2D nanosheets of Z... [more]

Mesoporous layer-by-layer ordered nanohybrids highly active for visible light-induced O 2 generation are synthesized by self-assembly between oppositely charged 2D nanosheets of Zn-Cr-layered double hydroxide (Zn-Cr-LDH) and layered titanium oxide. The layer-by-layer ordering of two kinds of 2D nanosheets is evidenced by powder X-ray diffraction and cross-sectional high resolution-transmission electron microscopy. Upon the interstratification process, the original in-plane atomic arrangements and electronic structures of the component nanosheets remain intact. The obtained heterolayered nanohybrids show a strong absorption of visible light and a remarkably depressed photoluminescence signal, indicating an effective electronic coupling between the two component nanosheets. The self-assembly between 2D inorganic nanosheets leads to the formation of highly porous stacking structure, whose porosity is controllable by changing the ratio of layered titanate/Zn-Cr-LDH. The resultant heterolayered nanohybrids are fairly active for visible light-induced O 2 generation with a rate of ~1.18 mmol h -1 g -1 , which is higher than the O 2 production rate (~0.67 mmol h -1 g -1 ) by the pristine Zn-Cr-LDH material, that is, one of the most effective visible light photocatalysts for O 2 production, under the same experimental condition. This result highlights an excellent functionality of the Zn-Cr-LDH-layered titanate nanohybrids as efficient visible light active photocatalysts. Of prime interest is that the chemical stability of the Zn-Cr-LDH is significantly improved upon the hybridization, a result of the protection of the LDH lattice by highly stable titanate layer. The present findings clearly demonstrate that the layer-by-layer-ordered assembly between inorganic 2D nanosheets is quite effective not only in improving the photocatalytic activity of the component semiconductors but also in synthesizing novel porous LDH-based hybrid materials with improved chemical stability. © 2011 American Chemical Society.

DOI 10.1021/ja203388r
Citations Scopus - 310
2011 Woo MA, Kim TW, Kim IY, Hwang SJ, 'Synthesis and lithium electrode application of ZnO-ZnFe

The mixed metal oxide nanocomposites composed of spinel ZnFe 2O4 and wurzite ZnO phases are prepared by the heat-treatment for Zn,Fe-layered double hydroxide (Zn,Fe-LDH) at elevat... [more]

The mixed metal oxide nanocomposites composed of spinel ZnFe 2O4 and wurzite ZnO phases are prepared by the heat-treatment for Zn,Fe-layered double hydroxide (Zn,Fe-LDH) at elevated temperatures. The following selective etching of ZnO domains from the nanocomposites yields porously assembled ZnFe2O4 nanocrystals. The structural transformation from the brucite LDH structure to the spinel and/or wurzite structures was confirmed by X-ray diffraction and X-ray absorption spectroscopy. According to chemical analysis, electron microscopy, and N2 adsorption-desorption isotherm measurements, not only the chemical composition of the nanocomposites but also the particle size and surface area of the etched ZnFe2O4 nanoparticles can be controlled by changing the Fe/Zn ratio in the precursor metal hydroxide. The calcined nanocomposites show promising functionality as negative electrode materials for lithium ion batteries, which is superior to that of uncomposited ZnFe2O4 or ZnO phase. The degrading of the electrode performance of the nanocomposites after the selective etching of ZnO component clearly demonstrates the positive effect of nanocomposite formation on the electrochemical activity of metal oxides. © 2010 Elsevier B.V.

DOI 10.1016/j.ssi.2010.10.025
Citations Scopus - 41
2011 Kim IY, Lee KY, Kim TW, Hwang SJ, 'Porous zirconium complex-layered titanate nanohybrids with gas adsorption and photocatalytic activity', Materials Letters, 65 894-896 (2011)

Porous zirconium complex-layered titanate nanohybrids were synthesized by reassembling reaction between negative-charged layered titanate nanosheets and positive-charged zirconium... [more]

Porous zirconium complex-layered titanate nanohybrids were synthesized by reassembling reaction between negative-charged layered titanate nanosheets and positive-charged zirconium complex. According to powder X-ray diffraction and electron microscopy, titanate monolayers were interstratified with zirconium species with the repeating unit of ~ 1.2 nm. X-ray absorption spectroscopy at Zr K-edge and Ti K-edge clearly demonstrated that mononuclear zirconium complex was intercalated into lepidocrocite-structured titanate layers. From N 2 adsorption-desorption isotherm measurement, the hybridization reaction produced highly porous material with the expanded surface area of ~ 176 m2g- 1. The zirconium complex-layered titanate nanohybrids showed functionalities not only for adsorption of CO2 gas but also for photodegradation of organic molecules. This finding underscored that the reassembling of layered metal oxide with zirconium ions provides powerful ways to synthesize highly porous materials applicable for gas adsorbents and photocatalysts. © 2010 Elsevier B.V. All rights reserved.

