Dr Warwick Belcher

Understanding doping in polymer semiconductors has important implications for the development of organic electronic devices. This study reports a detailed investigation of the doping of the poly(3-hexylthiophene) (P3HT)/Nafion bilayer interfaces commonly used in organic biosensors. A combination of UV-visible spectroscopy, dynamic secondary ion mass spectrometry (d-SIMS), dynamic mechanical thermal analysis, and electrical device characterization reveals that the doping of P3HT increases with annealing temperature, and this increase is associated with thermally activated interdiffusion of the P3HT and Nafion. First-principles modeling of d-SIMS depth profiling data demonstrates that the diffusivity coefficient is a strong function of the molar concentration, resulting in a discrete intermixed region at the P3HT/Nafion interface that grows with increasing annealing temperature. Correlating the electrical conductance measurements with the diffusion model provides a detailed model for the temperature-modulated doping that occurs in P3HT/Nafion bilayers. Point-of-care testing has created a market for low-cost sensor technology, with printed organic electronic sensors well positioned to meet this demand, and this article constitutes a detailed study of the doping mechanism underlying such future platforms for the development of sensing technologies based on organic semiconductors.

Sodium tungsten bronze (NaxWO3) is a promising alternative plasmonic material to nanoparticulate gold due to its strong plasmonic resonances in both the visible and near-infrared (NIR) regions. Additional benefits include its simple production either as a bulk or a nanoparticle material at a relatively low cost. In this work, plasmonic NaxWO3nanoparticles were introduced and mixed into the nanoparticulate zinc oxide electron transport layer of a water processed poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PC61BM) nanoparticle (NP) based organic photovoltaic device (NP-OPV). The power conversion efficiency of NP-OPV devices with NaxWO3NPs added was found to improve by around 35% compared to the control devices, attributed to improved light absorption, resulting in an enhanced short circuit current and fill factor.

This work investigated the photophysical pathways for light absorption, charge generation, and charge separation in donor-acceptor nanoparticle blends of poly(3-hexylthiophene) and indene-C60-bisadduct. Optical modeling combined with steady-state and time-resolved optoelectronic characterization revealed that the nanoparticle blends experience a photocurrent limited to 60% of a bulk solution mixture. This discrepancy resulted from imperfect free charge generation inside the nanoparticles. High-resolution transmission electron microscopy and chemically resolved X-ray mapping showed that enhanced miscibility of materials did improve the donor-acceptor blending at the center of the nanoparticles; however, a residual shell of almost pure donor still restricted energy generation from these nanoparticles.

The history of organic photovoltaics has been characterised by the complex interplay between fundamental research, large scale manufacture and commercialization activities. In addition, the field is highly interdisciplinary; ranging across physics, chemistry and engineering. This environment has resulted in a frontier character to the field, with researchers constantly expanding into new areas and confronting new challenges as the area has developed. This article seeks to chart the developments in organic photovoltaic research, with emphasis on the last two decades, to provide some historical context to current status of the field.

The phase segregation in P3HT:PCBM blend films has been investigated from an experimental and theoretical viewpoint. Optical microscopy, atomic force microscopy, scanning electron microscopy and X-ray diffraction show that thermal annealing of P3HT:PCBM blend films leads to the formation of PCBM aggregates. These aggregates are composed of dense randomly packed ~50 nm PCBM crystallites with an overall aggregate density of ~0.85 g cm-3. By applying the critical radius of nucleation for PCBM and the Stokes-Einstein equation for mobility of PCBM in a P3HT matrix, a model is developed which explains the formation of both crystallites and aggregates.

