Vivek Dhand

Green synthesis of silver nanoparticles using Coffea arabica seed extract and its antibacterial activity

A novel green source was opted to synthesize silver nanoparticles using dried roasted Coffea arabica seed extract. Bio-reduction of silver was complete when the mixture (AgNO3+extract) changed its color from light to dark brown. UV-vis spectroscopy result showed maximum adsorption at 459 nm, which represents the characteristic surface plasmon resonance of nanosilver. X-ray crystal analysis showed that the silver nanoparticles are highly crystalline and exhibit a cubic, face centered lattice with characteristic (111), (200), (220) and (311) orientations. Particles exhibit spherical and ellipsoidal shaped structures as observed from TEM. Composition analysis obtained from SEM-EDXA confirmed the presence of elemental signature of silver. FTIR results recorded a downward shift of absorption bands between 800-1500 cm(-1) indicting the formation of silver nanoparticles. The mean particle size investigated using DLS was found to be in between 20-30 nm respectively. Anti-bacterial activity of silver nanoparticles on E. coli and S. aureus demonstrated diminished bacterial growth with the development of well-defined inhibition zones.

Flame synthesis of carbon nano onions using liquefied petroleum gas without catalyst.

Densely agglomerated, high specific surface area carbon nano onions with diameter of 30-40 nm have been synthesized. Liquefied petroleum gas and air mixtures produced carbon nano onions in diffusion flames without catalyst. The optimized oxidant to fuel ratio which produces carbon nano onions has been found to be 0.1 slpm/slpm. The experiment yielded 70% pure carbon nano onions with a rate of 5 g/h. X-ray diffraction, high-resolution electron microscopy and Raman spectrum reveal the densely packed sp(2) hybridized carbon with (002) semi-crystalline hexagonal graphite reflection. The carbon nano onions are thermally stable up to 600 °C.

Carbon nanotubes synthesis using diffusion and premixed flame methods: a review

In recent years, flame synthesis has absorbed a great deal of attention as a combustion methodnfor the production of metal oxide nanoparticles, carbon nanotubes, and other related carbonnnanostructures, over the existing conventional methods. Flame synthesis is an energyefficient,nscalable, cost-effective, rapid and continuous process, where flame provides thennecessary chemical species for the nucleation of carbon structures (feed stock or precursor)nand the energy for the production of carbon nanostructures. The production yield can benoptimized by altering various parameters such as fuel profile, equivalence ratio, catalystnchemistry and structure, burner configuration and residence time. In the present report, diffusionnand premixed flame synthesis methods are reviewed to develop a better understandingnof factors affecting the morphology, positioning, purity, uniformity and scalability fornthe development of carbon nanotubes along with their correlated carbonaceous derivativennanostructures.