DOI 10.1016/j.matlet.2010.12.002
Citations Scopus - 9
2011 Lee KM, Song MS, Kim IY, Kim TW, Hwang SJ, 'Effects of polyelectrolyte hybridization on the crystal structure, physicochemical properties, and electrochemical activity of layered manganese oxide', Materials Chemistry and Physics, 127 271-277 (2011)

The effects of polyelectrolyte intercalation on the crystal structure, physicochemical properties, and electrode performance of manganese oxide were investigated with intercalativ... [more]

The effects of polyelectrolyte intercalation on the crystal structure, physicochemical properties, and electrode performance of manganese oxide were investigated with intercalative nanohybrids composed of layered manganate nanosheets and polyelectrolytes such as polyethylenimine (PEI), poly(allylamine hydrochloride) (PAH), and poly(diallyldimethyl ammonium) chloride (PDDA). The intercalative hybridization between layered manganate nanosheets and polyelectrolytes was confirmed by X-ray diffraction, field emission-scanning electron microscopy, and FT-IR spectroscopy. N2 adsorption-desorption isotherm analysis clearly demonstrated that the PEI-layered MnO2 nanohybrid showed a larger surface area than the other nanohybrids. According to Mn K-edge X-ray absorption spectroscopy, the PEI-layered MnO2 nanohybrid possessed a lower Mn oxidation state compared with the other nanohybrids, reflecting the electron transfer from Lewis basic amine groups of the PEI to the manganate layers. All the present nanohybrids exhibited pseudocapacitance behavior, suggesting their applicability as electrode for supercapacitor. The PEI-layered MnO2 nanohybrid showed larger capacitances than the PDDA- and PAH-intercalates. The observed superior electrode performance of the former could be understood by a larger surface area and a lower Mn oxidation state of this material. © 2011 Elsevier B.V. All rights reserved.

DOI 10.1016/j.matchemphys.2011.02.002
Citations Scopus - 7
2011 Kim HN, Kim TW, Choi KH, Kim IY, Kim YR, Hwang SJ, 'Self-assembly of nanosized 0D clusters: CdS quantum dot-polyoxotungstate nanohybrids with strongly coupled electronic structures and visible-light-active photofunctions', Chemistry - A European Journal, 17 9626-9633 (2011)

Nanohybrids of CdS-polyoxotungstate with strongly coupled electronic structures and visible-light-active photofunctions can be synthesized by electrostatically derived self-assemb... [more]

Nanohybrids of CdS-polyoxotungstate with strongly coupled electronic structures and visible-light-active photofunctions can be synthesized by electrostatically derived self-assembly of very small CdS quantum dots, or QDs, (particle size ¿ 2.5 nm) and polyoxotungstate nanoclusters (cluster size ¿ 1 nm). The formation of CdS-polyoxotungstate nanohybrids is confirmed by high-resolution transmission electron microscopy, elemental mapping, and powder X-ray diffraction analysis. Due to the strong electronic coupling between two semiconductors, the CdS-polyoxotungstate nanohybrids show a narrow bandgap energy of around 1.9-2.7 eV, thus reflecting their ability to harvest visible light. Time-resolved photoluminescence experiments indicate that the self-assembly between nanosized CdS and polyoxotungstate is very effective in increasing the lifetime of holes and electrons, thus indicating an efficient electron transfer between two-component semiconductors. The hybridization results not only in a significant improvement in the photostability of CdS QD but also in the creation of visible-light-induced photochromism. Of particular importance is that the present nanohybrids show visible-light-driven photocatalytic activity to produce H 2 and O 2, which is superior to those of the unhybridized CdS and polyoxotungstate. The self-assembly of nanometer-level semiconductor clusters can provide a powerful way of optimizing the photoinduced functionalities of each component (i.e., visible-induced photochromism and photocatalysis) by means of strong electronic coupling. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI 10.1002/chem.201100583
Citations Scopus - 22
2011 Woo MA, Song MS, Kim TW, Kim IY, Ju JY, Lee YS, et al., 'Mixed valence Zn-Co-layered double hydroxides and their exfoliated nanosheets with electrode functionality', Journal of Materials Chemistry, 21 4286-4292 (2011)

