Rangaraj Suriyaprabha

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.

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.

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.

Larvicidal, super hydrophobic and antibacterial properties of herbal nanoparticles from Acalypha indica for biomedical applications

The present study is aimed at developing a biocompatible nanomaterial with excellent medicinal properties using herbs. The herbal nanoparticles were prepared from shade dried leaves of Acalypha indica using the ball-milling technique. The prepared nanoparticles were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, particle size analysis, scanning electron microscopy, X-ray fluorescence spectroscopy and transmission electron microscopy. The amorphous herbal AINPs posses an average particle size distribution of 54 ± 3 nm and a UV-absorption maximum at 434 nm, and are superhydrophobic (151°) in nature. The prepared herbal AINPs were tested for their antimicrobial properties against Staphylococcus aureus and Escherichia coli. Mosquito repellent properties were investigated against three disease vectors, namely, Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus, and showed significant larvicidal activity due to the existence of phytochemical compounds in the herbal nanoparticles. The acute toxicity of the herbal nanoparticles was tested with an in vivo animal model, zebrafish (Danio rerio), to ensure biocompatibility. The observed results confirmed that herbal AINPs play a dominant role in enhancing the medicinal properties for different biomedical applications.

Foliar Application of Silica Nanoparticles on the Phytochemical Responses of Maize (Zea mays L.) and Its Toxicological Behavior

The study aimed to explore the effect of high surface (360.85 m2 g–1) silica nanoparticles (20–40 nm) on phytochemical responses during maize growth in comparison with bulk silica at 15 g L–1. The maize responses are analyzed for the changes in biochemical components. The expression of organic compounds and silica contents favored to nanosilica treatment than bulk and control. In addition, nanosilica is biologically inert against MG-63 cell line till 125 μg mL–1. Soil amendment is found better than foliar application to maize. This helps to improve sustainable farming as an alternative source of silica fertilizer for food crops.

Influence of ball milling on the particle size and antimicrobial properties of Tridax procumbens leaf nanoparticles

The herbal nanoparticles were prepared from shade dried Tridax procumbens plant leaves employing ball milling technique using different process parameters, like ball ratio/size and milling time. The obtained nanoparticles were comprehensively characterised using X-ray diffraction, Fourier transform infrared spectroscopy, UV-visible spectroscopy, dynamic light scattering, scanning electron microscopy and antimicrobial analysis techniques. The crystallinity of the nanoparticles was retained without altering even though the particle size changes due to milling periods. The antibacterial activities of the prepared herbal nanoparticles against Staphylococcus aureus and Escherichia coli were explored to understand the influence of particle size on antimicrobial activities and their functional properties. The increase in ball ratio and milling time periods leads to a decrease in nanoparticle size from 114 to 45 nm which in turn increases the antimicrobial activities. The above study confirms that antimicrobial activity relies on nanoparticle size. The observed knowledge on influence of particle size on antimicrobial activities will help to optimise the production of potential herbal nanoparticles for different biomedical applications.