P. Sudhagar

Synergistic Catalytic Effect of a Composite (CoS/PEDOT:PSS) Counter Electrode on Triiodide Reduction in Dye-Sensitized Solar Cells

Inorganic/organic nanocomposite counter electrodes comprised of sheetlike CoS nanoparticles dispersed in polystyrenesulfonate-doped poly(3,4-ethylenedioxythiophene (CoS/PEDOT:PSS) offer a synergistic effect on catalytic performance toward the reduction of triiodide for dye-sensitized solar cells (DSSCs), yielding 5.4% power conversion efficiency, which is comparable to that of the conventional platinum counter electrode (6.1%). The electrochemical impedance spectroscopy (EIS) and cyclic voltammetry measurements revealed that the composite counter electrodes exhibited better catalytic activity, fostering rate of triiodide reduction, than that of pristine PEDOT: PSS electrode. The simple preparation of composite (CoS/PEDOT:PSS) electrode at low temperature with improved electrocatalytic properties are feasible to apply in flexible substrates, which is at most urgency for developing novel counter electrodes for lightweight flexible solar cells.

A mechanically bendable superhydrophobic steel surface with self-cleaning and corrosion-resistant properties

We present an effective way to develop superhydrophobic steel surface which shows stable superhydrophobicity under harsh mechanical bending. The roughness on the steel surface was created by etching in acid solution and its surface energy was lowered by subsequent hydrophobic silane treatment. The steel etching time in sulfuric acid solution was optimized to 8 h which provides high surface roughness required for superhydrophobicity. A water contact angle of 164 ± 3° and a sliding angle of 9 ± 2° were obtained for the steel surface after surface chemical modification by methyltrichlorosilane. We bent this superhydrophobic steel to 90° and 180° and studied the wetting properties on the bent area, which showed absolutely no change in superhydrophobicity. This superhydrophobic steel surface showed excellent self-cleaning behaviour as well as maintained its superhydrophobic wetting properties under a stream of water jet. Further, the stability of the wetting state was evaluated using a sandpaper abrasion test, adhesive tape peeling test, and under prolonged UV irradiation. Energy-dispersive X-ray spectroscopy was used to confirm the surface chemical composition of the superhydrophobic steel surface. This approach can be applied to steel surfaces of any size and shape to advance their industrial applications.

Effect of HNO3 functionalization on large scale graphene for enhanced tri-iodide reduction in dye-sensitized solar cells

Improving the electro-catalytic activity of graphene has recently been the subject of intense research for high efficiency flexible energy storage and conversion devices. We report the synthesis of a large scale graphene film by a CVD method and its electro-catalytic activity by functionalization with HNO3 for a high efficiency electrochemical electrode in DSSCs. We found that HNO3 functionalization on graphene enhances the tri-iodide reduction rate by three times in a dye sensitized solar cell compared to that of pristine graphene. The X-ray photoelectron spectroscopy (XPS) and ultra-violet photoemission spectroscopy (UPS) studies confirm the covalently attached C–OH, C(O)OH and NO3− moieties to carbon atoms through sp2–sp3 hybridization, and this results in the Fermi level shift towards p-type doping. We believe that the covalently attached functional groups cause the enrichment of the electro-catalytically active sites along with facilitating the charge transfer kinetics from graphene counter electrodes to redox couples. The enhanced catalytic effect of functionalized graphene offers insights into new types of electrode development opportunities in graphene based energy storage and conversion devices.

Synergistic metal-metal oxide nanoparticles supported electrocatalytic graphene for improved photoelectrochemical glucose oxidation.

We report the fabrication of graphene-WO3-Au hybrid membranes and evaluate their photocatalytic activity towards glucose oxidase mediated enzymatic glucose oxidation. The dual-functionality of gold nanoparticles in the reinforcement of visible light activity of graphene-WO3 membranes and improving the catalytic activity of immobilized enzymes for unique photoelectrochemical sensing application is demonstrated. This work provides new insights into the fabrication of light-sensitive hybrid materials and facilitates their application in future.

A PEDOT-reinforced exfoliated graphite composite as a Pt- and TCO-free flexible counter electrode for polymer electrolyte dye-sensitized solar cells

Herein, we have demonstrated a highly efficient, flexible, and low-cost (Pt-free and TCO-free) counter electrode made of a highly conductive poly(3,4-ethylene dioxythiophene) (PEDOT)/exfoliated graphite (EFG) composite in solid state dye-sensitized solar cells (DSSCs) employing polymer electrolytes. Electropolymerized one-dimensional PEDOT nanofibers were firmly attached to a flexible EFG sheet affording high catalytic activity and electron conductivity. PEDOT/EFG counter electrode-based DSSCs showed an energy conversion efficiency of 5.7% with a solid polymer electrolyte, which is significantly higher than conventional Pt electrodes (4.4%) under similar device architecture conditions.

