Dr Jae-Hun Yang

Transition metal carbides, known as MXenes, particularly Ti3C2Tx, have been extensively explored as promising materials for electrochemical reactions. However, transition metal carbonitride MXenes with high nitrogen content for electrochemical reactions are rarely reported. In this work, transition metal carbonitride MXenes incorporated with Pt-based electrocatalysts, ranging from single atoms to sub-nanometer dimensions, are explored for hydrogen evolution reaction (HER). The fabricated Pt clusters/MXene catalyst exhibits superior HER performance compared to the single-atom-incorporated MXene and commercial Pt/C catalyst in both acidic and alkaline electrolytes. The optimized sample shows low overpotentials of 28, 65, and 154¿mV at a current densities of 10, 100, and 500¿mA¿cm-2, a small Tafel slope of 29¿mV dec-1, a high mass activity of 1203¿mA mgPt-1 and an excellent turnover frequency of 6.1¿s-1 in the acidic electrolyte. Density functional theory calculations indicate that this high performance can be attributed to the enhanced active sites, increased surface functional groups, faster charge transfer dynamics, and stronger electronic interaction between Pt and MXene, resulting in optimized hydrogen absorption/desorption toward better HER. This work demonstrates that MXenes with a high content of nitrogen may be promising candidates for various catalytic reactions by incorporating single atoms or clusters. (Figure presented.).

Mesoporous silica-based materials are currently being explored as a new type of bioscaffold for bone regeneration applications. Zinc(Zn)¿ion incorporation is shown to play an important role in promoting bone regeneration and also providing antimicrobial activity to the scaffold materials. In this work, the role of pore size, geometry, and ordered structure on the Zn loading and release performance of two different mesoporous silica, SBA-1 and SBA-15, are compared. Zn loading is varied from 2.5 to 10 wt% for both samples, and its effect on the antibacterial and osteogenic activity is evaluated. Zn loading up to 10 wt% has a negligible effect on the morphology and textural properties of the mesoporous silica samples. The inductively coupled plasma mass spectrometry (ICP-MS) analysis reveals that SBA-15 exhibits significantly higher Zn release in Luria-Bertani (LB) broth as compared to SBA-1 that is reflected in the higher antibacterial activity of SBA-15 against both gram-positive and gram-negative bacteria. Various assays show that 5 wt% Zn loading is sufficient to produce both bactericidal and inhibitory effects on bacterial cells. The 5 wt% Zn-loaded samples induce osteogenic differentiation ofavianized bone marow-derived stromal cells (TVA-BMSCs) though SBA-15 samples show better compatibility compared to SBA-1, suggesting that Zn incorporation can produce sufficient antibacterial effect and osteogenic differentiation of TVA-BMSCs.

We report on the catalytic activity of ordered mesoporous aluminosilicate, AlSBA-1 with 3D cage type porous structure, in the isopropylation of naphthalene (NP). The higher isopropylates: triisopropylnaphthalene (TriIPN) and tetraisopropylnaphthalene (TetIPN) isomers were formed over AlSBA-1 in addition to isopropylnaphthalene (IPN) and diisoprpylnaphthalene (DIPN) isomers. The higher isopropylates were started to form at 225 °C as primary products, which were produced by multi-step isopropylation from NP occurred during one stay on the catalytic site cooperated with the propene adsorbed neighbor acid sites. TriIPN isomers were composed of four isomers (1,3,7-. 1,3,5-, 1,3,6-, and 1,4,6-) formed from DIPN isomers. These formations of TriIPN isomers are controlled by the distribution of DIPN isomers. ß,ß-DIPN isomers lead to a,ß,ß-TriIPN isomers, and a,a-DIPN to a,a,ß-TriIPN, respectively. However, a,ß-DIPN isomers give both of a,a,ß- and a,ß,ß-TriIPN isomers depending on the reaction conditions. The distribution of TriIPN isomers is operated by their kinetic and thermodynamic properties. Bulky and unstable a,a,ß-TriIPN isomers (1,3,5- and 1,4,6-) were predominant at low temperatures, 175¿250 °C, and at low NP/Cat ratio at 250 °C, where the catalysis mainly proceeded under kinetic control. However, the formation of slim and stable a,ß,ß-TriIPN isomers (1,3,7- and 1,3,6-) increased with raising the temperatures, and was primary at 300 °C, where the catalysis occurred under thermodynamic control. From these results, it is concluded that the isopropylation of NP over AlSBA-1 occurs under kinetic and/or thermodynamically controls based on the reactivity of the reactants and the stability of the products, and no steric control concerns by mesopores.

