The influence of cysteamine and counterion concentrations on the properties of CdSe/ZnS quantum dots

Abstract

The influence of the cysteamine surfactant concentration on the stability of CdSe/ZnS nanoparticles (NPs) solubilized by this compound at the phase interface between two immiscible liquids is considered. The steady-state and time-resolved fluorescence spectroscopy data show that the fluorescence quantum yield of cysteamine-coated NPs and their stability to aggregation in a potassium phosphate buffer are determined by the balance between the concentrations of surfactant in the aqueous phase and hydrophobic NPs in the nonpolar phase (chloroform, toluene, etc.). It is found that the brightest and most stable hydrophilic NPs can be obtained by completely coating them by cysteamine molecules without a surfactant deficit or excess in the reaction at the phase interface.