Hetero-junctions prepared by deposition of unsubstituted Zn(II) phthalocyanines (Zn(II)Pc) onto a film of colloidal ZnO nanocrystals, were studied. Photoelectrochemical measurements were performed on the sensitized nanocrystalline ZnO films deposited onto optically transparent electrodes, to characterize the photoactivity of the heterojunction. A comparison between ZnO nanocrystals prepared by using a hydrolytic and non-hydrolytic route was performed in order to investigate the effect of nanocrystal surface chemistry on the photoelectrical response. The photoactivity was found to be significantly enhanced when non-hydrolytically prepared nanocrystals were used to form the heterojunction. (c) 2004 Elsevier B.V. All rights reserved.