New phases of Zn-Co-layered double hydroxides (Zn-Co-LDHs) were synthesized for the first time via a co-precipitation reaction using hydrogen peroxide as an oxidant. According to ... [more]

New phases of Zn-Co-layered double hydroxides (Zn-Co-LDHs) were synthesized for the first time via a co-precipitation reaction using hydrogen peroxide as an oxidant. According to powder X-ray diffraction and field emission-scanning electron microscopy, both nitrate- and sulfate-forms of the Zn-Co-LDHs crystallized with the brucite-type layer structure having interlayer nitrate and sulfate anions, respectively, and commonly showed plate-like morphology with a crystal size of several hundred nanometers. dc magnetic susceptibility measurements revealed that the Zn-Co-LDHs displayed ferromagnetic/ antiferromagnetic transitions below 15 K and the magnetic moment calculated from the paramagnetic region (30-300 K) indicated the co-existence of weak field Co 2+ and strong field Co 3+ ions. The mixed oxidation state of Co 2+ /Co 3+ was confirmed by the results of iodometry and X-ray absorption near-edge structure spectroscopy. The heat-treatment for the Zn-Co-LDHs at elevated temperatures produced mixed metal oxide nanocomposites composed of spinel ZnCo 2 O 4 and wurzite ZnO phases. The colloidal suspension of exfoliated Zn-Co-LDH nanosheets could be synthesized by dispersion of the pristine LDH materials in formamide, which was confirmed by the Tyndall phenomenon, high resolution-transmission electron microscopy/selected area electron diffraction, and UV-vis spectroscopy. The Zn-Co-LDH film fabricated with the restacked nanosheets exhibited pseudocapacitive behavior with a large specific capacitance and a good capacitance retention. The present findings underscore that the newly synthesized mixed valence Zn-Co-LDH phases showed promising functionality as a supercapacitor electrode material and also showed interesting magnetic coupling behavior. © 2011 The Royal Society of Chemistry.

DOI 10.1039/c0jm03430d
Citations Scopus - 79
2011 Ha HW, Kim IY, Hwang SJ, Ruoff RS, 'One-pot synthesis of platinum nanoparticles embedded on reduced graphene oxide for oxygen reduction in methanol fuel cells', Electrochemical and Solid-State Letters, 14 (2011)

A simple approach has been developed for the synthesis of Pt nanoparticles with uniform diameters of approximately 2.9 nm supported on reduced graphene oxide (RG-O) platelets via ... [more]

A simple approach has been developed for the synthesis of Pt nanoparticles with uniform diameters of approximately 2.9 nm supported on reduced graphene oxide (RG-O) platelets via a modified polyol method. Compared to Johnson Matthey (JM) Pt/C (75 wt Pt) catalyst, the Pt/RG-O (70 wt Pt) composite showed much higher electrochemical surface area, greater catalytic activity towards the oxygen reduction reaction (ORR), and significantly better single cell polarization performance. The maximum power density of the Pt/RG-O composite was about 128 mW cm-2, an 11 greater than the JM Pt/C commercial catalyst. © 2011 The Electrochemical Society.

DOI 10.1149/1.3584092
Citations Scopus - 69
2011 Ko JE, Kim IY, Hwang SJ, Jung H, 'Study on the structural and photocatalytic properties for pore size tailored SnO

A new mesoporous SnO 2-pillared layered titanate is prepared by hybridizing the exfoliated titanate nanosheets with SnO 2 nanosol particles. The pore size tailored porous nanohybr... [more]

A new mesoporous SnO 2-pillared layered titanate is prepared by hybridizing the exfoliated titanate nanosheets with SnO 2 nanosol particles. The pore size tailored porous nanohybrids (S BET = 74~280 m 2/g and d = 18~96 Å) are obtained after calcining an as-prepared sample. The mesoporous nanohybrids exhibited different photocatalytic behaviors for salicylic acid and methylene blue depending upon their crystallinity and porous structure. Copyright © 2011 American Scientific Publishers All rights reserved.

