Venkatachalam Rajendran

Binder-free rice husk-based silicon–graphene composite as energy efficient Li-ion battery anodes

Rice husks, often neglected and considered as waste, contain constituents that could be of a potential use in advanced material applications. In this study, rice husks were used as a source of silicon dioxide for the synthesis of silicon nanoparticles (Si NPs) through magnesiothermic reduction process. The Si NPs were further used to prepare a binder-free composite system comprising Si NPs and graphene as an anode material for lithium ion battery system (LiBs). The composite system fabricated from rice husk-based Si NPs (RH-Si NPs) yielded an initial capacity of 1000 mA h g−1 at high applied current density of 1000 mA g−1. This study opens up the use of waste materials such as rice husk as a sustainable source of key components in advanced technology applications.

Influence of Nanosilica Powder on the Growth of Maize Crop (Zea Mays L.)

ABSTRACT A novel approach to study the effect of nanosilica on maize crop improvement was proposed. Nanosilica powders were mixed with soil at different concentrations along with control and conventional silica under in vitro and in vivo conditions. In in vitro, the nanosilica increases seed germination (2–11%), water usage efficiency (up to 53%), and total chlorophyll content (13–17%) of maize crop. In in vivo, influence of nanosilica was analyzed on basic parameters such as stem height, stem width, number of leaves, and silica content. The effect of nanosilica on maize crop was found to be enhanced in all aspects.

Effect of nanosilica and silicon sources on plant growth promoting rhizobacteria, soil nutrients and maize seed germination

The study was aimed at evaluating the effect of nanosilica and different sources of silicon on soil properties, total bacterial population and maize seed germination. Nanosilica was synthesised using rice husk and characterised. Silica powder was amorphous (50 nm) with >99.9% purity. Sodium silicate treated soil inhibited plant growth promoting rhizobacteria in contrast to nanosilica and other bulk sources. Surface property and effect of soil nutrient content of nanosilica treatment were improved. Colony forming unit (CFU) was doubled in the presence of nanosilica from 4 × 105 CFU (control) to 8 × 105 CFU per gram of soil. The silica and protein content of bacterial biomass clearly showed an increase in uptake of silica with an increase in nanosilica concentration. Nanosilica promoted seed germination percentage (100%) in maize than conventional Si sources. These studies show that nanosilica has favourable effect on beneficial bacterial population and nutrient value of soil.

Electrospun MgO/Nylon 6 Hybrid Nanofibers for Protective Clothing

Magnesia (MgO) nanoparticles were produced from magnesite ore (MgCO3) using ball mill. The crystalline size, morphology and specific SSA were characterized by X-ray diffraction analysis, transmission electron microscopy and Brunauer-Emmett-Teller method, respectively. MgO nanoparticle-incorporated nylon 6 solutions were electrospun to produce nanofiber mats. Surface morphology and internal structure of the prepared hybrid nanofiber mats were examined by scanning electron microscopy and high-resolution transmission electron microscopy, respectively. The fire retardancy and antibacterial activity (Staphylococcus aureus and Escherichia coli) of coated fabrics made from MgO/nylon 6 hybrid nanofiber are better than those from nylon 6 nanofiber.

Application of silica nanoparticles in maize to enhance fungal resistance

In this study, maize treated with nanosilica (20-40 nm) is screened for resistance against phytopathogens such as Fusarium oxysporum and Aspergillus niger and compared with that of bulk silica. The resistivity is measured for disease index and expression of plant responsive compounds such as total phenols, phenylalanine ammonia lyase, peroxidase and polyphenol oxidase. The results indicate that nanosilica-treated plant shows a higher expression of phenolic compounds (2056 and 743 mg/ml) and a lower expression of stress-responsive enzymes against both the fungi. Maize expresses more resistance to Aspergillus spp., than Fusarium spp. These results show significantly higher resistance in maize treated with nanosilica than with bulk, especially at 10 and 15 kg/ha. In addition, hydrophobic potential and silica accumulation percentage of nanosilica treated maize (86.18° and 19.14%) are higher than bulk silica treatment. Hence, silica nanoparticles can be used as an alternative potent antifungal agent against phytopathogens.

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.

