S.S. Kalyan Kamal

Genotoxicity of nano- and micron-sized manganese oxide in rats after acute oral treatment.

The use of nanotechnology has led to rapid growth in various areas. Manganese oxide (MnO2) nanomaterials (NMs) are typically used for biomedical applications. However, characterizing the potential human health effects of MnO2 NMs is required before fully exploiting these materials. The aim of this study was to investigate the acute oral toxicity of MnO2 NMs and MnO2-bulk particles in female albino Wistar rats. The genotoxic effects were examined using comet, micronucleus and chromosomal aberration assays. Nanosized MnO2 (45nm) significantly (p<0.01) increased DNA damage in peripheral blood leukocytes and micronuclei and enhanced chromosomal aberrations in the bone marrow cells at 1000mg/kg bw. These findings showed that the neurotoxicity of MnO2-45nm in the brain and red blood cells, as determined through acetylcholinesterase activity, was significantly (p<0.01) inhibited at 1000 and 500mg/kg bw doses. MnO2-45nm disrupted the physicochemical state and neurological system of the animals through alterations in ATPases via the total Na(+)-K(+), Mg(2+) and Ca(2+) levels in the brain P2 fraction. In addition, 500 and 1000mg/kg bw doses of MnO2-45nm caused significant changes in AST, ALT and LDH levels in the liver, kidney and serum of treated rats. Significant tissue distribution was found in all tissues in a dose- and time-dependent manner. MnO2-45nm exhibited much higher absorptivity and tissue distribution compared with MnO2-bulk. A large fraction of MnO2-45nm was cleared in the urine and feces. The histopathological analysis revealed that MnO2-45nm caused alterations in the liver, spleen and brain. These findings will provide fundamental information regarding the potential toxicities and biodistribution of nano and bulk MnO2 generated through acute oral treatment.

Facile chemical synthesis of nano-silver powders for printable electronics applications

In this article, a simple and reproducible technique for the synthesis of silver nanoparticles in organic phase without using external reducing agents is reported. The organic phase contains silver acetate as precursor, oleic acid and oleyl amine as capping molecules and diphenyl ether as solvent. Monodispersed silver nanoparticles with an average size of 5 nm could be easily synthesised at large scale and it was possible to isolate the particles suitable for electronics applications. The formation of silver nanoparticles has been characterised in terms of optical absorption, transmission electron microscopy images and small-angle X-ray scattering. Recovered silver nanoparticles reveal X-ray diffraction of a well grown-up fcc-Ag lattice. Chemical and thermal characterisations of silver nanopowders were carried out using X-ray photoelectron spectroscopy and thermogravimetric analysis, respectively. For the latter purpose, concentrated dispersions of silver nanoparticles were prepared and used for depositing uniform thin layers. Thin films were sintered at low temperature to obtain conductive films and the films were characterised using scanning electron microscope. Electrical conductivity of the conductive films was in the range 2–3 × 104 S cm−1.

Sacrificial seed mediated synthesis of copper nanopots by a modified polyol process

A novel modified polyol process has been developed for the synthesis of hollow copper nanopots. Cobalt hydrazine complex was employed for the preparation of cobalt nanoparticles (NPs), which in turn acted as sacrificial seeds for the production of Cu nanopots and nanocups. The reduction of Cu2+ to Cu0 was observed by the colour change from bluish green to dark brownish red. The reaction was followed with the help of a UV–Vis spectrometer. A surface plasmon band at 558 nm indicated the formation of Cu NPs. Chemical characterisation was carried out using inductively coupled plasma optical emission spectrometer and Leco gas analysers, CS-444 and TC-600. Crystal structure was obtained by carrying out X-ray diffraction studies and it showed a face centred cubic structure. Particle size and morphology were obtained from scanning electron microscope. On average, copper nanopots of size 72 nm could be obtained using this method.

Effect of chemical composition and Co-core size on the magnetic and magneto-transport properties of CoyAg100−y core–shell nanocrystallites

ABSTRACT This paper describes the applicability of a modified polyol process in conjunction with a transmetallation reaction in synthesis of CoyAg100−y nanocrystallites of a core–shell structure. The substitution Co → Ag is varied as 20 ≤ y ≤ 95 by tuning the microstructure with functional magnetic and giant magneto resistance properties. The existence of core–shell structures was confirmed through transmission electron microscope and the size of Co-core increased from 8 to 50 nm with decrease in Ag-content of the sample. The magnetic behaviour of the sample changed from a pseudo-superparamagnetic nature to ferromagnetic with increase in Co-core size. Normalised saturation magnetisation values increased from 89.5 to 128.6 emu/g with increase in size of Co-core; however, none of the ferromagnetic samples exhibited any magneto resistance (MR). A value of 2.0% MR was observed in case of Co20.6Ag79.4 which increased to a maximum of 3.6% MR for Co36.6Ag63.4 sample when measured at 5 K.