DOI 10.1166/jnn.2011.3341
Citations Scopus - 4
2011 Kim TW, Yoo H, Kim IY, Ha HW, Han AR, Chang JS, et al., 'A composite formation route to well-crystalline manganese oxide nanocrystals: High catalytic activity of manganate-alumina nanocomposites', Advanced Functional Materials, 21 2301-2310 (2011)

Manganese oxide nanocrystals are combined with aluminum oxide nanocrystals to improve their crystallinity via calcination without a significant increase of crystal size. A nanocom... [more]

Manganese oxide nanocrystals are combined with aluminum oxide nanocrystals to improve their crystallinity via calcination without a significant increase of crystal size. A nanocomposite, consisting of two metal oxides, can be synthesized by the reaction between permanganate anions and aluminum oxyhydroxide keggin cations. The as-prepared manganese oxide-aluminum oxide nanocomposite is X-ray amorphous whereas heat-treatment gives rise to the crystallization of an a-MnO2 phase at 600 °C and Mn 3O4/Mn2O3 and ¿-Al 2O3 phases at 800 °C. Electron microscopy and N 2 adsorption-desorption-isotherm analysis clearly demonstrate that the as-prepared nanocomposite is composed of a porous assembly of monodisperse primary particles with a size of ~20 nm and a surface area of >410 m 2 g-1. Of particular interest is that the small particle size of the as-prepared nanocomposite is well-maintained up to 600 °C, a result of the prevention of the growth of manganate grains through nanoscale mixing with alumina grains. The calcined nanocomposite shows very-high catalytic activity for the oxidation of cyclohexene with an extremely high conversion efficiency of >95% within 15 min. The present results show that the improvement of the crystallinity without significant crystal growth is very crucial for optimizing the catalytic activity of manganese oxide nanocrystals. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI 10.1002/adfm.201100218
Citations Scopus - 13
2011 Kim HN, Kim TW, Kim IY, Hwang SJ, 'Cocatalyst-free photocatalysts for efficient visible-light-induced H

Highly efficient, visible-light-induced H2 generation can be achieved without the help of a Pt cocatalyst by new hybrid photocatalysts, in which CdS quantum dots (QDs) (particle s... [more]

Highly efficient, visible-light-induced H2 generation can be achieved without the help of a Pt cocatalyst by new hybrid photocatalysts, in which CdS quantum dots (QDs) (particle size ¿2.5 nm) are incorporated in the porous assembly of sub-nanometer-thick layered titanate nanosheets. Due to the very-limited crystal dimension of component semiconductors, the electronic structure of CdS QDs is strongly coupled with that of the layered titanate nanosheets, leading to an efficient electron transfer between them and the enhancement of the CdS photostability. As a consequence of the promoted electron transfer, the photoluminescence of CdS QDs is nearly quenched after hybridization, indicating the almost-suppression of electron-hole recombination. These Pt-cocatalyst-free, CdS-layered titanate nanohybrids show much-higher photocatalytic activity for H2 production than the precursor CdS QDs and layered titanate, which is due to the increased lifetime of the electrons and holes, the decrease of the bandgap energy, and the expansion of the surface area upon hybridization. The observed photocatalytic efficiency of these Pt-free hybrids (¿1.0 mmol g-1 h-1) is much greater than reported values of other Pt-free CdS-TiO2 systems. This finding highlights the validity of 2D semiconductor nanosheets as effective building blocks for exploring efficient visible-light-active photocatalysts for H 2 production. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI 10.1002/adfm.201100453
Citations Scopus - 156
2011 Jang JH, Kim J, Lee YH, Kim IY, Park MH, Yang CW, et al., 'One-pot synthesis of core-shell-like Pt

2-3 nm sized Pt 3 Co nanoparticles (NPs) with Pt-enriched shells on a carbon support were prepared by a one-step ultrasound polyol process on Pt(acac) 2 (acac = acetylacetonate) a... [more]

