Prabhakarn Arunachalam

Facile synthesis of Fe3O4 nanorod decorated reduced graphene oxide (RGO) for supercapacitor application

The development of electrode materials capable of delivering high electrochemical performance is a major challenge. Herein, we demonstrate a facile approach for the synthesis of rod-shaped Fe3O4 nanostructures anchored on the reduced graphene oxide (RGO) surface and its application as an active electrode material for supercapacitors. The RGO–Fe3O4 nanocomposite was prepared by the spontaneous deposition of the rod-like FeOOH nanostructure onto the self-reduced GO surface followed by a thermal annealing process. The physical characterizations demonstrate the decoration of the rod-like Fe3O4 nanostructure over the RGO surface. Morphology analysis demonstrates that Fe3O4 nanorods with an average size of 150 nm are distributed over the RGO surface. The surface area analysis demonstrates that the as-synthesized RGO–Fe3O4 nanorod nanocomposite has 186 m2 g−1 specific surface area, which is higher compared to the Fe3O4 nanorods. As an active electrode material, the RGO–Fe3O4 nanocomposite shows excellent electrochemical performance compared to Fe3O4 nanorods. On the RGO–Fe3O4 nanocomposite based electrode a specific capacity of 315 C g−1 was observed at 5 A g−1 current density. Additionally, the RGO–Fe3O4 nanocomposite based electrode displayed excellent cycling stability with 95% specific capacity retention after 2000 cycles. The electrochemical results demonstrates that the RGO–Fe3O4 nanocomposite could be a promising material for energy conversion and storage.

A low cost additive-free facile synthesis of BiFeWO6/BiVO4 nanocomposite with enhanced visible-light induced photocatalytic activity

In this study, visible light driven BiFeWO6/BiVO4 nanocomposite was synthesized via simple additive-free wet-chemical process. Various physicochemical characterization methods such as X-ray diffraction (XRD), fourier transform infrared (FT-IR), scanning electron microscopy (SEM), transmission electrons microscopy (TEM), energy dispersive spectroscopy (EDS) spectra, UV visible diffuse reflectance spectroscopy (DRS), photoluminescence (PL) and photoelectrochemical measurements were performed to examine the structure, surface morphology, electrochemical and optical behavior of the synthesized material. The photocatalytic performances of the as-synthesized materials were assessed by the photodegradation of methylene blue (MB) in visible-light illumination. The optimum BiFeWO6/BiVO4-2 nanocomposite has shown 95% degradation efficiency of (MB) after 90min. This is about 10-folds higher than that of pristine bismuth vanadate (BiVO4). This enhancement of photocatalytic performances is credited to the photogenerated electrons transfer from BiVO4 to BiFeWO6 catalyst surface and thereby reduced the recombination process. The higher photocatalytic activity, long-term stability and recyclability results have revealed that the BiFeWO6/BiVO4 nanocomposite could be an auspicious material for the elimination of organic contaminants present in the ecosystem. Moreover, a probable mechanism for the catalytic degradation of MB dye over BiFeWO6/BiVO4 system is also proposed based on experimental results.

Bifunctional electro-catalytic performances of CoWO4 nanocubes for water redox reactions (OER/ORR)

In this paper, we report the synthesis of cube shaped nanoparticles of CoWO4 (∼30 nm) by molten salts and their bifunctional electro-catalytic activities in water redox reactions for oxygen evolution and oxygen reduction reactions (OER and ORR). Bifunctional performances of CoWO4 nano-cubes are explored for water electrolysis in an alkaline medium (1.0 M KOH) vs. reversible hydrogen electrode (RHE) under various atmospheres (N2, air and O2). Low overpotential (η10 = 0.45 V) of CoWO4 nano-cubes is accomplished at the current density of 10 mA cm−2. Tafel polarization curves (potential vs. log current density) reveal relatively lower slope values for OER (∼82 mV dec−1) and ORR (∼68 mV dec−1) compared to previous reports. Stability test of electrode materials has been performed using chrono-amperometry (CA) at fixed potential for 500 seconds. Kinetics and mobility of electrons have also been studied during the water redox reactions. Stable nature and enhanced bifunctional electro-catalytic performances of earth abundant CoWO4 electrodes could be used as the replacement of expensive electroactive noble electrode materials (Pt, Ir, Ru etc.) for water electrolysis (OER and ORR) in near future.

