Narayanasamy Kannan

High-purity nano silica powder from rice husk using a simple chemical method

A highly pure, small particle-sized and high surface area nano silica powder was prepared from rice husk using alkali extraction, followed by an acid precipitation method. The composition, phase, morphology, size and surface area of the as-synthesised nano silica powder was investigated by energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, particle size analyser and BET surface area analyser. High-purity nano silica powder was obtained by sodium hydroxide (NaOH) purification treatment (0.5, 1, 1.5, 2 and 2.5 N). The high purity of silica (∼99.9%) was obtained at 2.5 N NaOH treatment. The pure nano silica powder that is obtained shows an average particle size of ∼25 nm with a high-specific surface area (SSA) of 274 m2 g−1, with an average pore diameter of 1.46 nm.

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.

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.

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.

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 ZrO2, SiO2, Al2O3 and TiO2 nanoparticles on maize seed germination under different growth conditions

The focus of this investigation is to evaluate the phytotoxicity of selected metal oxide nanoparticles and microparticles as a function of maize seed germination and root elongation under different growth conditions (Petri plate, cotton and soil). The results of seed germination and root elongation experiments reveal that all the growth conditions show almost similar results. Alumina (Al2O3) and titania (TiO2) nanoparticles significantly reduce the germination percentage, whereas silica (SiO2) nanoparticles and microparticles enhance the same. The results of nanoparticles and microparticles of zirconia (ZrO2) are found to be same as those of controls. Root elongation is enhanced by SiO2 nanoparticles and microparticles treatment, whereas inhibition is observed with Al2O3 and TiO2 nanoparticles and microparticles. The X-ray fluorescence spectrometry data of the treated and control seed samples show that seeds uptake SiO2 particles to a greater extent followed by TiO2, Al2O3 and ZrO2. In addition, the uptake of nanoparticles is found to be greater than that of microparticles. Thus, the tested metal oxides penetrated seeds at the nanoscale as compared with the microscale. This study clarifies phytotoxicity of nanoparticles treated in different growth substrates and highlights the impact of nanoparticles on environment and agricultural systems.

Influence of Nano Nutrients on Heterocyst-Forming Cyanobacterium Anabaena ambigua Rao

The present study is deals with the influence of nanoparticles on the growth of heterocyst-forming cyanobacterium Anabaena ambigua Rao [A100]. The nano molybdenum and iron particles have been synthesized respectively from molybdenum trioxide (MoO3) and iron chloride (FeCl3) employing sodium borohydride (NaBH4) as a reducing agent and characterized comprehensively. BG11 (N−) media containing micronutrients like molybdenum and iron were replaced respectively by different concentrations of nano molybdenum [BG11 (N−Mo− + nano Mo)] (0, 5, 10, 15, 20, 25, 40, 60, 80, and 100%) and nano iron [BG11 (N−Fe− + nano Fe)] (0, 0.1, 0.2, 0.3, 0.4, 0.5, 1, 2, 3, 4, 5, 10, 15, 20, 25, 40, 60, 80, and 100%) particles for the cultivation. The effect of nano nutrients on cyanobacterial growth parameters like heterocyst formation, chlorophyll content, and protein content was analyzed. The obtained results showed that the high concentrations of nano molybdenum induce heterocyst formation, increase protein content, and decrease chlorophyll content when compared to the control, whereas the nano iron suppresses the growth of cyanobacteria Anabaena ambigua Rao [A 100].

A New Approach to Preparing Crystalline Nano Molybdenum Particles

Simple and cost-effective new method is developed to synthesize crystalline nano molybdenum particles from molybdenum trioxide (MoO3) using sodium borohydride (NaBH4) as a reducing agent. Nano molybdenum particles were studied using comprehensive characterisation. Crystallite size of prepared nano molybdenum was in the range of 24–35 nm. Particle size of nano molybdenum was around 100 nm whereas its surface area was in the range of 3.13–3.24 m2 g−1. The observed results are compared with existing results and the solid-phase technique in a muffle furnace was simple, rapid, reliable, reproducible, and cost effective in comparison with the currently available conventional methods.