V. Ganesh

Controlled Growth of Gold Nanostars: Effect of Spike Length on SERS Signal Enhancement

Two different types of gold nanostars (Au NS), namely, short-spiked nanostars (SSNS) and long-spiked nanostars (LSNS), are prepared by using a hexagonal lyotropic liquid-crystalline (LLC) phase as a template. The formation, size and length of spikes or arms of the resultant Au NS are controlled by preparation in either a hexagonal LLC phase or an isotropic phase. These NS are anchored onto indium tin oxide (ITO) electrodes through a self-assembled monolayer of 3-mercaptopropyltrimethoxysilane, which acts as a linker molecule. Structural and morphological characterisations of SSNS- and LSNS-anchored ITO electrodes are performed by means of microscopic and spectroscopic analyses. Further electrochemical techniques, namely, cyclic voltammetry and electrochemical impedance spectroscopy, are also used to confirm the immobilisation of these Au NS on ITO electrodes and to study the electrochemical characteristics. These studies clearly reveal the formation of star-shaped, branched, anisotropic nanostructures of gold during the template preparation method and these Au NS are successfully anchored onto ITO electrodes through a covalent immobilisation strategy. Furthermore, the SERS activity of these Au NS is analysed by using glutathione and crystal violet as analytes and by employing glass and ITO as substrates. It is interesting to note that SSNS show a significant enhancement in SERS signals relative to those of LSNS.

Gold nanoparticles-immobilized, hierarchically ordered, porous TiO2 nanotubes for biosensing of glutathione.

Glutathione (GSH) is vital for several functions of our human body such as neutralization of free radicals and reactive oxygen compounds, maintaining the active forms of vitamin C and E, regulation of nitric oxide cycle, iron metabolism, etc. It is also an endogenous antioxidant in most of the biological reactions. Given the importance of GSH, a simple strategy is proposed in this work to develop a biosensor for quantitative detection of GSH. This particular biosensor comprises of gold nanoparticles (Au NPs)-immobilized, hierarchically ordered titanium dioxide (TiO2) porous nanotubes. Hexagonally arranged, honeycomb-like nanoporous tubular TiO2 electrodes are prepared by using a simple electrochemical anodization process by applying a constant potential of 30 V for 24 hours using ethylene glycol consisting of ammonium fluoride as an electrolytic medium. Structural morphology and crystalline nature of such TiO2 nanotubes are analyzed using field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). Interestingly, nanocomposites of TiO2 with Au NPs is prepared in an effort to alter the intrinsic properties of TiO2, especially tuning of its band gap. Au NPs are prepared by a well-known Brust and Schiffrin method and are immobilized onto TiO2 electrodes which act as a perfect electrochemical sensing platform for GSH detection. Structural characterization and analysis of these modified electrodes are performed using FESEM, XRD, and UV-visible spectroscopic studies. GSH binding events on Au NPs-immobilized porous TiO2 electrodes are monitored by electrochemical techniques, namely, cyclic voltammetry (CV) and chronoamperometry (CA). Several parameters such as sensitivity, selectivity, stability, limit of detection, etc are investigated. In addition, Au NPs dispersed in aqueous medium are also explored for naked-eye detection of GSH using UV-visible spectroscopy in order to compare the performance of the proposed sensor. Our studies clearly indicate that these materials could potentially be used for GSH sensing applications.

Structural, Optical and Magnetic Properties of NiO Nanopowders

Nickel oxide (NiO) nanopowders were synthesized without using surfactant by chemical reduction technique. NaBH4 influence on structural, optical and magnetic properties of NiO product was investigated. XRD results revealed the formation of dominant single phase, cubic face centered nickel oxide. Raman peaks depicts the characteristic first-order transverse optical (TO) phonon, two phonon excitation (TO + LO), excitation (2LO) Raman mode vibrations of face centered cubic NiO. PL studies revealed the presence of strong emission band which is in good agreement with the intrinsic NiO product. FTIR studies explored metal oxygen vibrations of the obtained product. TEM results revealed the nanoscale product with spherical shape structures. VSM studies explored weak ferromagnetic behavior of the obtained product. High concentration of NaBH4 increases magnetization value and exhibits the typical weak ferromagnetic curve. Reducing agent played a vital role in the structural, optical and magnetic properties of the obtained NiO product.

Structural, optical and magnetic properties of CuFe 2 O 4 nanoparticles

The manuscript presents structural, optical and magnetic properties of CuFe2O4 nanoparticles obtained employing a simple co-precipitation method in aqueous solution. Influence of ferric chloride concentration on the structural, optical and magnetic properties of CuFe2O4 nanoparticles was investigated. XRD results clearly revealed the spinel tetragonal copper ferrite structures. The observed characteristic Raman E1g, F2g and A1g phonon mode of vibrations revealed the tetragonal copper ferrite structures. The observed PL results explored inverse spinel copper ferrite emission peaks in the range of visible region. IR result revealed the metal oxygen intrinsic vibrations of octahedral and tetrahedral sites in the spinel copper ferrite structure. SEM analysis clearly revealed the spherical shape morphology particles sizes are in the nano scale range. VSM studies clearly revealed that copper ferrite exhibit weak ferromagnetic behaviour. It was found that the ferric chloride concentration added to copper chloride precursor in the ratio of 1:1, 1:2 and 1:3 during the synthesis process played a significant role in structural and magnetic properties of the obtained product.

