Detailed investigation of CdS nanoparticle surfaces by high-resolution photoelectron spectroscopy

Direct and detailed information about the surface of differently sized CdS nanoparticles has been obtained from high-resolution X-ray photoelectron spectroscopy using tunable synchrotron radiation. We identify up to four distinct components in the S 2p core level spectra. Two of them are assigned to bulk and surface S-species of the nanoparticles, the latter arising from a surface core level shift due to their S-termination. The remaining S 2p components stem from S-atoms of the stabilizer thiol group bound to Cd and to S-S-bonds formed by thiol groups which are attached to surface S-atoms. In the latter case, the oxidation of the nanoparticle surface is drastically reduced. (C) 1999 Elsevier Science B.V. All rights reserved.