Purine(s)-capped Q-CdS nanoparticles have been employed as photosensitizers to perform the reaction of tryptophol. Tryptophol replaces the purine in the outer shell of purine(s)-capped Q-CdS having core/shell structure. Its presence does not bring any noticeable change in its optical property but quenches the fluorescence and reduces the fluorescence lifetime significantly. The dynamics of the charge carries and their reactivity are related to the binding characteristics of purine to Cd2+ of CdS. The visible irradiation of the oxygenated system(s) in aqueous medium at room temperature results in the oxidation of tryptophol to form 3-hydroxyindoline and 1-(2-aminophenyl)-3-hydroxypropan-1-one as the products of the reaction. The participation of singlet 02 in the reaction scheme is ruled out. The maximum photodecomposition of tryptophol and the formation of product(s) takes place in case of purine-capped Q-CdS system (phi(-tryp) = 0.5) and the minimum yield was observed in case of adenine-capped Q-CdS system (phi(-tryp) = 0.1). The difference between the reactivity of the two has been attributed to the difference in the nature of the capping agent. (C) 2004 Elsevier B.V. All rights reserved.