Synthesis and characterization of Zn x Hg1-x Se y S1-y quantum dots

This article describes the synthesis of highly water-soluble Zn (x) Hg1-x Se (y) S1-y quantum dots (QDs) in aqueous solution through a simple photo-assisted reaction between ZnSe QDs and mercury(I) nitrate dihydrate [Hg-2(NO3)(2)center dot 2H(2)O]. In order to deduce the optimal synthesis conditions, we varied several parameters, including the concentrations of mercaptosuccinic acid (MSA) and Hg-2(NO3)(2)center dot 2H(2)O, the illumination time, and the reaction temperature. When irradiated at temperatures below 80 A degrees C, the ZnSe QDs reacted with the S2- ions formed rapidly from MSA and the Hg2+ ions formed from Hg-2 (2+) ions to form Zn (x) Hg1-x Se (y) S1-y QDs through a process of photo-etching and surface combination. Under different conditions, we prepared a series of Zn (x) Hg1-x Se (y) S1-y QDs that emit fluorescence at the maximum wavelengths ranging from 405 to 760 nm. Inductively coupled plasma-mass spectrometry and transmission electron microscopy/energy dispersive spectrometry revealed that the content of Hg in the Zn (x) Hg1-x Se (y) S1-y QDs was greater when the synthesis was conducted at higher temperature. The Zn0.88Hg0.12Se0.44S0.56 QDs exhibit improved photostability than crude ZnSe QDs and possess long lifetimes (tau(1) similar to 38 ns and tau(2) similar to 158 ns).