Self-cleaning and superhydrophobic CuO coating by jet-nebulizer spray pyrolysis technique

We demonstrate for the first time the fabrication of a superhydrophobic CuO coating with excellent self-cleaning ability by a custom-made jet nebulizer spray pyrolysis technique. A stable Cassie–Baxter superhydrophobic wetting state (water contact angle, ~154°) was maintained even after high speed water jet impact on a monoclinic CuO crystallite coating, which realizes the robust feature of coating. The mist-type aerosol distribution from the nebulizer controls the resultant morphology of the CuO film, thereby tuning the superhydrophobic properties. The low-cost (~

Nanocomposite Coatings on Biomedical Grade Stainless Steel for Improved Corrosion Resistance and Biocompatibility

1) portable pocket-sized nebulizer affords reliable CuO superhydrophobic coatings on a wide range of desired host surfaces.

Interfacial engineering of quantum dot-sensitized TiO2 fibrous electrodes for futuristic photoanodes in photovoltaic applications

The 316 L stainless steel is one of the most commonly available commercial implant materials with a few limitations in its ease of biocompatibility and long-standing performance. Hence, porous TiO(2)/ZrO(2) nanocomposite coated over 316 L stainless steels was studied for their enhanced performance in terms of its biocompatibility and corrosion resistance, following a sol-gel process via dip-coating technique. The surface composition and porosity texture was studied to be uniform on the substrate. Biocompatibility studies on the TiO(2)/ZrO(2) nanocomposite coatings were investigated by placing the coated substrate in a simulated body fluid (SBF). The immersion procedure resulted in the complete coverage of the TiO(2)/ZrO(2) nanocomposite (coated on the surface of 316 L stainless steel) with the growth of a one-dimensional (1D) rod-like carbonate-containing apatite. The TiO(2)/ZrO(2) nanocomposite coated specimens showed a higher corrosion resistance in the SBF solution with an enhanced biocompatibility, surpassing the performance of the pure oxide coatings. The cell viability of TiO(2)/ZrO(2) nanocomposite coated implant surface was examined under human dermal fibroblasts culture, and it was observed that the composite coating enhances the proliferation through effective cellular attachment compared to pristine 316 L SS surface.

An electrochemical, in vitro bioactivity, and quantum chemical approach to nanostructured copolymer coatings for orthopedic applications

Herein we report generic surface treatment approaches to improve the electronic interfaces of quantum dot-sensitized TiO2 fiber electrodes, thereby promoting their photoanode performance. Highly dense, continuous and nanostructured TiO2 fibrous membranes, without the inclusion of a scattering layer, unlike conventional TiO2 particulate electrodes, showed feasible photoconversion performance under the proposed interfacial engineering modification. The proposed interfacial treatment concerns fibrous membranes both before and after calcination. The chemical vapor pre-treatment on an as-deposited fibrous membrane using tetrahydrofuran (THF) reinforces the physical contact between the fibrous membrane and the transparent conducting substrate and reduces significantly the recombination rate. In the case of post-treatment by F-ion on a fibrous surface, together with the interfacial engineering approach, the ZnS surface passivation layer markedly improves the photoanode performance of the TiO2 fibrous membrane nearly to a factor of 3.2% with a remarkable open-circuit voltage Voc = 0.69 V and Jsc = 13 mA cm−2 under 1 sun illumination (100 mW cm−2). This report provides an excellent platform for studying and understanding the interfacial contacts and mechanisms related to the charge transfer at CdS/CdSe QD-sensitized TiO2 fibrous assemblies. Such implications of this interfacial treatment strategy can be successfully extended to a wide range of photoanode candidates in energy conversion systems and confirm the effectiveness of some alternative nanostructured electrodes for the development of semiconductor-sensitized solar cells.

Successful demonstration of an efficient I-/(SeCN)2 redox mediator for dye-sensitized solar cells

Conducting polymers represent a promising platform toward coating materials for implant technologies in recent years. In this investigation, copolymers based on pyrrole (Py) and 3,4-ethylenedioxythiophene (EDOT) were electrodeposited on 316L SS with various feed ratio of Py/EDOT through cyclic voltammetric technique. The surface and chemical structure of the synthesized copolymers were analyzed by SEM, AFM, FT-IR, and 1H NMR spectroscopic analysis. The influence of comonomer feed ratio on electrochemical corrosion behavior was investigated in stimulated body fluid. A significant lower corrosion current with nobler shift in corrosion potential and higher charge transfer resistance values of copolymer-coated 316L SS were obtained and the comparisons were made with uncoated as well as their homo polymers. Furthermore, in vitro cell culture studies were performed on MG63 osteoblast human cells to confirm the biocompatibility of copolymer coatings. Quantum chemical approach was employed to verify the obtained experimental outcomes. As a result of this investigation, it was concluded that the performance of coatings was strongly dependent to the monomer feed ratio and the copolymer synthesized with 50:50 feed ratio showed high corrosion protection efficiency with improved cell growth on MG63 osteoblast cell.