Single-step synthesis of hyperbranched, luminescent Mn2+-doped ZnSe1-XSx nanocrystals using dichalcogenide precursors

Abstract

Taking advantage of dichalcogenide precursors, a simple, single-step heat-up method for obtaining Mn2+-doped ZnSe1-xSx nanocrystals (NCs) is presented. Tuning the ratios of diselendide and disulfide precursors results in alloys with varying shape, size and composition. When diphenyldiselenide (Ph2Se2) is used, highly branched networks of small NCs form. Dimethydisulfide (Me2S2) induces formation of larger NCs with less branching. Mixtures of the two exhibit branching proportional to the amount of Ph2Se2vs. Me2S2, allowing formation of a series of branched Mn2+-doped NCs. Interestingly, these NCs exhibit photoluminescence (PL) characteristic of Mn2+, despite the large number of defects and unusual shapes they possess. This demonstrates Mn2+ can be successfully doped into NCs with several degrees of branching, in which it acts as an efficient radiative trap. Addition of thiol to the NCs led to a large enhancement in the Mn2+ PL. In organic solution, the sensitivity to thiol varied with the degree of NC branching, with hyperbranching NCs giving the most sensitive response. After transfer to aqueous solution, the Mn2+ PL of the hyperbranched NCs increased dramatically in response to μM concentrations of dithiothreitol (DTT).