A new aqueous chemical growth method for in situ generation of ZnO clusters inside MCM-41 without modification scheme has been developed. Different from classical methods, the host MCM-41 does not need to be surface modified. Furthermore, ZnO clusters were prepared without calcinations, which could pack in the channels of mesoporous materials to produce quantum size effects. The PL emission peak was blue shifted to 420 nm. (c) 2005 Elsevier Ltd. All rights reserved.