The effect of additives on the photostability of semiconductor nanoparticles was studied using CdSe, CdSe/ZnSe and CdSe/ZnS particles of various sizes and composition. The additives included phosphine oxides, amines, and antioxidants. Strong initial enhancement of band edge emission by hexadecylamine was observed for the uncoated particles but stability over a week period in light and air was shown to be poor. Inorganic coatings rendered the nanoparticles initially insensitive to additive but provided little extra stability in terms of photoluminescence. Antioxidant was shown to be effective at reducing the rate of photooxidative degradation for all particles in chloroform but not in toluene. (c) 2005 Elsevier Inc. All rights reserved.