Electropolymerization of Uniform Polyaniline Nanorod Arrays on Conducting Oxides as Counter Electrodes in Dye-Sensitized Solar Cells.

Conventional techniques for the synthesis of oriented polyaniline (PANI) nanostructures are often complex or time consuming. Through an innovative reduced graphene oxide (rGO) modified FTO and a low-potential electropolymerization strategy, the rapid and template-free growth of a highly ordered PANI nanorod array on the FTO substrate is realized. The highly ordered nanostructure of the PANI array leads to a high electrocatalytic activity and chemical stability. The importance of the polymerization potential and rGO surface modification to achieve this nanostructure is revealed. Compared to platinum, the PANI nanorod array exhibits an enhanced performance and stability as counter electrodes in dye-sensitized solar cells, with a 17.6 % enhancement in power conversion efficiency.

A new strategy for achieving vertically-erected and hierarchical TiO2 nanosheets array/carbon cloth as a binder-free electrode for protein impregnation, direct electrochemistry and mediator-free glucose sensing.

We present a new approach to directly grow uniform and highly-ordered TiO2 nanosheets array (NSA) on a low-cost flexible carbon cloth substrate while simultaneously fulfill precise TiO2 nanostructure tailoring and crystal phase control. The unique vertically-erected TiO2 NSA/carbon cloth with hierarchical structures was directly explored as electrode for enzyme immobilization and biosensing applications without suffering any influences of insulating binders usually used to fix nanomaterials on conductive substrates during sensor fabrications. Efficient direct electron transfer was successfully achieved for glucose oxidase (GOx) immobilized on the TiO2 NSA/carbon cloth, which produces a stable, mediator-free glucose sensor with good selectivity, high-sensitivity (52 µA mM(-1)cm(-2)), low response time (<5s) and low detection limit (23.4 µM, S/N=3). The mechanism of the superior direct electrochemical properties and sensing performance was investigated in detail, and discussed from the aspects of material nanostructure and crystalline form of TiO2 NSA, and an intimate contact between TiO2 and carbon cloth resulted from direct crystallization and growth of TiO2 nanosheets on the substrate.

Hierarchical Ni-Mo-S nanosheets on carbon fiber cloth: A flexible electrode for efficient hydrogen generation in neutral electrolyte.

A unique functional electrode made of hierarchal Ni-Mo-S nanosheets with abundant exposed edges anchored on conductive and flexible carbon fiber cloth, referred to as Ni-Mo-S/C, has been developed through a facile biomolecule-assisted hydrothermal method. The incorporation of Ni atoms in Mo-S plays a crucial role in tuning its intrinsic catalytic property by creating substantial defect sites as well as modifying the morphology of Ni-Mo-S network at atomic scale, resulting in an impressive enhancement in the catalytic activity. The Ni-Mo-S/C electrode exhibits a large cathodic current and a low onset potential for hydrogen evolution reaction in neutral electrolyte (pH ~7), for example, current density of 10 mA/cm(2) at a very small overpotential of 200 mV. Furthermore, the Ni-Mo-S/C electrode has excellent electrocatalytic stability over an extended period, much better than those of MoS2/C and Pt plate electrodes. Scanning and transmission electron microscopy, Raman spectroscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and x-ray absorption spectroscopy were used to understand the formation process and electrocatalytic properties of Ni-Mo-S/C. The intuitive comparison test was designed to reveal the superior gas-evolving profile of Ni-Mo-S/C over that of MoS2/C, and a laboratory-scale hydrogen generator was further assembled to demonstrate its potential application in practical appliances.

Cesium carbonate functionalized graphene quantum dots as stable electron-selective layer for improvement of inverted polymer solar cells.

Solution processable inverted bulk heterojunction (BHJ) polymer solar cells (PSCs) are promising alternatives to conventional silicon solar cells because of their low cost roll-to-roll production and flexible device applications. In this work, we demonstrated that Cs2CO3 functionalized graphene quantum dots (GQDs-Cs2CO3) could be used as efficient electron-selective layers in inverted PSCs. Compared with Cs2CO3 buffered devices, the GQDs-Cs2CO3 buffered devices show 56% improvement in power conversion efficiency, as well as 200% enhancement in stability, due to the better electron-extraction, suppression of leakage current, and inhibition of Cs(+) ion diffusion at the buffer/polymer interface by GQDs-Cs2CO3. This work provides a thermal-annealing-free, solution-processable method for fabricating electron-selective layer in inverted PSCs, which should be beneficial for the future development of high performance all-solution-processed or roll-to-roll processed PSCs.

Electrochemical fabrication of ZnO-CdSe core-shell nanorod arrays for efficient photoelectrochemical water splitting.

Efficient hydrogen production from photoelectrochemical (PEC) water splitting is a promising route to solve the approaching energy crisis. Herein, we report a facile all-electrochemical approach to fabricate well-aligned ZnO-CdSe core-shell nanorod arrays with excellent uniformity on transparent indium tin oxide (ITO) substrates. The shell thickness of the core-shell nanorods can be tuned precisely by adjusting the charge density passing through the working electrode during the deposition of CdSe quantum dots (QDs). The optimized ZnO-CdSe nanorod arrays showed excellent PEC performance with a significant saturated photocurrent density of 14.9 mA cm(-2) at 0.8 V (vs. RHE) under AM 1.5 illumination, which is, to the best of our knowledge, the highest value ever reported for similar nanostructures, owing to the favourable band alignment and good distribution of CdSe QDs on ZnO nanorods. Our results demonstrate that the electrochemically deposited ZnO-CdSe nanorod arrays can be utilized as efficient photoanodes in PEC water splitting cells.

RGD-peptide functionalized graphene biomimetic live-cell sensor for real-time detection of nitric oxide molecules.

It is always challenging to construct a smart functional nanostructure with specific physicochemical properties to real time detect biointeresting molecules released from live-cells. We report here a new approach to build a free-standing biomimetic sensor by covalently bonding RGD-peptide on the surface of pyrenebutyric acid functionalized graphene film. The resulted graphene biofilm sensor comprises a well-packed layered nanostructure, in which the RGD-peptide component provides desired biomimetic properties for superior human cell attachment and growth on the film surface to allow real-time detection of nitric oxide, an important signal yet short-life molecule released from the attached human endothelial cells under drug stimulations. The film sensor exhibits good flexibility and stability by retaining its original response after 45 bending/relaxing cycles and high reproducibility from its almost unchanged current responses after 15 repeated measurements, while possessing high sensitivity, good selectivity against interferences often existing in biological systems, and demonstrating real time quantitative detection capability toward nitric oxide molecule released from living cells. This study not only demonstrates a facial approach to fabricate a smart nanostructured graphene-based functional biofilm, but also provides a powerful and reliable platform to the real-time study of biointeresting molecules released from living cells, thus rendering potential broad applications in neuroscience, screening drug therapy effect, and live-cell assays.

Improved utilization of photogenerated charge using fluorine-doped TiO(2) hollow spheres scattering layer in dye-sensitized solar cells.

We demonstrate a strategy to improve utilization of photogenerated charge in dye-sensitized solar cells (DSSCs) with fluorine-doped TiO2 hollow spheres as the scattering layer, which improves the fill factor from 69.4% to 74.1% and in turn results in an overall efficiency of photoanode increased by 13% (from 5.62% to 6.31%) in comparison with the control device using undoped TiO2 hollow spheres. It is proposed that the fluorine-doping improves the charge transfer and inhibition of charge recombination to enhance the utilization of the photogenerated charge in the photoanode.