Glutathione-capped ZnSe and Zn1-xCdxSe alloyed quantum dots (QDs) have been successfully synthesized in aqueous solution (see figure). Their fluorescence emissions are tunable between 360 and 500 nm. The as-prepared QDs have a quantum yield of up to 50%, comparable to or better than most QDs prepared by an organometallic route. The approach can be easily scaled up for commercial production of alloyed nanocrystals of various compositions.