In order for OPV devices to transition from the laboratory to the industrial scale, accurate measurements of device operating stability and lifetime are crucial. This paper compares the degradation of ITO/PEDOT:PSS/P3HT:ICBA/Ca/Al and ITO/MoO3/P3HT:ICBA/Ca/Al devices using the three main ISOS standard testing protocols: (a) ISOS-D-1, (b) ISOS-O-1 and (c) ISOS-L-1. We show that: (1) ITO/MoO3/P3HT:ICBA/Ca/Al devices are more stable than their PEDOT counterparts under the ISOS-D-1 protocol, as has been reported previously. (2) Under the ISOS-O-1 protocol, unencapsulated MoO3 based devices are more stable than the equivalent PEDOT device but, when encapsulated, the degradation rates of the MoO3 and PEDOT devices are the same. (3) By contrast, when measured under the ISOS-L protocol, the MoO3 based devices are either equivalent to (unencapsulated devices) or, indeed, actually degrade faster (encapsulated devices) that their PEDOT counterparts. We demonstrate that these differences arise from the dominant degradation mode changing under the different protocols. As such, this paper highlights that the choice of testing protocol significantly influences the reported stability of OPV devices. In particular, the ISOS-D and ISOS-L protocols do not necessary reflect OPV device performance under actual operating conditions and thus stability measurements using these protocols should be treated with caution.

We demonstrate a pathway for fully roll-to-roll (R2R) prepared organic solar cells in a normal geometry with a R2R sputtered aluminium top electrode. Initial attempts utilizing a stack geometry without an electron transport layer (ETL) failed to obtain working devices. By applying aluminium zinc oxide (AZO) as an ETL, and optimizing the AZO thickness, working printed OPV devices with an efficiency of 0.58% were obtained. Further optimization of the donor:acceptor ratio in the active layer increased the efficiency to 0.90%. This work demonstrates that normal geometry organic solar cells using a metal top contact can be produced using large scale production techniques.

Here we report the application of a conjugated copolymer based on thiophene and quinoxaline units, namely poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1), to nanoparticle organic photovoltaics (NP-OPVs). TQ1 exhibits more desirable material properties for NP-OPV fabrication and operation, particularly a high glass transition temperature (Tg) and amorphous nature, compared to the commonly applied semicrystalline polymer poly(3-hexylthiophene) (P3HT). This study reports the optimisation of TQ1:PC71BM (phenyl C71 butyric acid methyl ester) NP-OPV device performance by the application of mild thermal annealing treatments in the range of the Tg (sub-Tg and post-Tg), both in the active layer drying stage and post-cathode deposition annealing stage of device fabrication, and an in-depth study of the effect of these treatments on nanoparticle film morphology. In addition, we report a type of morphological evolution in nanoparticle films for OPV active layers that has not previously been observed, that of PC71BM nano-pathway formation between dispersed PC71BM-rich nanoparticle cores, which have the benefit of making the bulk film more conducive to charge percolation and extraction.

Single layer graphene has been successfully grown via chemical vapour deposition (CVD) at low temperature by using chlorobenzene trapped in a PMMA polymer matrix as the carbon source. By varying the carbon source temperature, we are able to vary the dominant carbon source from just chlorobenzene to PMMA. Raman spectroscopy and atomic force microscopy (AFM) have been used to characterize the as-grown graphene layer, while scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been used to characterize film quality and growth dynamics. Lower source temperatures (corresponding to a chlorobenzene carbon source) result in high quality single layer graphene whereas higher source temperatures (PMMA carbon source) produce disordered multilayered graphene films. SEM imaging reveals that a preferential surface mediated edge growth mechanism for single layer graphene is observed as a function of growth time. This development offers a new methodology for graphene synthesis at low temperatures with implications for the development of printed graphene structures.

The potential for organic electronic technologies to produce low-cost energy at large scales is often cited as the most attractive feature of these materials. Such aspirations depend on the ability of materials to be printed from solution at high speeds across large areas using roll-to-roll (R2R) processing. However, progressing the technology from the laboratory environment into the industrial manufacturing arena is highly challenging. Closing the gap between exciting laboratory scale insights and the industrial scale potential requires a new focus on upscaling existing technology. Some recent progress in this area is discussed, concentrating on the need to pursue research across several different scales simultaneously in order to most effectively optimize large-scale fabrication efforts. These discussions are placed in the context of a design philosophy that combines printing, coating, and vacuum-based procedures. The challenges associated with selecting, and subsequently synthesizing, the optimal materials for device construction at large scales are considered. Case histories that highlight the unique challenges encountered during printing, coating, and sputtering at the R2R scale are presented. Developing testing and characterization procedures that can interrogate organic photovoltaic device (OPV) structures in real time is also discussed, and the opportunity for new tools to probe device photophysics is highlighted. The collection of innovative approaches to R2R fabrication challenges discussed here highlights the exciting progress toward efficient OPV modules becoming a commercial reality.

