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The present work describes the preliminary results on large-scale synthesis and characterisation of copper (Cu) and aluminium nitride (AlN) nano powders by transferred arc thermal plasma technique. The transferred arc was used to vaporise the precursor materials (Cu, Al metal 99.9% pure). Nano particles are formed in the gas phase as a result of homogeneous nucleation. The vapours of Al were allowed to react with NH3 gas for the synthesis of AlN. Rapid quenching using Ar/N2 then produced the desired nano powders. For the generation of Cu nano powders, argon was used as a quench gas. The resultant nano-powders of Cu, AlN were collected under the controlled atmosphere. TEM and AFM results show the particle size ranging between 70 nm and 100 nm. These particles possess exotic applications in defence systems, armour for aircraft and vehicles, aeronautical systems, power electronics, microelectronics etc.

Uncapped silver nanoparticles were synthesised using hitherto unexplored DC arc thermal plasma technique using Ar, He and mixture of Ar and He as plasma gases. Effect of change in plasma gases on the morphological properties of synthesised nanoparticles has been studied. XRD revealed formation of phase pure cubic silver. TEM study disclosed formation of nanoparticles with size in the range of 20-50 nm and 5-30 nm for silver nanopowders synthesised with He and Ar as plasma gases, respectively while a bimodal size distribution with sizes ranging from ∼20 nm to 150 nm is observed for silver nanopowders synthesised with mixture of He and Ar as plasma gases in 2 : 3 ratio. UV-visible spectroscopy results also support the wide particle size distribution. Demixing effect is presumably responsible for increase in particle size and wide variation in particle size distribution in case of nanoparticles synthesised using mixed gas plasmas.

1-D nanorod bundles as well as sea urchin and starfish like hierarchical morphological nanoarchitectures of CdS have been synthesised using a facile microwave assisted hydrothermal/semi-solvothermal technique. Observation of interesting regular/irregular pine-tree like secondary growth over these hierarchical nanoarchitectures is an important aspect of this work. Cadmium acetate and thiourea were used as precursor materials and were dissolved in solution containing mixture of diethylene triamine (DETA) and deionised water (DIW) in different volume ratios prior to subjecting the resultant solution to microwave radiation of 300 W at a reaction time of 10 min and temperature of 140°C. XRD revealed formation of hexagonal CdS with strong (002) preferred orientation (c-axis orientation). Morphology dependent optical properties are studied using room temperature photoluminescence spectroscopy. We feel such secondary growth will be highly favourable in determining the non-linear properties of optoelectronic devices fabricated using such novel hierarchical nanoarchitectures.