Study of size dependent photo-induced exciton life-time and photocatalytic activity of nanocrystalline CdZnS

Abstract

CdZnS nanoparticles with variable size within the range of 2–13 nm have been synthesized using the chemical precipitation method. Size dependent exciton lifetime and photocatalytic activity has been studied in search of a novel nanophotocatalyst. X-ray diffraction (XRD) and transmission electron microscope (TEM) techniques have also been used for the structural and crystallographic studies. Phase transformation from wurtzite to cubic has been observed with decreasing average nanocrystallite size in the strong confinement regime. High-peak power pulsed N2-laser has been used as an excitation source to study the time-resolved luminescence spectra.The excited state life-time values have been calculated from the recorded multi-exponential decay curves. The photocatalytic activity of CdZnS nanocrystallites was measured, as a function of average nanocrystallite size using the methylene blue dye, as a model catalytic dye-agent. A new correlation between the excited state lifetime and photocatalytic activity is observed in nanocrystalline CdZnS in comparison to the correlations which was observed normally for the oxide-based (titania) photocatalyst systems. These studies will definitely help in the development of new type of smart nanophotocatalytic materials