We report here the synthesis of self-assembled aligned hexagonal prismatic Cu doped ZnO nanoparticles in aqueous and organic medium. The average particle size was found to be in the range of 40-85 nm. Structural study revealed the existence of ZnO phase with wurtzite structure. The copper was present as oxide, situated at the core of prismatic form of wurtzite ZnO nanoparticle with clear edges and faces. The maximum hydrogen production rate achieved was 1932 mu mol h(-1) over the as synthesized Cu doped ZnO suggesting as an active photocatalyst for hydrogen sulfide decomposition under visible light irradiation. The effect of copper concentration as a dopant on the photocatalytic activity of Cu-ZnO was studied. The photocatalytic activity of Cu-ZnO synthesized in organic media was observed to be higher as compared to aqueous medium. (c) 2006 Elsevier B.V. All rights reserved.