Biennial Report 2005-2007 - Saha Institute of Nuclear Physics

146 Biennial Report 2005-07found to maximize for a Mn doping level of 2.5%.Indranil Sarkar, Milan K Sanyal, Sojiro Takeyama†SP5.1.1.5 Magnetic ordering induced spin selective energy transfer to Mn states inferromagnetic Mn doped ZnS nanoparticlesThe ferromagnetic Mn doped ZnS nanoparticles show a strong effect of magnetic ordering on PLintensity indicating magnetic ordering induced spin selective energy transfer to Mn states fromexcitonic level. The 2.5% Mn doped ZnS nanoparticles show strong quenching of PL intensitywith application of magnetic field that vanishes above the ordering temperature TC. The extent ofsuppression under magnetic field is reduced as the magnetic ordering temperature is approachedand vanishes above TC. Also the zero field PL intensity decreases as the temperature is reducedbelow TC however above it there is no such observable thermal dependence upto 60K.Indranil Sarkar, Milan K Sanyal, Sojiro Takeyama†SP5.1.1.6 Formation and ordering of gold nanoparticles at toluene-water interfaceWe performed synchrotron X-ray scattering study of formation and ordering of gold nanoparticlesat toluene-water interface through a reduction reaction. The observed X-ray reflectivity and diffusescattering data showed the formation of monolayer of ”magic clusters” at the water-toluene interface.Each cluster consisted of 13 nanoparticles with about 12Ådiameter, similar to Au-55 nanoparticles,with about 11Åorganic layer and in-plane cluster-cluster separation in this monolayercomes out to be 180ÅMonolayer of these clusters exhibited three layers of such Au nanoparticlesas a function of depth that evolve with time from a monolayer of similar particles.Milan K Sanyal, Mrinal K Bera, J Daillant†, CNR Rao†SP5.1.1.7 Vibration controlled synthesis of formation of monolayer of gold nanoparticlesat toluene-water interfaceGold nanoparticles can be prepared by reduction reaction at toluene-water interface by properchoice of chemicals. We obtained a route, by reducing mechanical vibrations, using an anti-vibrationtable a monolayer of monodisperse Au-55 gold nanoparticles at the toluene-water interface.. Westudied the time evolution of films of nanoparticles formed at the toluene-water interface both ona simple table and an anti-vibration table using tapping mode of Atomic Force Microscopy. Wefound thicker multilayer films of gold nanoparticles i.e. 12 nm in 15 minutes using the simple tablecompared to that of 2.3 nm with anti-vibration table.Mrinal K Bera, Milan K Sanyal, CNR Rao†SP