Nanohydroxyapatite-chitosan-gelatin polyelectrolyte complex with enhanced mechanical and bioactivity

A wet chemical approach was used to synthesis HAp-chitosan-gelatin nanocomposites at different wt.% of chitosan-gelatin (CG) ratios such as CG-00, CG-40, CG-31, CG-22, CG-13 and CG-04. XRD analysis confirms the formation of HAp on nanocomposite matrix and the decreased crystallite size was found with the decrease in chitosan and increase in gelatin compositions. FTIR study reveals that the presence of characteristic bands of HAp and CG. The decrease in chitosan in CG leads to band shift of organic phase towards a higher wave number side due to the intimate bonding with an inorganic phase. FE-SEM images show that the particles had a short nanorod-like morphology. The bioresorbability and microhardness test indicate that the composites have better resorbability and hardness than pure HAp. It was inferred that particle size, morphology, resorbability and hardness of the composite can be altered by tuning the composition.

Screening of in vitro cytotoxicity, antioxidant potential and bioactivity of nano- and micro-ZrO2 and -TiO2 particles

Nanometal oxides are used in tissue engineering and implants. The increased use of nanoparticles suggests the need to study their adverse effects on biological systems. The present investigation explores in vitro cytotoxicity, antioxidant potential, and bioactivity of nano- and micro-particles such as zirconia (ZrO2) and titania (TiO2) on biological systems such as National Institute of Health (NIH) 3T3 mouse embryonic fibroblasts cell line, di(phenyl)-(2,4,6-trinitrophenyl) iminoazanium (DPPH) and simulated body fluid (SBF). The cell line viability % indicated that nano ZrO2 and TiO2 were less toxic than microparticles up to 200µgml(-1). DPPH assay revealed that the free radical scavenging potential of tested particles were higher for nano ZrO2 (76.9%) and nano TiO2 (73.3%) at 100mg than that for micron size particles. Calcium deposition percentage of micro- and nano-ZrO2 particles, after SBF study, showed 0.066% and 0.094% respectively, whereas for micro- and nano-TiO2, it was 0.251% and 0.615% respectively. FTIR results showed a good bioactivity through hydroxyapatite formation. The present investigation clearly shows that nanoparticles possess good antioxidant potential and better biocompatibility under in vitro conditions which are dose and size dependent. Hence, cytotoxicity itself is not promising evaluation method for toxicity rather than particles individual characterisation using antioxidant and bioactivity analysis.

Synthesis and characterisation of polymeric nanofibers poly (vinyl alcohol) and poly (vinyl alcohol)/silica using indigenous electrospinning set up

Indigenous design and fabrication horizontal of electrospinning set up was developed to facilitate with double drum conveyor belt system to make ease in harvesting nanofibers rapidly. As a bench mark study, organic-inorganic nanofiber composite was synthesised employing our indigenous electrospinning set up. The aqueous solution of poly (vinyl alcohol) and poly (vinyl alcohol)/silica sol were employed to produce nanofiber mats in order to vary the experimental parameters such as voltage, solvent effect and the effect of catalyst. The synthesised pure electro spun poly (vinyl alcohol) and poly (vinyl alcohol)/silica sol fibers were characterized by Scanning electron microscopy (SEM), Atomic force microscopy (AFM) and Fourier transform infra red spectroscopy (FTIR). According to the results, the fine polymeric nanofibers were achieved in the size range of 100-500 nm for pure poly (vinyl alcohol) fiber and 100-700 nm for polyvinyl alcohol/silica and the constitution of silica in rendering better fiber mats with this double drum set up.

Effect of contact angle, zeta potential and particles size on the in vitro studies of Al2O3 and SiO2 nanoparticles.

Currently, nanometal oxides find their role in different biological applications such as tissue engineering, implant and bone replacement materials. Owing to the increased use of nanoparticles, it is necessary to understand their release and toxicity in the biological system. In this regard, three independent studies such as in vitro cytotoxicity, antioxidant activity and biocompatibility of nano- and micrometal oxide particles such as alumina (Al2O3) and silica (SiO2) are evaluated. It is evident from cell viability study that nanoAl2O3 and SiO2 particles are less toxic when compared with microAl2O3 and SiO2 to NIH 3T3 cell lines up to 200 µg/ml. Antioxidant properties of micro- and nanoAl2O3 in terms of radical scavenging percentage for micro- and nanoAl2O3 are 59.1% and 72.1%, respectively, at 100 mg. Similarly, the radical scavenging percentage of nano- and bulk SiO2 are 81.0% and 67.2%, respectively. The present study reveals that the cellular behaviour, interaction and biocompatibility of metal oxides differ with dose, particle size, contact angle and zeta potential. The present study opens up a new strategy to analyse in vitro nanotoxicity.