Phase tunable synthesis of Cu2–xS nanocrystals and their cation substitution reactions

Cation substitution (CS) reactions utilization of Cu_2–xS nanocrystals (NCs) have been emerged as a powerful postsynthetic method to produce complicated nanostructures and metastable phases. For these CS reactions, it is of great importance to tune the crystal phase of the Cu_2–xS NCs since it strongly affects the reaction kinetics, thermodynamics, reaction intermediates, and final products. Herein, hexagonal phase djurleite Cu_1.94S NCs and cubic phase digenite Cu_1.8S NCs were synthesized by simple tuning of the amount of thiourea (TU). In particular, 0.5 mmol of TU is responsible for the formation of the djurleite Cu_1.94S NCs, while 5.0 mmol of TU is responsible for the formation of the digenite Cu_1.8S NCs. Afterward, the Cu_1.94S and digenite Cu_1.8S NCs were substituted by Zn²⁺ and Cd²⁺, and hexagonal phase wurtzite ZnS and CdS NCs, cubic phase zincblende ZnS and CdS NCs were produced. These ZnS and CdS NCs are otherwise difficult to access without the CS method. Therefore, our findings in the present study provide a straightforward phase tuning of the Cu_2–xS NCs, and potential guidelines for creating more complicated metal sulfide nano(hetero)structures.