Selective detection of mercury(II) and copper(II) based on the opposite size-dependent fluorescence quenching of CdTe quantum dots

Three different size CdTe quantum dots (QDs) capped by 3-mercaptopropionic acid (MPA) have been prepared in aqueous solutions, and their interactions with Cu2+ and Hg2+ have been investigated. The opposite size-dependent fluorescence quenching of CdTe QDs by Hg2+ and Cu2+ was observed: Hg2+ quenched smaller particles more efficiently than larger ones while larger particles were more markedly quenched by Cu2+. Based on the different size responses, Hg2+ and Cu2+ were respectively detected with high sensitivity and selectivity, for the first time, using the QDs with different sizes but the same components and capping ligands.