Sarvari Khatoon

Structural characterization and antimicrobial properties of silver nanoparticles prepared by inverse microemulsion method

Silver nanoparticles have been synthesized in the inverse microemulsions formed using three different surfactants viz., cetyl-trimethyl ammonium bromide (CTAB), Tergitol and Triton X-100. We have done a systematic study of the effect of the surfactants on the particle size and properties of the silver nanoparticles. Microscopic studies show the formation of spheres, cubes and discs shaped silver nanostructures with the size in the range from 8 to 40 nm. Surface plasmon resonance (SPR) peak was observed around 400 nm and 500 nm. In addition to SPR some extra peaks have also been observed due to the formation of silver metal clusters. The surface area increases from 3.45 to 15.06 m(2)/g with decreasing the size of silver nanoparticles (40-8 nm). To investigate the antimicrobial activity of silver nanoparticles, the nanoparticles were tested against the yeast, Candida albicans and the bacterium, E. coli. The results suggest very good antimicrobial activity of the silver nanoparticles against the test microbes. The mode of action of the antimicrobial activity was also proposed.

A Review on Chemical Synthesis, Characterization and Optical Properties of Nanocrystalline Transition Metal Doped Dilute Magnetic Semiconductors

Nanomaterials have fascinated researchers in recent years because these materials exhibit unusual optical, magnetic and electrical properties as compared to their bulk counterparts. Incorporating impurity ions into a semiconducting host to extend its properties has been one of the most important techniques that paved the way for the modern technology based on spintronic devices. Over the past few years, oxide based dilute magnetic semiconductors (DMSs) have gained remarkable interest due to the possibility of inducing room temperature ferromagnetism. This review describes the experimental developments and optical properties of oxide based DMSs, including the recent results on ZnO, CdO and In2O3 based systems. Optical properties of transition metal (TM)-doped ZnO, CdO and In2O3 dilute magnetic semiconductor nanoparticles show red shift in energy band gaps. Such types of phenomena are attributed to sp-d exchange interactions between band electrons and localized d-electrons of the substituted transition metal ions. Table of Contents

Chemistry of reverse micelles: a versatile route to the synthesis of nanorods and nanoparticles

Nanostructured wires and rods are expected to have interesting optical, electrical, magnetic and mechanical properties as compared to micron sized whiskers and fibers. We have explored a versatile route for the synthesis of nanorods of transition metal (Cu, Ni, Mn, Zn, Co and Fe) oxalates, succinates of few metals (Co and Fe) and SnO2 nanoparticles using reverse micelles. The aspect ratio of the nanorods copper oxalate could be modified by changing the solvent. The aspect ratio of the cobalt oxalate nanorods could be modified by controlling the temperature. The nanorods of metal (Cu, Ni, Mn, Zn, Co and Fe) oxalates were found to be suitable precursors to obtain a variety of transition metal oxide nanoparticles. Our studies show that the grain size of CuO nanoparticles is highly dependent on the nature of non-polar solvent used to initially synthesize the oxalate rods. All the commonly known manganese oxides could be obtained as single phases from the manganese oxalate precursor by decomposing in different atmosphere (air, vaccum or nitrogen). In order to see the templating effect of the ligand we have changed the dicarboxylate ligand by using succinate (4 carbon chain) instead of oxalate (2 carbon chain).We found spherical nanoparticles for iron succinate where the oxidation state of Fe is in +3. Shorter rods of cobalt succinate were observed. Monophasic tin dioxide (SnO2) nanoparticles with an average size of 6-8 nm was obtained at 500°C by the reverse micellar route using liquor NH3 as precipitating agent.