2-3 nm sized Pt 3 Co nanoparticles (NPs) with Pt-enriched shells on a carbon support were prepared by a one-step ultrasound polyol process on Pt(acac) 2 (acac = acetylacetonate) and Co(acac) 2 . The ultrasound facilitates the conversion of Co(acac) 2 and retards the conversion of Pt(acac) 2 into NPs, which can be explained with the different vapour pressures of the metal precursors. The Pt-enriched shell structure of the NPs by this method, as opposed to the alloy-like elemental distribution of the NPs synthesized in similar conditions but without ultrasound, was evidenced by transmission electron microscopy, magnetism data, extended X-ray absorption fine structure analyses, and chemical replacement tests of Co with Ru 3+ . Electrochemical oxygen reduction reaction data of these NPs showed improved performance from the commercial Pt/C with the NPs with Pt-enriched shells showing the highest activity. © The Royal Society of Chemistry 2011.

DOI 10.1039/c1ee01825f
Citations Scopus - 60
2011 Sung DY, Kim IY, Kim TW, Song MS, Hwang SJ, 'Room temperature synthesis routes to the 2D nanoplates and 1D nanowires/nanorods of manganese oxides with highly stable pseudocapacitance behaviors', Journal of Physical Chemistry C, 115 13171-13179 (2011)

The 2D nanoplates of d-MnO2 and the 1D nanowires/nanorods of a-MnO2 can be synthesized at room temperature via one-pot oxidation reaction of commercially available divalent mangan... [more]

The 2D nanoplates of d-MnO2 and the 1D nanowires/nanorods of a-MnO2 can be synthesized at room temperature via one-pot oxidation reaction of commercially available divalent manganese compounds. Treating the MnO or MnCO3 precursor with persulfate ions for 1-2 days yields layered d-MnO2 2D nanoplates, whereas the same oxidation reaction for the MnSO4 precursor produces ¿-MnO 2-structured 3D urchins. As the reaction time is extended for ~14-21 days, not only d-MnO2 nanoplates but also ¿-MnO2 urchins are changed to wellseparated 1D nanostructured a-MnO2 materials with controllable diameters. According to N2 adsorption-desorption isotherm measurements and Mn K-edge X-ray absorption spectroscopy, all the obtained manganate nanostructures show expanded surface areas of ~50-120 m2 g-1 and the mixed oxidation state of Mn3+/Mn4+, respectively. All the present nanostructured manganese oxides exhibit pseudocapacitance behaviors with large specific capacitance and excellent capacitance retention, highlighting their promising functionality as a supercapacitor electrode. Among the materials under investigation, the d-MnO2 2D nanoplates show the largest specific capacitance (~180-210 F g-1). The present finding clearly demonstrates that the room-temperature oxidation reaction of the MnO orMnCO3 precursor can provide a facile soft-chemical route to 2D d-MnO2 nanoplates and 1D R-MnO2 nanowires/nanorods with highly stable pseudocapacitance behaviors. © 2011 American Chemical Society.

DOI 10.1021/jp202041g
Citations Scopus - 56
2011 Lee Y-R, Song M-S, Lee K-M, Kim I-Y, Hwang S-J, 'Synthesis and Electrochemical Characterization of Reduced Graphene Oxide-Manganese Oxide Nanocomposites', Journal of Electrochemical Science and Technology, 2 1-7 (2011)
DOI 10.5229/jecst.2011.2.1.001
2010 Kim IY, Lee SH, Ha HW, Kim TW, Han YS, Kang JK, et al., 'Effects of synthesis temperature and precursor composition on the crystal structure, morphology, and electrode activity of 1D nanostructured manganese oxides', Journal of Power Sources, 195 6101-6107 (2010)

1D nanostructured manganese oxides are prepared by oxidation reaction of precursor LiMn 2-x Cr x O 4 microcrystals under hydrothermal condition. The crystal structure and morpholo... [more]

