PH-Controlled interfacial assembly and disassembly of highly luminescent blue emitting Zn_xCd_1-xS/dodecylamine complexes

We present a robust strategy for assembling and disassembling of highly luminescent blue emitting Zn_xCd_1-xS/dodecylamine (DDA) complexes via a facile water/chloroform interface. Firstly, thioglycolic acid (TGA)-stabilized ternary Zn_xCd_1-xS nanocrystals (NCs) were synthesized in aqueous solution. And then, relying upon the facile water/chloroform interfacial platform, such NCs are assembled into the flake-like microstructures under the direction of DDA molecules when the pH of the water phase is adjusted into an optimal acidic range. Simultaneously, the NCs are transferred from the water into the chloroform phase due to the electrostatic interactions between carboxyl groups and amino of DDA molecules. Interestingly, by reversibly adjusting the pH of the water phase into an optimal basic range, the flake-like Zn_xCd_1-xS/DDA complexes are disassembled into separate NCs and DDA, and these NCs are reversibly transferred back into the water phase. The photoluminescence (PL) quantum yield (QY) of Zn_xCd_1-xS/DDA complexes after interfacial assembly is improved to 55% from 6%. Particularly, a QY of about 22% still retains for the Zn_xCd_1-xS NCs even after the interfacial disassembly.