Sequential deposition of monolayers, composed of nanoparticles with varied donor-acceptor concentration ratios, has allowed the fabrication of organic photovoltaic (OPV) active layers with engineered vertical morphology. The performance of polymer-polymer poly(9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4-phenylenediamine):poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)] (PFB:F8BT) and polymer-fullerene poly(3-hexylthiophene):phenyl C61 butyric acid methyl ester (P3HT:PCBM) nanoparticulate (NP), graded nanoparticulate (GNP) and bulk heterojunction (BHJ) OPV devices have been studied. For both material systems the highest device VOC is observed for the graded structure. Furthermore, thermal treatments can be used to alleviate parasitic series resistance in the GNP devices, thus improving device JSC and efficiency. Overall, this work shows that the nanoparticle approach provides a new experimental lever for morphology control in OPV devices.

The kinetics and thermodynamics of PCBM phase segregation and aggregation in P3HT:PCBM blends has been studied. We develop a thermodynamic model for PCBM phase segregation in P3HT:PCBM blends which explains the formation of nanoscale crystallites which subsequently diffuse and coalesce into larger PCBM aggregates. We show that the formation of nanoscale crystallites during the film making process prevents spinodal decomposition of the P3HT:PCBM blends even at PCBM weight fractions above the spinodal decomposition boundary for the system. Finally, we demonstrate that the observed aggregate morphology can be understood in terms of a kinetic model based on the diffusional flux lines of PCBM crystallite which, in turn, govern the evolution of the macroscopic growth front.

The synthesis and performance of a cost-effective mixed fullerene at the 100+ g scale with a reaction yield of 85% is demonstrated. The cost to convert a fullerene such as C60 into the mixed acceptor blend is less than $1 g-1. The photovoltaic performance of the mixed acceptor is demonstrated in both small scale and roll-to-roll printed devices.

We investigate the suitability of four different inorganic materials (chromium oxide (CrOX), titanium oxide (TiOX), aluminium doped zinc oxide (AZO) and zinc oxide (ZnO)) as electrode transport layers in fully roll-to-roll (R2R) fabricated P3HT:ICxA organic solar cells. CrOX and TiOX were found to be unsuitable, as the CrOX devices did not exhibit rectifying behaviour while the TiOX devices did not withstand the annealing conditions. Of the last two ETLs, ZnO showed by far the most promise with devices demonstrating an average efficiency of 2.2%, which is the highest reported value for R2R devices in normal geometry, and a significantly extended lifetime compared with AZO devices under ISOS-L-2 conditions.

Near-field scanning optical lithography (NSOL) has been used to produce ordered structures of the semi-conducting polymer poly(p-phenylene vinylene) at sizes comparable to optical wavelengths. Structures on this scale are of interest for integrated optical devices. Here we study the effect of precursor film thickness upon the size and shape of lithographically produced features. We show that the discrepancies between the predicted and measured structures arise from two key factors: (1) the inherent change in the refractive index of the precursor polymer that occurs during lithography and (2) the considerable length of a precursor polymer relative to the characteristic NSOL feature dimension. Suggestions are made for the improvement of modelling accuracy.

Abstract Scanning transmission X-ray microscopy (STXM) compositional mapping has been used to probe the mesomorphology of nanoparticles (NPs) synthesized from two very different polymer:fullerene blends: poly(3-hexylthiophene) (P3HT): phenyl-C61-butyric acid methyl ester (PCBM) and poly[4,8-bis(2-ethylhexyloxy)benzo(1,2-b:4,5-b')dithiophene-alt-5, 6-bis(octyloxy)-4,7-di(thiophen-2-yl)(2,1,3-benzothiadiazole)-5,5'-diyl] (PSBTBT): PCBM. The STXM data shows that both blends form core-shell NP structures with similar shell compositions, but with different polymer:fullerene ratios in the core regions. P3HT:PCBM and PSBTBT:PCBM NP organic photovoltaic (OPV) devices have been fabricated and exhibit similar device efficiencies, despite the PSBTBT being a much higher performing low band gap material. By comparing the measured NP shell and core compositions with the optimized bulk hetero-junction (BHJ) compositions, we show that the relatively higher performance of the P3HT:PCBM NP device arises from the fact that its shell composition is much closer to the optimal BHJ value than that of the PSBTBT:PCBM NP device.

