Interstitial sulfur photoluminescence in thermochemically synthesized CdS nanocrystals (NCs)

¹ Physics Department, Tarbiat Modares University, Tehran, Islamic Republic of Iran
² Physics Department, Arak University, Arak, Islamic Republic of Iran
³ Physics Department, Sharif University of Technology, Tehran, Islamic Republic of Iran

^a e-mail: saievare@modares.ac.ir

Received: 27 December 2010
Revised: 21 May 2011
Accepted: 27 June 2011
Published online: 28 September 2011

Abstract

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