A. Karthik

Hydrophobicity, flame retardancy and antibacterial properties of cotton fabrics functionalised with MgO/methyl silicate nanocomposites

In this study, we prepared MgO nanoparticles using a hot-air spray pyrolysis method. The prepared nanoparticles were characterised using X-ray diffraction (XRD) and the crystallite size was found to be 24 nm. Scanning electron microscopy (SEM) imaging showed needle-like morphology, which was also confirmed by transmission electron microscopy. Specific surface area (24 m2 g−1) of the MgO nanoparticles was analysed using the Barrett–Emmett–Teller method. Colloidal methyl silicate and MgO nanoparticle-embedded methyl silicate solutions were prepared using the sol–gel method. Cotton fabrics were separately functionalised with silica and MgO/methyl silicate composite using an optimised pad-dry-cure method. The phase and functional group of the coated and uncoated fabrics were analysed by XRD and Fourier transform infrared spectroscopy. The surface morphology of the coated fabrics was analysed using SEM. Elemental analysis, which was carried out using energy-dispersive spectroscopy, confirmed the presence of methyl silicate and MgO nanoparticles along with cellulose on the surface of the fabric. The washing durability of the coated fabrics after 5, 10 and 15 washes was assessed using SEM, confirming the adherence of nanoparticles on the surface of the fabric. The burning performance of the coated fabrics was in the order of MgO/methyl silicate (21.4 s) > methyl silicate (17.6 s) before and after washing. The cotton fabrics coated with MgO/methyl silicate composite showed a better antibacterial activity against Staphylococcus aureus and Escherichia coli than methyl silicate-coated and uncoated fabrics. In addition, the methyl silicate- and MgO/methyl silicate composite-coated cotton fabrics showed a significant water-repellent property with water contact angles of 135.2° and 138.6° for a 5 μl water droplet.

Size-dependent physicochemical properties of mesoporous nanosilica produced from natural quartz sand using three different methods

Mesoporous high-surface-area silica (SiO2) nanoparticles were produced from natural quartz sand (orthoquartzite) using three processing methods namely sol–gel, sonication, and spray pyrolysis. The inexpensive precursor was extracted from the quartz sand by alkali extraction followed by acid precipitation, which was used for all the three methods. The effects of production methods were investigated by various characterization techniques. The physicochemical properties of the obtained nanoparticles were compared to explore the effect of size and porosity on their electronic, optical, mechanical, and electrical qualities. The produced SiO2 nanoparticles were found to have an amorphous high surface area in the range of 178–322 m2 g−1 and a uniform size distribution with the high purity and spherical morphology. These particles formed a mesoporous material with an average pore diameter of 10–26 nm. It was found that the surface area (178 30 > 10 nm) when the process method was changed from sol–gel to sonication and from sonication to spray pyrolysis. This study provides useful insights and guidance for the preparation of mesoporous SiO2 nanoparticles from quartz sand and throws light on how physicochemical properties are influenced by process methods and particle size.

Nano-sized MnO2 particles produced by spray pyrolysis for a Zn/MnO2 primary cell: comparative discharge performance studies with their bulk counterparts

In this work, nano-sized spherical MnO2 particles with large surface area were synthesized employing spray pyrolysis for application in a Zn/MnO2 primary cell. Furthermore, we experimentally investigated the performance of nano-sized MnO2 particles when mixed with conductive additives, such as graphite and Vulcan carbon. The effect of particle size on the discharge performance of cells using two electrolytes (ZnCl2 and Zn(O2CCH3)2) was examined. To determine the crystalline phase, we comprehensively characterized microstructure, purity, particle size, thermal stability and surface area of both bulk and nano-sized particles. The measurements of electrochemical discharge characteristics, such as constant current discharge, cell capacity and internal resistance, were performed. From these discharge measurements, the nano-sized particle-based cathode (nano-sized MnO2/Vulcan carbon) discharge capacity was found to be 303 mA h g−1, which is 128% higher than the maximum value of the bulk MnO2 counterpart-based cathodes (bulk MnO2/Vulcan carbon). In addition, the internal resistance of the nano-sized MnO2/Vulcan carbon cathode-based cell appeared to be very low compared to that of all other bulk cathodes. Our results show that the configuration of nanoparticle-based cathode cells allows them to exhibit superior discharge capacity retention and increased shelf life compared to the conventional Zn/MnO2 cathode cells.

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.

Structural and Electrical Properties of Cadmium Sulfide Nanoparticles: A Simple Chemical Route

Structural and electrical properties of the nanocrystalline cadmium sulfide (CdS) powder were effectively synthesized and annealed at 573 K, 673 K and 773 K. Cadmium sulfate and sodium sulfide was used as a starting precursor for the preparation of CdS nanoparticles. The XRD results confirmed that major phase of hexagonal structure-CdS along with partial oxidation of CdO and CdSO3 nanoparticles. It reveals that the average crystallite size varies from 25 to 41 nm as annealing temperature increases. The phase and functional group composition was studied through FTIR. The average particle size distribution of CdS nanoparticles is 39, 47, and 49 nm for 573, 673, and 773 K, respectively. The surface morphology of CdS particles revealed the compact crystalline structure. Electrochemical impedance spectroscopy studies showed that the charge transfer resistance is lowered as annealing temperature is increased.