Ananthakumar Ramadoss

Enhanced activity of a hydrothermally synthesized mesoporous MoS2 nanostructure for high performance supercapacitor applications

In the present work, we have synthesized a mesoporous molybdenum disulfide (MoS2) nanostructure by a facile hydrothermal route for supercapacitor applications. FE-SEM and TEM images confirmed the mesoporous morphologies of the as-prepared samples. The electrochemical measurements showed that the as-prepared mesoporous MoS2 electrode delivered maximum capacitances of 376 and 403 F g−1 at a scan rate of 1 mV s−1 in 1 M Na2SO4 and KCl electrolyte solutions respectively, which indicated that the mesoporous MoS2 nanostructure was a suitable electrode material for supercapacitor applications.

Piezoelectric-Driven Self-Charging Supercapacitor Power Cell

In this work, we have fabricated a piezoelectric-driven self-charging supercapacitor power cell (SCSPC) using MnO2 nanowires as positive and negative electrodes and a polyvinylidene difluoride (PVDF)-ZnO film as a separator (as well as a piezoelectric), which directly converts mechanical energy into electrochemical energy. Such a SCSPC consists of a nanogenerator, a supercapacitor, and a power-management system, which can be directly used as a power source. The self-charging capability of SCSPC was demonstrated by mechanical deformation under human palm impact. The SCSPC can be charged to 110 mV (aluminum foil) in 300 s under palm impact. In addition, the green light-emitting diode glowed using serially connected SCSPC as the power source. This finding opens up the possibility of making self-powered flexible hybrid electronic devices.

Fabrication of reduced graphene oxide/TiO2 nanorod/reduced graphene oxide hybrid nanostructures as electrode materials for supercapacitor applications

Two-dimensional (2D) reduced graphene oxide/titanium dioxide nanorod array/reduced graphene oxide (rGO/TiO2 NR/rGO) with a porous hybrid structure was fabricated as an electrode material for use in electrochemical supercapacitors. The structural, morphological, and compositional characteristics of the resulting electrode material were evaluated by using X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), and X-ray photoelectron spectroscopy (XPS). The electrochemical behavior of the as-prepared electrodes was characterized by using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) in 1 M Na2SO4 aqueous electrolyte. The maximum specific capacitance of this rGO/TiO2 NR/rGO electrode was 114.5 F g−1 at a scan rate of 5 mV s−1. The electrode exhibited high cycling stability, retaining over 85% of its initial capacitance after 4000 cycles. These results indicate that rGO/TiO2/rGO is a promising candidate for the electrode material in supercapacitor applications.

Bio-molecule Assisted Aggregation of ZnWO4 Nanoparticles (NPs) into Chain-like Assemblies: Material for High Performance Supercapacitor and as Catalyst for Benzyl Alcohol Oxidation

ZnWO4 nanoparticles (NPs) that are assembled and aggregated together as chain-like morphology have been synthesized via the reaction of Zn(II) salt solution with sodium tungstate in the presence of the DNA scaffold under 5 min of microwave heating. The reaction parameters have been tuned to control the size of the individual particles and diameter of the chains. The significance of different reaction parameters and specific growth mechanism for the formation of particles is elaborated. The DNA-ZnWO4 nanoassemblies have been used in two potential applications for the first time, namely, supercapacitor and catalysis studies. Supercapacitor study revealed that DNA-ZnWO4 nanoassemblies exhibited good electrochemical properties having high specific capacitance value ∼72 F/g at 5 mV s(-1), and electrodes possessed a good cyclic stability with more than 1000 consecutive times of cycling. Catalysis studies have been done for benzyl alcohol oxidation, and it was observed that DNA-ZnWO4 nanoassemblies having smaller diameter gives better catalytic efficiency compared to other morphology. This is further authenticated from their BET surface area analysis. In the future, the self-assembled DNA-ZnWO4 nanoassemblies could be a promising candidate for the synthesis of other mixed metal oxides and should be applicable in various emerging fields like Li ion batteries or photocatalysis, or as luminescent materials.

