Photo-physical Characteristics of ME-Capped CdSe Nanoprticles Syn thesized by Wet-Chemical Route

Over the last decade, semiconductor nanoparticles have attracted tremendo us interest d ue to their unique size dependent optical and electronic properties [۱,۲]. The chemical grow th of high-q uality CdSe, ZnSe, CdT e, etc. nanoparticles is now becoming a routine procedure due to the attractive features presen t in these materials [ ۳]. Here, we report a simple, saf e and economical procedure for synthesis of ca pped CdSe NPs at room temperatur e (RT~ ۲۵ ° C) via a direct reaction between Cd Cl۲ and Na۲Se in the presence of Mercaptoethanol (ME) as a cappin g agent.Results and Disc ussion : The most dramatic property of semiconductor nan oparticles i s the size evolution o f the spectroscopy analysis. The UV-vis absorption spectrum of as-prepared CdS e NPs reveals the broad and less sy mmetric exc itonic peak s at ۴۰۵ nm (Fig. ۱). Th e blue shifting of abso rption wavelength, comp ared to the bulk value (۷۱۶ nm, ۱.۷ ۳ eV), reflecting size quantization effect [۴]. Using the well known Br us equation [۱], the na noparticles diameter was estimated to be aroun d ۵±۱ nm. Absorbance wavelengt h shift and band gap v ersus ME concentration are shown in Fig. ۱ (right graph). The band gap increases from ۳.۰۲ eV (۴۱۰ nm) to ۳.۲۳ eV (۳۸۳ nm) as the conce ntration of ME capping agent increasing from ۰.۰۱ M to ۰ .۱ M. Therefore, the capping agent dependence on the band gap appears clear but small (~ ۰.۲۴ eV).