Traditional artist-in-science-residency schemes have tended to focus on artists using scientific tools and technology as a medium for their art. What kind and quality of work might occur, however, between scientists working on cutting-edge solar energy research and a visual artist (a sculptor) when they are integrated in a truly collaborative environment? Is it good for the art? Is it good for the science? The authors describe a new methodology for art-science interactions whereby they have integrated arts practice within a scientific environment. A critical aspect of the methodology for the residency was the development of an interaction framework that ensured that both artist and scientist had equal voice in discussions involving the art and science of the project within an environment of mutual respect. The integration led to the development of outcomes that would not have occurred otherwise.

The effect of device architecture upon the response of printable enzymatic glucose sensors based on poly(3-hexythiophene) (P3HT) organic thin film transistors is presented. The change in drain current is used as the basis for glucose detection and we show that significant improvements in drain current response time can be achieved by modifying the design of the sensor structure. In particular, we show that eliminating the dielectric layer and reducing the thickness of the active layer reduce the device response time considerably. The results are in good agreement with a diffusion based model of device operation, where an initial rapid dedoping process is followed by a slower doping of the P3HT layer from protons that are enzymatically generated by glucose oxidase (GOX) at the Nafion gate electrode. The fitted diffusion data are consistent with a P3HT doping region that is close to the source-drain electrodes rather than located at the P3HT:[Nafion:GOX] interface. Finally, we demonstrate that further improvements in sensor structure and morphology can be achieved by inkjet-printing the GOX layer, offering a pathway to low-cost printed biosensors for the detection of glucose in saliva.

The diffusion of PCBM in P3HT:PCBM blend films has been investigated using multi-wavelength scanning absorption microscopy (MWSAM). By studying the depletion of PCBM in the vicinity of the phase segregated PCBM-rich regions that form upon thermal annealing, we are able to measure the diffusion constant and activation energy for PCBM diffusion in P3HT:PCBM blend films. The measured kinetic parameters are consistent with the diffusion of nanoscale PCBM crystallites rather than molecular PCBM. We show that the presence of two distinct diffusion processes in these blend materials provides an explanation for the large differences that have been reported for PCBM diffusion in P3HT:PCBM blends. This insight allows us to develop a unified model for PCBM mass transport in these materials.

Here, we report the development of an organic thin film transistor (OTFT) based on printable solution processed polymers and employing a quantum tunnelling composite material as a sensor to convert the pressure wave output from detonation transmission tubing (shock tube) into an inherently amplified electronic signal for explosives initiation. The organic electronic detector allows detection of the signal in a low voltage operating range, an essential feature for sites employing live ordinances that is not provided by conventional electronic devices. We show that a 30-fold change in detector response is possible using the presented detector assembly. Degradation of the OTFT response with both time and repeated voltage scans was characterised, and device lifetime is shown to be consistent with the requirements for on-site printing and usage. The integration of a low cost organic electronic detector with inexpensive shock tube transmission fuse presents attractive avenues for the development of cheap and simple assemblies for precisely timed initiation of explosive chains.

The impact of a calcium interface layer in combination with a thermal annealing treatment on the performance of poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C61-buteric acid methylester (PCBM) nanoparticle photovoltaic devices is investigated. Annealing is found to disrupt the microstructure of the nanoparticle active layer leading to a reduction in fill factor. However, X-ray photoelectron spectroscopy measurements show that the calcium interface layer causes PCBM to preferentially migrate to the cathode interface upon annealing, resulting in better charge extraction from the PCBM moiety, an increase in the built-in voltage, open-circuit voltage, and power conversion efficiency. Moreover, the annealing trends could be completely explained by the observed PCBM migration. Unlike P3HT:PCBM bulk heterojunction devices, the P3HT:PCBM nanoparticle devices showed a remarkable thermal stability up to 120°C. As such, OPVs fabricated from aqueous nanoparticle inks provide an attractive alternative to conventional organic solvent based bulk heterojunction devices.

