Nanocrystals were synthesized by using a thermochemical approach, with CdSO4 and Na2S2O3 as the precursors and thioglycolic acid as the capping agent. The structure and optical property of the nanocrystals were characterized by means of XRD, TEM, UV-visible optical spectroscopy and photoluminescence. The XRD and TEM analyses revealed hexagonal-phase CdS nanocrystals with an average size of around 2nm. Synthesized nanocrystals exhibited a band gap of about 3.21eV and a broad band emission from 400 to 750nm and centered at 503nm. This broad band emission was related to surface states of CdS and the results showed that the emission peak could be attributed to interstitial sulfur. The best attained photoluminescence quantum yield of the nanocrystals was about 11%. At the same conditions the photoluminescence quantum yield of thioglycolic acid capped nanocrystals was about 20 times higher than that of thioglycolic acid capped nanocrystals.

Interstitial Sulfur Photoluminescence in Thermochemically Synthesized CdS Nanocrystals (NCs). M.Molaei, E.S.Iranizad, M.Marandi, N.Taghavinia: The European Physical Journal - Applied Physics, 2011, 56[1], 10401-5