The isopropylation of naphthalene (NP) was carried out over a BEA zeolite (BEA38; SiO2/Al2O3 = 38) focused on the selectivities for diisopropylnaphthalene (DIPN) and triisopropylnaphthalene (TriIPN) isomers. The isopropylation gave possible eight DIPN isomers including ß,ß- (2,6- and 2,7-), a,ß- (1,3-, 1,6-, and 1,7-), and a,a- (1,4- and 1,5-). The catalysis over BEA works two types of controls: kinetic control operates to form predominantly bulky and unstable a,a-DIPN at low temperatures, and thermodynamic controls work for the predominant formation of the slim and stable ß,ß-DIPN at high temperatures, although the intermediately bulky and stable a,ß-DIPN are the major products through both controls. The enhanced selectivities for ß,ß-DIPN were observed at the early stages of the catalysis in the range of 200-300 °C, which operate under new type of thermodynamic control over fresh catalyst through thermodynamically preferred transition states; however, they decreased with the increase in the selectivities for a,a- and a,ß-DIPN, and converged after prolonged reaction period. The isopropylation of DIPN isomers gives TriIPN isomers: unstable and bulky 1,3,5- and 1,4,6-TriIPN with a,a,ß-substitution, and stable and slim 1,3,7- and 1,3,6-TriIPN with a,ß,ß-substitution. The low temperatures favor the former isomers, whereas the selectivity for the latter isomers increases with increasing reaction temperature. These results indicate that TriIPN isomers principally form under kinetic control at low temperatures, and thermodynamic controls participate in the catalysis at high temperatures. The selectivities for TriIPN isomers kept constant during the reaction at all temperatures: 200, 250, and 300 °C. The catalysis occurs inside the BEA channels and allow even the formation of bulky 1,3,5- and 1,4,6-TriIPN; however, all isomers cannot be isomerized to the others in the channels and on the external surfaces. Severe coke-deposition occurred during the catalysis, particularly in the early stages; however, the catalyst is recovered by the calcination with a small change in catalytic activity.

The isopropylation of naphthalene (NP) over USY zeolite (FAU06, SiO2/Al2O3 = 6) gave all eight possible diisopropylnaphthalene (DIPN) isomers: ß,ß- (2,6- and 2,7-), a,ß- (1,3-, 1,6-, and 1,7-), and a,a- (1,4- and 1,5-). The catalyses were operated under kinetic and/or thermodynamic controls depending on the reaction temperatures since the cavities of FAU topology are wide enough to form all DIPN isomers. Enhanced selectivities for ß,ß-DIPN were observed at the early stages at 200°C, 250°C, and 300°C although the selectivities decreased with the increasing periods, accompanying the increase in a,a- and a,ß-DIPN. The enhancement occurred under new types of thermodynamic controls through thermodynamically preferred transition states to ß,ß-DIPN. Triisopropylnaphthalene (TriIPN) isomers were also formed in the isopropylation. Unstable a,a,ß-TriIPN (1,4,6- and 1,3,5-) was predominantly formed at lower temperatures, however, decreased with the increased of stable a,ß,ß-TriIPN (1,3,6- and 1,3,7-) at higher temperatures. The predominant formation of 1,4,6-TriIPN was also observed in the initial stages in the range of 200°C, 250°C, and 300°C, as reaction period was increased, while the selectivity for the isomer was decreased with concomitant increase in the selectivities for the other isomers. These changes of the selectivities operated under kinetic and/or thermodynamic controls. Large cavities of the zeolite allowed the formation of all TriIPN isomers without steric restriction.