Nanoparticulate zinc oxide can be prepared at low temperatures from solution processable zinc acetylacetonate. The use of this material as a cathode interfacial layer in nanoparticulate organic photovoltaic devices results in comparable performances to those based on reactive calcium layers. Importantly, the enhanced degradation stability and full solution processability make zinc oxide a more desirable material for the fabrication of large area printed devices. © 2014 AIP Publishing LLC.

We present a dynamic Monte Carlo (DMC) study of s-shaped current-voltage (I-V) behaviour in organic solar cells. This anomalous behaviour causes a substantial decrease in fill factor and thus power conversion efficiency. We show that this s-shaped behaviour is induced by charge traps that are located at the electrode interface rather than in the bulk of the active layer, and that the anomaly becomes more pronounced with increasing trap depth or density. Furthermore, the s-shape anomaly is correlated with interface recombination, but not bulk recombination, thus highlighting the importance of controlling the electrode interface. While thermal annealing is known to remove the s-shape anomaly, the reason has been not clear, since these treatments induce multiple simultaneous changes to the organic solar cell structure. The DMC modelling indicates that it is the removal of aluminium clusters at the electrode, which act as charge traps, that removes the anomalous I-V behaviour. Finally, this work shows that the s-shape becomes less pronounced with increasing electron-hole recombination rate; suggesting that efficient organic photovoltaic material systems are more susceptible to these electrode interface effects.

CE can efficiently separate poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonic acid) (PEDOT/PSS) complexes and free PSS in dispersions and can be used to estimate the degree of PSS doping. We investigated the doping efficiency of PSS on PEDOT in dispersions using CE and its effect on the conductivity of the resulting PEDOT/PSS films. Results of this study indicate that dispersions containing 1:2.5-3 EDOT:PSS feed ratio (by weight) exhibiting 72-73% PSS doping generate highly processable and highly conductive films. Conductivity can be optimized by limiting the time of reaction to 12 h. At this point of the reaction, the PEDOT/PSS segments, appearing as broad band in the electropherogram, could still exist in an extended coil conformation favoring charge transport resulting in high conductivity. Above a threshold PEDOT length formed at reaction times longer than 12 h, the PEDOT/PSS complex, appearing as spikes in the electropherogram, most likely have undergone a conformational change to coiled core-shell structure restricting charge transport resulting in low conductivity. The optimal conductivity (5.2 S/cm) of films from dispersions synthesized for 12 h is significantly higher than those from its commercial equivalent Clevios P and other reported values obtained under similar conditions without the addition of codopants. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Poly (3-hexylthiophene) (P3HT), at six molecular weights varying from 5 kDa to 72 kDa (Mw), was used to prepare P3HT: phenyl C61 butyric acid methyl ester (PCBM) nanoparticulate organic photovoltaic (NP OPV) devices and the effect of this variation on device performance is reported. Power conversion efficiency (PCE) is observed to peak for the mid-range of molecular weights tested, this behaviour varies from the trend generally observed with bulk heterojunction (BHJ) devices, where high molecular weight polymers deliver the highest PCEs. Here we demonstrate that polymer molecular weight affects the electronic, morphological and compositional structure of the nanoparticulate film. Significantly, it is the domain composition that is most highly correlated with device performance and this composition is driven by the PCBM mobility and aggregation within the nanoparticulate structure. © 2014 Elsevier B.V.

The preparation of two new tripodal 'pinwheel' type anion hosts based on a triethylbenzene core and bipyridinium or ethylnicotinium arms is reported. The new materials bind anions via CH¿anion interactions. Complexes with Br- and PF6- have been characterised by X-ray crystallography as both solvates in a pure form. In the bipyridinium host CH¿F interactions to PF6- induce a chiral C 3 symmetric conformation that is disrupted in the hydrate. The compound is also selective for ATP2- in aqueous acetonitrile. © The Royal Society of Chemistry 2006.

The synthesis, anion binding, and conformational properties of a series of 3-aminopyridinium-based, tripodal, tricationic hosts for anions are described. Slow anion and conformational exchange on the 1H NMR time scale at low temperature, coupled with NMR titration, results in a high level of understanding of the anion-binding properties of the compounds, particularly with respect to significant conformational change resulting from induced fit complexation. Peak selectivity for halides, particularly Cl-, is observed. The approach has been extended to dipodal and tripodal podands based on 3-aminopyridinium "arms" containing photoactive anthracenyl moieties. The 1,3,5-tripodal host shows a remarkable selectivity for acetate over other anions, in contrast to the analogous unsubstituted tris(3-aminopyridinium) analogue, despite the fact that low-temperature 1H NMR experiments reveal a total of four acetate-binding conformations. Photodimerization of anthracene units results in the formation of potential fluorescent anion sensors.