Phyllanthus emblica seed extract mediated synthesis of PdNPs against antibacterial, heamolytic and cytotoxic studies

Ecofriendly synthesis of Palladium nanoparticles (PdNPs) were achieved using Phyllanthus emblica (P. emblica) seeds as reducing agent. Further the ecofriendly synthesized PdNPs were subjected for various analytical techniques like UV-Vis, FT-IR, XRD, Zeta potential, SEM and TEM. The results indicated that green synthesized PdNPs were spherical in shape with average particle size of 28±2nm with moderate stability. Further the synthesized PdNPs and extract were subjected for its antibacterial studies against various disease causing pathogens by agar well diffusion method. Seed extract resulted in 8.9±1.46mm against B. subtilis and PdNPs showed 9.6±1.10mm against S. aureus and synthesized PdNPs and extract were tested for hemolytic which resulted in 20% and 10% respectively. Toxicity studies were done against Artemia salina (A. salina). The LC50 value of green synthesized P. emblica capped PdNPs and the P. emblica seed extract were found to be less toxic for A. salina with a value of 1.00μg/mL and 1.25μg/mL. In addition samples were checked for in vitro cytotoxicity assays on HeLa cell lines.

Electrochemical deposition of carbon materials incorporated nickel sulfide composite as counter electrode for dye-sensitized solar cells

The various carbon-based materials incorporated nickel sulfide (NiS) composites have been electrochemically deposited on fluorine-doped tin oxide (FTO) glass substrate. The structure, surface morphology, and elemental composition of the electrodeposited NiS composite materials were characterized by XRD, HR-SEM, and EDS. The electrochemically deposited various NiS composites such as NiS/AB (acetylene black), NiS/VC (Vulcan carbon), and NiS/MWCNT (multi walled carbon nanotubes) have been served as an efficient, low-cost counter electrode (CE) materials for dye-sensitized solar cells (DSSCs). Electrochemical impedance spectroscopy and cyclic voltammetry of NiS/AB CE composite materials exhibits a good conductivity and superior electrocatalytic performance over other various carbon incorporated materials. The positive synergistic effects, which increase the active catalytic sites and improved interfacial charge transfer, may be accountable for the superior electrocatalytic performance of NiS/AB composite materials The fabricated DSSC with NiS/AB CE reached a power conversion efficiency of 6.75%, which is equivalent with platinum electrode (7.20%). These results validate that the electrochemically deposited NiS/AB composite film is an auspicious alternative for low-cost and high efficient DSSCs.

A sensitive electrochemical detection of hydroquinone using newly synthesized α-Fe2O3-graphene oxide nanocomposite as an electrode material

This article presents the effect of hematite phase iron oxide (α-Fe2O3) on the electrocatalytic activity of graphene oxide (GO) for electrochemical detection of hydroquinone in aqueous solution. The different weight percentage (wt%) (1, 2 and 3%) of α-Fe2O3 added GO nanocomposites were synthesized by wet-impregnation method. The cyclic voltammetry studies using 2% α-Fe2O3-GO modified glassy carbon electrodes was found to exhibit an excellent electrocatalytic activity than α-Fe2O3 and GO electrodes that may be due to the synergistic effect of α-Fe2O3nanoparicles and GO sheet. In addition, the modified electrode exhibited a good reproducibility as well as long-term stability. Hence, the 2% α-Fe2O3-GO can be a promising catalytic material for electrochemical sensor applications.

Synthesis, characterization, multifunctional electrochemical (OGR/ORR/SCs) and photodegradable activities of ZnWO 4 nanobricks

