Optical and photophysical properties of Ag/CdS nanocomposites - An analysis of relaxation kinetics of the charge carriers

Ag/CdS nanocomposites have been synthesized and characterized by TEM, XRD, electronic and fluorescence spectroscopy. The content of Ag modifies the nature of surface interaction between the two components as revealed by TEM, electronic and fluorescence measurements. Increasing contents of silver in the composite reduces the interparticle separation. The addition of silver blue shifts the absorption maxima and, influences the emission behavior and charge dynamics in a complex manner. At low molar ratio of Ag:CdS about five-fold enhancement in fluorescence is observed which is attributed to the excited state charge transfer interaction between the two components. On the contrary at high Ag the fluorescence intensity is reduced significantly to become smaller than that of pure US nanoparticles. The quenching of emission is understood to occur by the rapid electron transfer from the excited US to Ag particle. Relaxation kinetics of charge carriers of US also reveal the formation of transitory CT complex between excited US and Ag, in which the extent of electron transfer is controlled by the amount of Ag and thus supporting the steady-state findings. A mechanism of these processes is discussed. (c) 2007 Elsevier B.V. All rights reserved.