A simple but effective route has been developed to produce a series of molecular clefts, [(¿ 6 -p-cymene)RuCl (1) 2 ]PF 6 (4a),[(dppe)Pd(1) 2 ](BF 4 ) 2 (5a), [(dppe)Pd(2) 2 ](BF 4 ) 2 (5b), [(dppe)Pt (1) 2 ](BF 4 ) 2 (6a) and [(dppe)Pt(2) 2 ](BF 4 ) 2 (6b), that contain either a redox active ferrocenyl or a photoactive anthracenyl side arm, attached to a ruthenium(II), palladium(II) or platinum(II) backbone. Compounds 4a, 5a, 5b and 6a act as hosts for oxo-anions. Anion recognition is achieved via convergent hydrogen bond interactions from secondary amine functionality on the side arms. The binding is also enhanced by the positive charge of the metal centres. The X-ray crystal structure of the related [PdCl 2 (1) 2 ] (7) shows it to possess a trans geometry. The X-ray crystal structures of the monoadducts [(¿ 6 -p-cymene) RuCl 2 (1)] (3a) and [(¿ 6 -p-cymene)RuC l 2(2)] (3b), which show contrasting behaviour in their hydrogen bonding to coordinated chloride, are also reported. © 2002 Elsevier Science B.V. All rights reserved.

The solution-phase voltammetry of the modular podand, 1,3,5-tris(3-((ferrocenylmethyl)amino)pyridiniumyl)-2,4,6-triethylbenzene hexafluorophosphate, [PD][PF6]3, in acetonitrile (0.1 M Bu4NPF6) and the ionic liquids [1-butyl-3-methylimidazolium hexafluorophosphate, (ethylmethylimidazoliumyl)bis(trifluoromethylsulfonyl)-amide, and (n-butylmethylpyrrolidiniumyl)bis(trifluoromethylsulfonyl)amide] exhibits a well-defined diffusion-controlled process at a potential of about 1.40 V vs [Co(¿5-C5H5)2]+/0. Detailed chronoamperometric and near steady-state microdisk electrode studies reveal that although the process has many of the characteristics of a reversible one-electron oxidation reaction, it is actually a combination of three very closely spaced reversible one-electron processes, implying that there is minimal communication between the three ferrocenyl redox active centers present in the podand. The voltammetry of very slowly dissolving microparticles of [PD][PF6]3 mechanically attached to an electrode surface in contact with ionic liquids is indistinguishable from that observed when the podand is in the dissolved state in the ionic liquid. In contrast, cyclic voltammograms obtained when a [PD][PF6]3 modified electrode is in contact with aqueous electrolyte media exhibit behavior very different from that found in the solution phase. For example, in the presence of KPF6 electrolyte, three resolved oxidation peaks are detected, whereas in some other electrolyte media, transformations to features expected in stripping voltammetry are encountered on repetitive cycling of the potential. Unlike the case in ionic liquids, [PD][PF6]3 is thermodynamically insoluble in water, although oxidized forms are believed to have an anion dependent level of solubility. Consequently, an oxidation - dissolution/reduction - reprecipitation and ion exchange type mechanism is believed to lead to a transition from the "thick" to "thin" film type of voltammetric behavior, which is supported by numerical simulation.

A series of podands based on two or three hydrogen bonding "arms" situated in mutually ortho, meta, or para relationships about an aryl core have been prepared, and their affinities for simple inorganic anions were measured. Of the two-arm hosts the meta compound and to a lesser extent the ortho host exhibit a cooperative anion binding effect. The two arms function essentially independently in the para derivative. The mutually meta three-arm host shows dramatically enhanced cooperative binding. Conformational changes within the meta two-arm host result in significantly enhanced electrochemical anion sensing compared with the more conformationally rigid three-arm host.