1D nanostructured manganese oxides are prepared by oxidation reaction of precursor LiMn 2-x Cr x O 4 microcrystals under hydrothermal condition. The crystal structure and morphology of the obtained manganese oxides are strongly dependent on the reaction condition and the chemical composition of the precursors. The a-MnO 2 nanowires are prepared by reaction at 120 °C, and their aspect ratios decrease with the Cr content in the precursor. Treating precursors with persulfate ions at 160-180 °C yields the ß-MnO 2 nanorods for the precursors LiMn 2-x Cr x O 4 with lower Cr content and the a-MnO 2 nanowires for the precursors with higher Cr content. The structure dependence of the products on the Cr content in the precursors is related to the high octahedral site stabilization energy of Cr 3+ ions and/or to the increase of Mn valence state upon Cr substitution. The increase of Cr content in the precursors degrades the electrode performance for the manganates prepared at 160 °C but improves electrode activity for those prepared at 180 °C. This observation can be explained by the structural variation and chromium substitution of the hydrothermally treated manganates. We conclude that the use of spinel LiMn 2-x Cr x O 4 as precursors provides an effective way to synthesize 1D nanostructured manganate with tailored crystal structure and morphology. © 2009 Elsevier B.V. All rights reserved.

DOI 10.1016/j.jpowsour.2009.11.053
Citations Scopus - 6
2010 Kim IY, Jeong B, Yoon MY, Kim J, 'Fabrication and electrochemical application of monolayers of well-ordered macroporous silica', Journal of Nanoscience and Nanotechnology, 10 158-162 (2010)

Highly ordered macroporous silica films with a monolayer thickness and regular array of spherical pores with diameters of about 305 nm are prepared using templates self-assembled ... [more]

Highly ordered macroporous silica films with a monolayer thickness and regular array of spherical pores with diameters of about 305 nm are prepared using templates self-assembled by polymethylmethacrylate (PMMA) spheres on solid surfaces by spin coating. The macropores are uniform in size and completely exposed on the bottom surface of the film after the PMMA spheres are etched out. Based on electrochemical experiments, the film allows for easy mass transport of Ru(bpy) 32+ to the ITO surface. Electrochemical detection of DNA hybridization was also carried out in model oligonucleotide hybrids immobilized on the macroporous silica film. Copyright © 2010 American Scientific Publishers. All rights reserved.

DOI 10.1166/jnn.2010.1510
Citations Scopus - 1
2010 Song MS, Lee KM, Lee YR, Kim IY, Kim TW, Gunjakar JL, Hwang SJ, 'Porously assembled 2D nanosheets of alkali metal manganese oxides with highly reversible pseudocapacitance behaviors', Journal of Physical Chemistry C, 114 22134-22140 (2010)

Porously assembled 2D nanosheets of alkali metal manganese oxides were synthesized via the flocculation of exfoliated MnO 2 nanosheets with alkali metal cations. According to X-ra... [more]

Porously assembled 2D nanosheets of alkali metal manganese oxides were synthesized via the flocculation of exfoliated MnO 2 nanosheets with alkali metal cations. According to X-ray diffraction and electron microscopic analyses, the MnO 2 nanosheets were porously restacked with alkali metal cations, resulting in the mesoporous assembly of lamellar crystallites with surface expansion (~ 50-70 m 2 g -1 ). Mn K-edge X-ray absorption spectroscopy clearly demonstrated that manganese ions in the reassembled materials were stabilized in octahedral symmetry with the mixed oxidation state of Mn3+/Mn4+. The present reassembled manganates showed large capacitances of ~140-160 F g -1 and excellent cyclability of ~93-99% up to the 1000th cycle. The electrochemical cycling did not induce notable frustration in the crystal structure of manganate nanosheets, underscoring the high structural stability of the reassembled manganates. This study provided strong evidence for the effectiveness of the exfoliation- reassembling method in enhancing the capacitance performance of layered metal oxides. © 2010 American Chemical Society.

DOI 10.1021/jp108969s
Citations Scopus - 67
2009 Kim J, Kim IY, Choi MS, Wu Q, 'Label-free electrochemical detection of adenosine based on electron transfer from guanine bases in an adenosine-sensitive aptamer', Chemical Communications, 4747-4749 (2009)

The selective recognition of adenosine with an adenosine-sensitive oligonucleotide is studied via the electrochemical oxidation of guanine bases of the aptamer in solution, leadin... [more]

The selective recognition of adenosine with an adenosine-sensitive oligonucleotide is studied via the electrochemical oxidation of guanine bases of the aptamer in solution, leading to a label-free voltammetric aptasensor based on the difference in the oxidative electron transfer rate. © The Royal Society of Chemistry 2009.

