Unraveling the Growth Mechanism Forming Stable γ-In2S3 and β-In2S3 Colloidal Nanoplatelets

Inorganic two-dimensional semiconductor nanostructures intrigue the scientific community because of their tunable and sparse electronic states and their high conductivity. The current work deals with colloidal nanoplatelets (NPLs) based on In2S3 compound, focusing on the growth mechanism that leads to the formation of two different phases, trigonal gamma-In2S3 and defect spinel beta-In2S3, both stabilized at room temperature and characterized by ordered metal voids. In particular, we substantiate the experimental factors (e.g., temperature, reaction duration, and surface ligands) that control the growth progress. The results indicated the formation of hexagonal NPLs of the gamma-phase at an elevated temperature and dodecagon NPLs of the gamma-phase at a lower temperature. A long-reaction duration time transformed the hexagons/dodecagons into truncated triangular shapes. Furthermore, the analysis of thermodynamic and kinetic factors indicated a phase transformation from the gamma-phase to the beta-phase. All phases were produced by a new colloidal procedure based on a single precursor. The structures created were verified by X-ray diffraction, high-resolution transmission electron microscopy analyses, and Raman measurements. Elementary optical properties were identified by absorption and emission measurements. The nanoplatelets discussed offer low toxicity and optical activity in the UV and visible spectral regimes and an option for electrical or magnetic doping, enabled by the existing voids.