Preparation and phase control of nanocrystalline silver indium sulfides via a hydrothermal route

A hydrothermal route was proposed to prepare and control nanocrystalline silver indium sulfides (orthorhombic AgInS₂, tetragonal AgInS₂, and cubic AgIn₅S₈). The reaction was carried out in an autoclave in the temperature range of 100–280 °C with AgCl, InCl₃, and thiourea as reactants. X-ray powder diffraction patterns and transmission electron microscopy images showed that the products were AgInS₂ and AgIn₅S₈ phases and well crystallized with grain diameter in the range of 20–70 nm. X-ray photoelectron spectra of the single AgIn₅S₈ phase revealed the surface stoichiometry (AgIn_5.05S_8.11), and its room temperature Raman spectrum showed a strong peak at 130 cm⁻¹ and a weak peak at around 290 cm⁻¹. The influence of reaction temperature on the phases in the final products was investigated. A possible reaction mechanism of the formation of silver indium sulfides was also briefly discussed.