Nanosize CdS particles confined in siliceous MCM-41 channels were prepared by using reversed micelles as an insertion carrier. As-made CdS in MCM-41 host shows photoluminescence (PL) signals from both band-edge and surface defect state recombination. Calcinated CdS in the host, however, presents relatively suppressed surface defect state emission compared with band-edge emission. Such emission characteristics after calcination is ascribed to the reduced probability of recombination through deeply trapped surface defect states compared with direct excitonic recombination, which is possibly due to surface capping of the CdS nanoparticles by the host nanochannels. (C) 2002 Elsevier Science B.V. All rights reserved.