Surfactant assisted zinc doped tin oxide nanoparticles for supercapacitor applications

AbstractZinc doped tin oxide nanoparticles were synthesized by employing sol–gel method assisted with different surfactants namely cetyl trimethyl ammonium bromide (CTAB), hexamine and polyethylene glycol 400 (PEG-400). The synthesis of uniform distribution of spherical Zn-SnO2 nanoparticles in presence of PEG-400 was optimized. The synthesized Zn-SnO2 nanoparticles were characterized by employing standard characterization techniques. X-ray diffraction results confirmed the product high-quality crystalline formation. The photoluminescence peaks appeared at 360u2009nm revealed the recombination of electron and hole from band to band emission of SnO2 optical properties. The vibrational properties of Zn-SnO2 nanoparticles were confirmed by both Raman and infra red spectra. The spherical morphology and nano sized product was evident in 200u2009nm scale SEM images. The cyclic voltammetry result of the product Zn-SnO2 assisted PEG-400 exhibited the specific capacitance value of 312.7u2009F/g at scan rate of 10u2009mV/s and revealed the superior electrochemical properties. Moreover, the EIS and GCD studies also revealed the good supercapacitor nature with specific capacitance of 132.1u2009F/g at current density of 1u2009A/g for the product Zn-SnO2 (PEG-400).n Diagrammatic representation of Zn doped SnO2 synthesis by sol-gel method with enhanced specific capacitance of 132.1u2009F/g at 1u2009A/g for Zn-SnO2 (PEG-400).HighlightsZn-SnO2 nanoparticles in presence of PEG-400 was optimizedZn-SnO2 (PEG-400) nanoparticles exhibits superior electrochemical propertiesProduct exhibits good capacitance (132.1u2009F/g) at 1u2009A/g current density

Zinc oxide nanotips growth by controlling vapor deposition on substrates

ZnO nanotips structure fabrication was undertaken through controlled growth by chemical vapor deposition (CVD) method. Substrate position and deposition time role was investigated systematically by controlling the parameters such as temperature, flow rate, and growth pressure. The obtained result showed that ZnO nanorods undergo a sharp regrowth process with increase in ZnO vapor availability in the CVD reactor. The surface morphology and structural properties were investigated by using field-emission scanning electron microscopy and X-ray diffraction (XRD) techniques. The grown nanostructures were used for gas sensor fabrication to detect and to study the sensitivity effects of H2 and CO.

Pseudocapacitive NiO/NiSnO3 Electrode for Supercapacitor Applications

NiO/NiSnO3 nanocomposite synthesis was accomplished by a hydrothermal method. The role of polyvinylpyrrolidone and experimental parameters in the configuration of NiO/NiSnO3 nanocomposite was studied by employing standard characterization techniques. Electrochemical properties were demonstrated by adopting cyclic voltammetry, electro-impedance spectra and galvanostatic charging and discharging studies. All the obtained products have contact resistance Rct of 0.72xa0Ω at low frequency arising from the resistance between the working electrode and the electrolyte. The NiO/NiSnO3 nanocomposite superior properties may arise from nanosized rod morphology due to their inherent properties having a significant impact on their electrochemical properties. The specific capacitance for RSA3 can be estimated as 524xa0F/g at a current density of 0.5xa0A/g.

Exopolysaccharide from Bacillus cereus VK1: Enhancement, characterization and its potential application in heavy metal removal

Increasing interests in industrialization invites acute or chronic toxicity into the environment resulting in serious ecological risks. This can be efficiently handled by bioremediation techniques. Hence in the present study, an exopolysaccharide (EPS) producing bacterium was isolated and identified as Bacillus cereus VK1 by 16S rRNA characterization. EPS was purified, estimated and further characterized by FTIR, GC-MS and TGA. Media optimization for enhanced production of EPS was done by statistical modeling which yielded a 15.49 fold increase upon supplementation of molasses (3%) and soy meal (3%). Furthermore, the cells were employed for bioremediation of Hg2+, estimated by stripping voltammetry technique. Results revealed that 20u2009mg (DCW) of Bacillus cereus VK1, grown in LB could adsorb up to 80.22u2009μg Hg2+ in 20u2009min, whereas bacteria grown in the RSM optimized M9 media adsorbed up to 295.53u2009μg Hg2+, thus B.cereus VK1 may render a strategy for the bioremediation of Hg2+ polluted eco-systems.

Electrochemically active X WO 4 ( X = Co, Cu, Mn, Zn) nanostructure for water splitting applications

Electrochemically active XWO4 (Xu2009=u2009Co, Cu, Mn, Zn) nanostructures were synthesized successfully by employing solvothermal method. The processing parameters’ effect such as time, temperature, pH and solvents on morphological and electrochemical OER performance of XWO4 nanostructures was investigated. The excellent OER response was observed for XWO4 nanostructures synthesized at optimum processing condition. The synthesized samples’ superior electrochemical performance was found to be in the following order CoWO4u2009>u2009MnWO4u2009>u2009CuWO4u2009>u2009ZnWO4 by employing CV and LSV studies. The electrochemical impedance spectroscopic analysis was done for all the samples. Good stability over 3600xa0s was reported for the best-performed samples of XWO4 nanostructures.