Synthesis of CuInS2 nanoparticles and application in the photocatalytic degradation of tetracycline

A lot of effort has been given to the development of nontoxic ternary semiconductor nanoparticles that could act as photocatalyst NIR-I (750–850 nm) or NIR-II (1000–1400 nm) optical windows. This is due to their good stability, high optical absorption coefficient, and desirable band gap that absorbs well within the solar spectrum. CuInS₂ is one of the ternary sulphide semiconductors, which has been considered to be a highly promising photocatalyst. The properties are attributed to its high optical absorption coefficient. In this study, copper indium sulphide (CuInS₂) nanoparticles were synthesized by a microwave irradiation route using copper(II) bis (N-methyl-N-ethanol dithiocarbamate) and In(III) tris (N-methyl-N-ethanol dithiocarbamate) as a precursor complexes. The copper(II) complex was varied in two different ratios (3:1 and 2:1) to determine the best synthesis regime. Then, the effect of the varying ratios on the crystalline structure, morphology, and optical properties of the CuInS₂ was studied by using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), and absorption spectroscopy. The microscopic analyses revealed that the CuInS₂ nanoparticles have similar spherical grain-like shapes whose sizes range between 10.3–50.1 nm. The increase in the concentration of copper(II) complex also altered the band gap energy, given 2.87 and 1.61 eV for CuInS₂(3:1) and CuInS₂(2:1) respectively. The photocatalytic activities of the nanoparticles were determined for the degradation of Tetracycline (TC) under visible light irradiation. The effects of process parameters such as photocatalyst dosage and initial concentration of TC were investigated to establish the optimal performance of the CuInS₂ nanoparticles. The experimental data showed a higher TC degradation percentage for CuInS₂(2:1) (95 %) compared to CuInS₂(3:1) (90 %), indicating its high potential as a photocatalyst for the degradation of TC in aqueous solution.