DOI 10.1039/b908344h
Citations Scopus - 18
2009 Baek JY, Ha HW, Kim IY, Hwang SJ, 'Hierarchically assembled 2D nanoplates and 0d nanoparticles of lithium-rich layered lithium manganates applicable to lithium ion batteries', Journal of Physical Chemistry C, 113 17392-17398 (2009)

The porous hierarchical assembly of lithium-rich Li1+xMnO 3-d 2D nanoplates as well as isolated 0D nanocrystalline homologues has been synthesized via lithiation reactions of nano... [more]

The porous hierarchical assembly of lithium-rich Li1+xMnO 3-d 2D nanoplates as well as isolated 0D nanocrystalline homologues has been synthesized via lithiation reactions of nanostructured manganese oxides under hydrothermal conditions. According to powder X-ray diffraction and electron microscopy, a hydrothermal LiOH treatment for nanostructured d-MnO2 precursor produces a lithium-rich Li 1+xMnO3-d phase with the nanoworm-like hierarchically assembled 2D nanoplate morphology. After the lithiation reaction under identical conditions, the 1D nanowires of the a-MnO2 precursor are transformed into the 0D nanoparticles of the Li 1+xMnO3-d phase. The Mn K-edge X-ray absorption spectroscopic analysis for the lithiated materials clearly demonstrated that tetravalent manganese ions are stabilized in octahedral sites of a Li 2MnO3-type layered structure composed of edge-shared MnO6/LiO6 octahedra. From electrochemical measurements, it was found that the lithiated Li1+xMnO3-d nanostructured materials show much superior electrode performance over the precursor manganese oxides and bulk lithium-rich manganate. The powder X-ray diffraction analyses for the electrochemically cycled derivatives clearly demonstrated that the improvement of electrode performance after lithiation can be attributed to the phase transformation to the Li-rich Li 1+xMnO3-d phase with high structural stability. On the basis of the present experimental findings, we are able to conclude that the present phase transformation route provides a new method not only to synthesize nanostructured lithium-rich manganese oxides with controllable dimensionality and morphology but also to improve the electrode performance of nanostructured manganese oxides. © 2009 American Chemical Society.

DOI 10.1021/jp904072r
Citations Scopus - 40
2009 Kim IY, Ha HW, Kim TW, Paik Y, Choy JH, Hwang SJ, 'Origin of improved electrochemical activity of ß-MnO

1D nanorods/nanowires of manganese oxides with different crystal structures and morphologies were prepared and characterized to understand the influence of the Mn valence in the s... [more]

1D nanorods/nanowires of manganese oxides with different crystal structures and morphologies were prepared and characterized to understand the influence of the Mn valence in the solid-state precursor on the electrochemical activity of these nanomaterials and to elucidate the mechanism responsible for the excellent activity of ß-MnO 2 nanorods as well. According to powder X-ray diffraction analyses, treating manganese oxide precursors that have an oxidation state of =+3 with persulfate ions under hydrothermal conditions yields manganese oxides with the ß-MnO 2 structure. In contrast, the use of a LiMn 2 O 4 precursor with a higher Mn valence leads to the formation of the a-MnO 2 -structured manganese oxide. Electron microscopic studies clearly show a 1D nanorod-type morphology for the ß-MnO 2 material, whereas a 1D nanowire-type morphology with a higher aspect ratio is observed for the a-MnO 2 material. The diameter of the ß-MnO 2 nanorods decreases as the Mn valence in the precursors becomes smaller. According to electrochemical measurements, the formation of nanorods dramatically improves the electrode performance of the ß-MnO 2 phase. This compares with a relatively weak performance enhancement for the a- and d-MnO 2 phases upon the nanowire formation. The optimum electrode property results from the smaller ß-MnO 2 nanorods prepared with the MnO precursor. 7 Li magic angle spinning nuclear magnetic resonance spectroscopy clearly demonstrates that Li + ions in the lithiated ß-MnO 2 phase are adsorbed mainly on the sample surface. On the basis of this finding, we attribute the improved electrode performance of the ß-MnO 2 nanorods to their expanded surface area. © 2009 American Chemical Society.