AbstractBrick-shaped zinc tungstate nanoparticles have been synthesized by ecofriendly solvent-free process using molten salts. Zinc tungstate nanobricks (ZnWO4 Nbs) were characterized by powder x-ray diffraction (PXRD), FTIR, Raman, energy dispersive and electron microscopic studies. ZnWO4 Nbs are used as the multifunctional electrode materials to oxygen generation reactions (OGR), oxygen reduction reactions (ORR) and supercapacitors (SCs) as well as photo-catalysts in the waste-water treatment by the degradation of organic dyes. Low overpotential (ƞ10 = 0.475 V), low tafel slope (140 mV/dec), high current density (~70 mA/cm2) and good stability of the electrodes are the key results of the present studies for water electrolysis (OGR/ORR). ZnWO4 Nbs have also shown great interest in supercapacitors with efficient charge–discharge activities in 1 M KOH. The specific capacitance and energy density of ZnWO4 Nbs were found to be 250 F/g and 80 Wh/kg, respectively, at 5 mV/s, these values are relatively higher than that of previously reported specific capacitance and energy density value of metal tungstate nanoparticles. ZnWO4 Nbs as the photo-catalysts work very significantly for photocatalytic degradation of aqueous MB dye solution (~85 % in 3 h) in neutral medium. ZnWO4 Nanobricks show significant multifunctional electro-chemical activities in alkaline medium and photocatalytic degradation of organic dye in neutral medium.HighlightsEcofriendly solvent-free Synthesis of ZnWO4 Nanobricks (Nbs).ZnWO4 Nbs show admirable multifunctional electrochemical activities (OGR/ORR/SCs).Low overpotential, low Tafel values, relatively high current density and good stability of electrode materials are significant for OGR and ORR.ZnWO4 Nbs exhibit efficient supercapacitor performances with the specific capacitance (250 F/g) and energy density (80 Wh/kg) at 5 mV/s in 1 M KOH.ZnWO4 Nbs also work as photo-catalysts to enhance the degradation of aqueous organic dyes.

Catalytic application of non-toxic Persia americana metabolite entrapped SnO2 nanoparticles towards the synthesis of 3,4-dihydroacridin-1(2H)-ones

Eco-friendly methods in organic synthesis are dynamic prerequisites for environmental safety. In general, metal nanoparticles displayed various levels of toxicity, photocatalytic activity and catalytic activity. Due to their diverse properties, recent work has been focused towards the exploitation of plant sources in nanoparticle synthesis. Herein, we have highlighted the non-toxic studies of green synthesized SnO2 nanoparticles (SnO2 NPs) using Persia americana seed. The catalytic effects of SnO2 NPs were investigated on the synthesis of 3,4-dihydroacridin-1(2H)-ones. Synthesized compounds were confirmed using 1H NMR, 13C NMR and LCMS analysis. We proved that SnO2 NPs are non-toxic towards aquatic organisms.

Zinc Tantalum Oxynitride (ZnTaO2N) Photoanode Modified with Cobalt Phosphate Layers for the Photoelectrochemical Oxidation of Alkali Water

Photoanodes fabricated by the electrophoretic deposition of a thermally prepared zinc tantalum oxynitride (ZnTaO2N) catalyst onto indium tin oxide (ITO) substrates show photoactivation for the oxygen evolution reaction (OER) in alkaline solutions. The photoactivity of the OER is further boosted by the photodeposition of cobalt phosphate (CoPi) layers onto the surface of the ZnTaO2N photoanodes. Structural, morphological, and photoelectrochemical (PEC) properties of the modified ZnTaO2N photoanodes are studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet visible (UV−Vis) diffuse reflectance spectroscopy, and electrochemical techniques. The presence of the CoPi layer significantly improved the PEC performance of water oxidation in an alkaline sulphate solution. The photocurrent-voltage behavior of the CoPi-modified ZnTaO2N anodes was improved, with the influence being more prominent at lower oxidation potentials. A stable photocurrent density of about 2.3 mA·cm−2 at 1.23 V vs. RHE was attained upon visible light illumination. Relative to the ZnTaO2N photoanodes, an almost three-fold photocurrent increase was achieved at the CoPi/ZnTaO2N photoelectrode. Perovskite-based oxynitrides are modified using an oxygen-evolution co-catalyst of CoPi, and provide a new dimension for enhancing the photoactivity of oxygen evolution in solar-assisted water-splitting reactions.

Synthesis of calcium silicate nanoparticles and its catalytic application in Friedlander reaction

ABSTRACT This work describes the nitric acid catalysed synthesis of wollastonite (CaSiO3) nanoparticles (NP) from tetraethyl orthosilicate and calcium nitrate tetrahydrate. The formed calcium silicate nanoparticles were characterized by Fourier transform infrared spectroscopy (FTIR), Powder X-ray Diffraction (PXRD), and scanning electron microscopy (SEM) equipped with X-ray micro analysis. The CaSiO3 NPs showed an excellent yield (93%) towards the synthesis of quinolines via Friedlander reaction. The synthesized compound 3-dimethyl-7-nitro-9-phenyl-3,4-dihydroacridin-1(2H)-one was characterized by various spectroscopic techniques.