A series of conjugated mixed metal heteroporphyrin dimers has been prepared using Wittig chemistry. They can be synthesized from a double Wittig reaction between porphyrin phosphonium salts and phthalaldehydes, or from stepwise Wittig reactions. This allows both symmetrical and unsymmetrical dimers to be prepared with complete control of porphyrin metallation. Copyright © 2002 Society of Porphyrins & Phthalocyanines.

A new channel-containing 1D coordination polymer has been prepared by the combination of a linear dimetallic spacer, Cu2(O2CMe)4, and a linear didentate ligand, 1,3-di-4-pyridylpropane; the new material includes methanol, acetic acid and diethylene glycol. © 2002 The Royal Society of Chemistry.

A series of podands based on three hydrogen bonding ¿arms¿ have been prepared and their affinities for simple inorganic anions measured. © 2002 Royal Society of Chemistry.

A series of podands based on three hydrogen bonding ¿arms¿ have been prepared and their affinities for simple inorganic anions measured. © 2002 Royal Society of Chemistry.

The preparation and structures of a variety of oxonium ion tetrachloroaurate(III) salts isolated from aqua regia are reported. The new compounds are [(H5O2)2(12-crown-4)2] [AuCl4]2 (1), [(H7O3)(15-crown-5)][AuCl4] (2), [(H5O2)(benzo-15-crown-5)2] [AuCl4] (3), [(H3O)(18-crown-6)][AuCl4] (4), [(H5O2)(dibenzo-24-crown-8)][AuCl4] (5), [(H5O2)(4-nitrobenzo-15-crown-5)2] [AuCl4] (6), [(H3O)(4-nitrobenzo-18-crown-6)][AuCl4] (7), [(H11O5)-(tetrachlorodibenzo-18-crown-6)2] [AuCl4] (8), and [(H7O3)(dinitrodibenzo-30-crown-10)][AuCl4] (9). A significant correlation between the degree of proton hydration and crown ether size is observed. Aryl crown ethers are nitrated in concentrated aqua regia, but nonnitrated products may be obtained in a dilute solution of aqua regia by reaction with aqueous HAuCl4.

A facile synthesis of trimeric porphyrins is reported. The geometry of the terminal porphyrins relative to the central macrocycle can be varied without significant changes to the synthetic procedure. This procedure also enables systematic control over the metallation states of the trimeric porphyrins.

The oxidative addition of alkyl iodides to the tin(II) complex of the 6,8,15,17-tetramethyl-5,9,14,18-tetraazadibenzo-[14]annulene dianion, Sn(tmtaa), in THF produced cationic, five-co-ordinate complexes [Sn(tmtaa)(R)]I, where R = Me, Et, n-Pr or n-Bu. Diiodomethane added to two equivalents of Sn(tmtaa) to give the CH2 bridged dication [{Sn(tmtaa)}2(µ-CH2)]I2. The new alkyl complexes are all air stable in solution and the solid state. Two of the complexes, [Sn(tmtaa)Me]I·2CHCl3 and [{Sn(tmtaa)}2(µ-CH2)]I 2·LiI·3H2O, have been characterised by single crystal X-ray diffraction studies, which confirms the five-co-ordinate geometry of the cations.

Conductive transparent carbon thin film electrodes have been grown on a copper foil using poly(methyl methacrylates) as a carbon source at a temperature below 450 °C, in contrast to the preparation temperature above 800 °C in the previously reported chemical vapour deposition method. Raman and UV-Vis absorption spectroscopy have been used to identify their graphene based composition. Scanning electron microscopy and Transmission electron microscopy have been used to characterize the film quality. Conductivity and transmittance of the thin films have been evaluated. Using the conductive transparent electrodes, organic solar cells have been successfully fabricated. This work paves a potential pathway for an easier and cheaper production of organic solar cells. © 2013 IEEE.

Sensing moiteies may be covalently attached to glassy carbon by reduction of functionalised diazonium salts [1,2]. The attachment of glucose oxidase with a cinnamic acid linker provides an example of simple tethering using this technique. An electrode formed in this way exhibits little susceptibility to interference from ascorbic acid and 4-acetamidophenol. A pH-reponsive (56.18 mV decade-1) glassy carbon electrode is formed by grafting quinone groups to the electrode with stilbene linkers.