Phase Control of Sulfide Nanocrystals from Thiourea-Mediated Solution

Nanomaterials that feature multiphase dictated by corresponding thermodynamic or kinetic conditions demonstrate great diversity for the exploration of novel properties like photovoltaics or thermoelectricity. To access a specific phase, especially those with a metastable nature, requires effective means to harness the determining parameters ruled by the intrinsic phase diagram. In this report, we develop a solvothermal model that is able to accurately tune the oxidation state of the metal ions in a sulfide system Cu-Sb-S, which in turn effectively regulates the phase evolution process to achieve the expected product (nanoparticles or film) in a phase pure form at a low temperature. The systematic in-situ and control investigations on different transient states illustrate the function of specific chemical groups in thiourea. Such an approach represents a general engineering method that can be readily employed in different systems, such as the Cu-Fe-S system. Furthermore, this one-pot synthetic strategy is capable of fine-tuning mix-phase sulfide nanocomposites as well. Therefore, it provides a platform to research sulfide’s phase-tunable properties, performance, and applications.