S. Arunmetha

Enhanced functional properties of cotton fabrics using TiO2/SiO2 nanocomposites:

Anatase titania (TiO2) nanoparticles were prepared from natural minerals (rutile sand) using acid extraction by sol–gel method. The obtained X-ray diffraction results show that the particle possesses crystallite size of 12 nm. The colloidal silica and TiO2 nanoparticle-embedded colloidal silica solutions were prepared using sol–gel method followed by sonication process. The particle size was measured for the prepared colloidal TiO2/SiO2 sol. The prepared solution was coated on the surface of the cotton fabric through pad-dry-cure method. Elemental analysis confirms the presence of TiO2/SiO2 nanocomposite along with cellulose on the surface of the fabric. The washing durability of the coated fabrics after fifth and 10th washes indicates that the nanoparticles strongly adhered to the fabric surface. The ultraviolet resistance, burning performance, and antibacterial activity against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria of TiO2/SiO2-coated fabric were found to be better than those of un-coated fabrics before and after washing.

Electrochemical capacitor study of spherical MnO2 nanoparticles utilizing neutral electrolytes

In this study, we report the synthesis of spherical MnO2 nanoparticles using spray pyrolysis method. The synthesized particles were characterized by powder X-ray diffraction, Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The SEM image showed spherical nanoparticles with average size of 65 nm, which was in agreement with the TEM measurement. The results of the N2 adsorption–desorption analysis indicated that the BET surface area of the spherical nanoparticles was 102 m2 g-1 with the pore size diameter of 15.18 nm. The electrochemical measurements such as cyclic voltammetry and electrochemical impedance spectroscopy were made in the solution of 0.1 M Li2SO4 and Na2SO4 electrolytes. At lower scan rates the Na2SO4 electrolyte showed a maximum specific capacitance of 68 F g-1 whereas in the Li2SO4 electrolyte it was found to be 63 F g-1. Moreover, Nyquist plot revealed that Na2SO4 electrolyte had a lower charge transfer resistance (Rct) value when compared to Li2SO4 electrolyte.

Study on Production of Silicon Nanoparticles from Quartz Sand for Hybrid Solar Cell Applications

Nano silicon (nano Si) particles were directly prepared from natural mineral quartz sand and thereafter used to fabricate the hybrid silicon solar cells. Here, in this preparation technique, two process stages were involved. In the first stage, the alkaline extraction and acid precipitation processes were applied on quartz sand to fetch silica nanoparticles. In the second stage, magnesiothermic and modified magnesiothermic reduction reactions were applied on nano silica particles to prepare nano Si particles. The effect of two distinct reduction methodologies on nano Si particle preparation was compared. The magnesiothermic and modified magnesiothermic reductions in the silica to silicon conversion process were studied with the help of x-ray diffraction (XRD) with intent to study the phase changes during the reduction reaction as well as its crystalline nature in the pure silicon phase. The particles consist of a combination of fine particles with spherical morphology. In addition to this, the optical study indicated an increase in visible light absorption and also increases the performance of the solar cell. The obtained nano Si particles were used as an active layer to fabricate the hybrid solar cells (HSCs). The obtained results confirmed that the power conversion efficiency (PCE) of the magnesiothermically modified nano Si cells (1.06%) is much higher as compared to the nano Si cells that underwent magnesiothermic reduction (1.02%). Thus, this confirms the increased PCE of the investigated nano Si solar cell up to 1.06%. It also revealed that nano Si behaved as an electron acceptor and transport material. The present study provided valuable insights and direction for the preparation of nano Si particles from quartz sand, including the influence of process methods. The prepared nano Si particles can be utilized for HSCs and an array of portable electronic devices.