The Composition-Dependent Photoluminescence Properties of Non-Stoichiometric ZnAgInS Nanocrystals.

A facile hot injection approach to synthesize high-quality non-stoichiometric ZnAgInS nanocrystals (NCs) in the size range of 2.8-3.1 nm was presented. The fluorescence spectra had single band gap features, and indicated the formation of alloy states rather than simple composite structures. The chemical compositions, photoluminescence (PL) emission wavelengths, and quantum yields of ZnAgInS nanocrystals were significantly influenced by the concentration of an organic capping agent. The appropriate proportion of 1-dodecanthiol in the precursor prevented the precipitation, increased the fluorescence quantum yield, and improved their optical properties. The proper ratio of capping agent allowed Zn, Ag, and In to form a better crystallinity and compositional homogeneity of ZnAgInS nanocrystals. The photoluminescence was tunable from blue to red in the range of 450-700 nm as the Ag content changed independently. The PL and absorption spectra of ZnAgInS nanocrystals showed a significant blue shift with the decrease of Ag content in the precursor. As there were no obvious differences on the average particle sizes of ZnAgInS samples, these results fully revealed the composition-dependent photoluminescence properties of ZnAgInS nanocrystals. The relative quantum yield reached 35%. The fluorescence lifetimes (τ=115-148 ns and τ=455-483 ns) were analogous to those of AgInS and (AgIn)ZnS.