Palanisamy Manivasakan

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.

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.

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.

On-line phase transition in La1− x Sr x MnO3 (0.28 ≤ x ≤ 0.36) perovskites through ultrasonic studies

La1− x Sr x MnO3 perovskite manganite materials with different compositions (x = 0.28, 0.31 and 0.36) have been prepared employing solid-state reaction technique. On-line evaluation of ultrasonic velocities and longitudinal attenuation of the above samples has been done over a wide range of temperatures using the transmission method. The observed anomalies in velocities, attenuation and elastic moduli reveal the occurrence of lattice softening and hardening near Curie temperature. The observed dramatic hardening in sound velocities and softening in attenuation are correlated with the phase transition, i.e. ferromagnetic to paramagnetic. The increase in magnitude of maximum velocity with change in Sr content at T c indicates the existence of linear magnetostriction effect. The elastic moduli study elucidates the observations made from the above-mentioned studies. The variation in the ultrasonic velocities, longitudinal attenuation and its derived parameters help us to understand the competitions between ferromagnetism and paramagnetism.

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.

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.

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.

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.

Phase transformation of ZrO2 nanoparticles produced from zircon

This article focuses on the phase transformation of zirconia (ZrO2) nanoparticles produced from zircon using a bottom-up approach. The influence of mechanical milling and thermal annealing on crystalline phase transformation of ZrO2 nanoparticles was explored. It was found that the iron oxide, as an inherent impurity present in ZrO2 nanoparticles, produced from zircon stabilises the cubic phase after calcination at 600°C. The stabilised cubic phase of ZrO2 nanoparticles was disappeared and transformed into partial tetragonal and monoclinic phases after mechanical milling. The phase transformation occurred on account of the crystal defect induced by high-energy mechanical milling. The destabilisation of cubic phase into monoclinic phase was observed after the thermal annealing of ZrO2 nanoparticles at 1000°C. The phase transitions observed are correlated to the exclusion of iron oxide from the zirconia crystal structure.