DOI 10.1021/jp908556h
Citations Scopus - 21
2009 Kim TW, Kim IY, Im JH, Ha H-W, Hwang S-J, 'Improved photocatalytic activity and adsorption ability of mesoporous potassium-intercalated layered titanate', Journal of Photochemistry and Photobiology A: Chemistry, 205 173-178 (2009)
DOI 10.1016/j.jphotochem.2009.04.025
2008 'Influence of Crystal Structure on the Chemical Bonding Nature and Photocatalytic Activity of Hexagonal and Cubic Perovskite Compounds', Bulletin of the Korean Chemical Society, 29 817-821 (2008)
DOI 10.5012/bkcs.2008.29.4.817
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20181 grants / $16,111

DVC(RI) Research Support for DECRA (DE18)$16,111

Funding body: University of Newcastle

Funding body University of Newcastle
Project Team Doctor Inyoung Kim
Scheme DECRA Support
Role Lead
Funding Start 2018
Funding Finish 2020
GNo G1801056
Type Of Funding Internal
Category INTE
UON Y

20172 grants / $332,625

Development of 2D inorganic nanostructures for hydrogen evolution reaction$307,823

Funding body: ARC (Australian Research Council)

Funding body ARC (Australian Research Council)
Project Team Doctor Inyoung Kim, Doctor Inyoung Kim
Scheme Discovery Early Career Researcher Award (DECRA)
Role Lead
Funding Start 2017
Funding Finish 2019
GNo G1701425
Type Of Funding Aust Competitive - Commonwealth
Category 1CS
UON Y

Research Support for DECRA$24,802

Funding body: The University of South Australia

Funding body The University of South Australia
Scheme DECRA Support
Role Lead
Funding Start 2017
Funding Finish 2017
GNo
Type Of Funding External
Category EXTE
UON N

20161 grants / $6,350

Australian Synchrotron$6,350

Funding body: Australian Synchrotron

Funding body Australian Synchrotron
Scheme Travel Grant
Role Lead
Funding Start 2016
Funding Finish 2018
GNo
Type Of Funding External
Category EXTE
UON N
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Research Supervision

Number of supervisions

Completed1
Current5

Current Supervision

Commenced Level of Study Research Title Program Supervisor Type
2019 PhD Porous Carbon Nitride Nanodots: Towards Electrochemical Energy Storage and Conversion Devices PhD (Engineering), Faculty of Engineering and Built Environment, The University of Newcastle Principal Supervisor
2019 PhD Halloysite Derived Nanoporous Carbon Nitride Nanosheets for Catalytic Applications PhD (Chemical Engineering), Faculty of Engineering and Built Environment, The University of Newcastle Co-Supervisor
2019 PhD Electrical Stimulation Properties of Carbon Nanotubes (SWNT and MWNT) for Enhanced Delivery of Wound Healing Agents PhD (Engineering), Faculty of Engineering and Built Environment, The University of Newcastle Principal Supervisor
2018 PhD Design, Synthesis and Properties of Nanoporous Chalcogenide materials with Multiple Dopants PhD (Engineering), Faculty of Engineering and Built Environment, The University of Newcastle Co-Supervisor
2018 PhD Synthesis N-doped Nanoporous Carbon with Different Metal or Metal Oxide Nanoparticles and their Applications in Dehydrogenation of Organic Hydrides PhD (Engineering), Faculty of Engineering and Built Environment, The University of Newcastle Co-Supervisor

Past Supervision

Year Level of Study Research Title Program Supervisor Type
2018 PhD Biomass derived porous carbon for CO2 capture Chemical Engineering, The University of South Australia Co-Supervisor
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Research Collaborations

The map is a representation of a researchers co-authorship with collaborators across the globe. The map displays the number of publications against a country, where there is at least one co-author based in that country. Data is sourced from the University of Newcastle research publication management system (NURO) and may not fully represent the authors complete body of work.

Country Count of Publications
Korea, Republic of 69
Australia 8
India 4
United States 4
Germany 2
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Dr Inyoung Kim

Position

ARC Decra Fellow
Global Innovative Center for Advanced Nanomaterials (GICAN)
School of Engineering
Faculty of Engineering and Built Environment

Contact Details

Email inyoung.kim@newcastle.edu.au
Phone (02) 4921 8932
Mobile 0450615169

Office

Room ATC 220
Building ATC Building
Location Callaghan
University Drive
Callaghan, NSW 2308
Australia
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