Skin cancer has emerged as one of the leading types of cancers in the world, causing a high impact on the global burden of health and the economy. Basal cell and squamous cell carcinoma are the localized forms of skin cancer with a high prevalence and can be treated with a high success rate. However, melanoma, a rare type of skin cancer with a high mortality rate, can metastasize and invade other parts of the body. Various skin cancer treatment approaches have been developed and advanced from localized to systemic treatment over the years to improve the low success rate associated with skin cancer, especially metastatic melanoma. The systemic treatment of skin cancer is highly benefitted by drug delivery systems (DDS) designed to function with much higher specificity and lower side effects than the direct treatment with drugs. While many nanomaterials based DDS have been developed in the past few years to take advantage of the small size and high functionality of nanomaterials, silica-based nanomaterials have recently emerged as the flexible DDS with a high biocompatibility, good clearance, a high drug loading capacity, and versatility to attach several drugs and targeting agents to its surface. In this review, recent progress in the treatment of melanoma using silica-based nanomaterials and their hybrids is discussed, highlighting the versatility and potential of these emerging nanomaterials as the DDS for delivering various molecules, including drugs and immunotherapy agents, peptides, and radio- and photo-active agents. The review also introduces various therapies available for the treatment of melanoma, including surgery, chemotherapy, targeted therapy, phototherapy, and immunotherapy and discusses the improvement in these therapies based on silica-based DDS. The review also highlights the role of silica nanomaterials and their hybrids in delivering combination therapy and the advantages of silica nanohybrids over pure silica-based DDS. Finally, we summarize the present status of silica-based nanomaterials in melanoma treatment and the current challenges that have to be solved for the clinical translation of these materials as DDS.

In this investigation, a hybrid of metal sulfide and carbon nitride (CN) is synthesized by in-situ chemical conversion between metallic species and a single precursor of carbon, nitrogen and sulfur elements through a strong p-d conjugation approach. It is observed that the local chemical alteration in the vicinity of N atom in the CN template triggers the formation of a highly p-conjugated CN system and efficient p-d hybridization at heterointerface. This is accelerated by partial substitution of the Fe atom for Mn ions in the MnS phase which significantly enhances the battery performance, delivering 2031 mA h g-1 after 500 cycles with inverse capacity growth. Via systematic in-depth characterizations, it is found that the gradual increase of Li-ion diffusion coefficients and charge transfer kinetics for repeated cycling is ascribed to the highly dispersed and uniform particles that are confined within the CN template through a strong p-d hybridization.

Prostate cancer (PCa) is one of the most commonly diagnosed cancers and is the fifth common cause of cancer-related mortality in men. Current methods for PCa treatment are insufficient owing to the challenges related to the non-specificity, instability and side effects caused by the drugs and therapy agents. These drawbacks can be mitigated by the design of a suitable drug delivery system that can ensure targeted delivery and minimise side effects. Silica based nanoparticles (SBNPs) have emerged as one of the most versatile materials for drug delivery due to their tunable porosities, high surface area and tremendous capacity to load various sizes and chemistry of drugs. This review gives a brief overview of the diagnosis and current treatment strategies for PCa outlining their existing challenges. It critically analyzes the design, development and application of pure, modified and hybrid SBNPs based drug delivery systems in the treatment of PCa, their advantages and limitations.

An integrated photocatalyst was prepared and its photoelectrocatalytic behavior for solar energy conversion was investigated. To make an integrated photocatalyst for hydrogen evolution, Pt and CdS clusters were embedded in zeolite as a cocatalyst and a photocatalyst, respectively. Pt particles were embedded in zeolite Y by ion exchange reaction with Pt (NH3)42+ and activation and reduction processes were followed. CdS clusters in zeolite Y cages were prepared by ion exchange reaction with Cd2+ and sulfurization with Na2S in aqueous solution was followed. The existence of CdS clusters in the cavities of zeolite Y was detected by IR spectra. UV absorption edges of the samples prepared show blue shifts about 0.03-0.12 eV from the edge of bulk CdS, which is an indication of CdS clusters formed in zeolite Y. The pore structure of samples was analyzed by BET and Langmuir method. The solar energy conversion into hydrogen was investigated, where sodium tartrate solution was used as a hole scavenger. We could observe that 1 wt% Pt supported sample was the most effective photocatalyst for hydrogen evolution (62 µL/mg after 4 hour reaction).