Resistive Switching Behaviors of HfO2 Thin Films by Sol-Gel Spin Coating for Nonvolatile Memory Applications

In this study, we reported the fabrication of a transparent resistive random access memory device based on the Ag/HfO2/indium tin oxide (ITO) capacitor structure and its resistive switching characteristics. The X-ray diffraction and Fourier transform infrared spectra demonstrated that the as grown HfO2 thin films were monoclinic in structure. The morphological analysis revealed a uniform, smooth surface morphology of the thin films. The fabricated Ag/HfO2/ITO memory device exhibited the characteristic of bipolar resistive switching under a consecutive dc sweeping voltage of ±2 V. The mechanism of the resistive switching in the fabricated memory device is examined on the basis of the reversible formation/rupture of the conducting filament in the oxygen-deficient HfO2 layer.

Supercapacitor and dye-sensitized solar cell (DSSC) applications of shape-selective TiO2 nanostructures

Shape-selective TiO2 nanomaterials with different morphology, namely wire-like, flake-like and flower-like, have been synthesized by utilizing a simple wet chemical route by the reaction of titanium isopropoxide with ethanol and water mixture in the presence of cetyltrimethylammonium bromide. The shape of the particles can be easily tuned by altering the concentration of surfactant relative to the metal salt and changing the other reaction parameters. The formation mechanism of different shapes has been elaborated in detail. The shape-selective TiO2 nanomaterials have been utilized for electrochemical supercapacitor and DSSC applications. It was observed that TiO2 nanomaterials with various shapes showed different specific capacitance (Cs) values, and the order of Cs values is as follows: wire-like > flower-like > flake-like. The highest Cs of 3.16 F g−1 and better cycling stability was observed for TiO2 nanomaterials having wire-like shapes. At a high scan rate 150 mV s−1, the capacitance retention of wire-like TiO2 electrode remains at about 90% after 5000 cycles. DSSC study results show that all the differently shaped TiO2 nanomaterials can be used as potential anode materials, and, among the different shapes, the flower-like morphology shows better photo-conversion efficiency. The presented synthesis process is fast, cost-effective and environmentally friendly and could be utilized for other applications like gas sensors, photo-catalysts or elimination of pollutants from contaminated soils.

Studies of calcium-precipitating oral bacterial adhesion on TiN, TiO2 single layer, and TiN/TiO2 multilayer-coated 316L SS

Titanium nitride (TiN), titanium oxide (TiO2) single layer, and TiN/TiO2 multilayer coatings were deposited on a 316L stainless steel substrate using reactive magnetron sputtering process with the aim of preventing bacterial adhesion. The crystal structures of as-prepared coatings were evaluated using X-ray diffraction analysis. The cubic structure of TiN, anatase, and rutile structure of TiO2 was noticed. Atomic force microscopy images exhibited a relatively smooth surface for all coatings. The surface wettability studies confirmed that the coatings were hydrophilic in nature. The rate of bacterial adhesion was evaluated using scanning electron microscopy and epifluorescence microscopy. These results demonstrated that the coated substrates could help to effectively reduce the bacterial adhesion and biofilm formations.

Corrosion, haemocompatibility and bacterial adhesion behaviour of TiZrN-coated 316L SS for bioimplants

TiZrN coating was deposited on 316L stainless steel (SS) by the reactive magnetron co-sputtering technique. Cubic phase of TiZrN with uniform surface morphology was observed by X-ray diffraction and atomic force microscopy. Bacterial adhesion, haemocompatibility and corrosion behaviour of TiZrN coating were examined in order to evaluate the coating’s compatibility for ideal implant. Results revealed that TiZrN coatings exhibited less bacterial attachment against Staphylococcus aureus and Escherichia coli bacteria, negligible platelets activation and superior corrosion resistance than the uncoated 316L SS.

Bacterial Adhesion and Hemocompatibility Behavior of TiN, TiO2 Single and TiN/TiO2 Multilayer Coated 316L SS for Bioimplants

Magnetron sputtering techniques was used to deposit TiN, TiO2 single layer and TiN/TiO2 multilayer coatings on 316L stainless steel (316L SS) substrates. The crystallinity, surface topography and roughness parameters of uncoated (316L SS) and coated specimens were examined. The anti adhesion and antibacterial behavior of S.aureus (gram (+) ve) and E.coli (gram (-) ve) strains on uncoated and coated substrates were determined by live/dead staining using epifluorescence microscopy. Results demonstrate that the coated samples undergo drastic reduction of bacterial adhesion and negligible effect of antimicrobial activity. Further, coated substrates exhibit less platelets activation than that of uncoated substrates.