Shape and phase-controlled synthesis of specially designed 2D morphologies of L-cysteine surface capped covellite (CuS) and chalcocite (Cu₂S) with excellent photocatalytic properties in the visible spectrum

Two dimensional (2D) nanomaterials have interesting properties due to their lateral dimensions. Pure self-assembled L-cysteine stabilized covellite nanoplates (CuS@L-Cys NPs) and L-cysteine stabilized chalcocite nano leaves (Cu₂S@L-Cys NLs) were synthesized by using a template free, the facile hydrothermal route with the best control of size, phase purity structure, morphology, and electrochemical properties. Novel CuS@L-Cys NPs and Cu₂S@L-Cys NLs snowflakes dendrites were synthesized by varying synthetic parameters such as solvent, temperature (100–180 °C), reaction time (8–24 h), pH of reaction medium (7–14), the concentration of base (0.1–2.4 mL NH₃) and concentration of thiourea (1–4 mmol). By changing these factors, different morphologies such as irregular, regular, trigonal, hexagonal leaf and snowflakes dendrites like shapes were observed. CuS@L-Cys NPs and Cu₂S@L-Cys NLs were fabricated by using water and ethylenediamine (EDA) as solvent respectively. CuS@L-Cys NPs and Cu₂S@L-Cys NLs were investigated for potential photocatalytic applications in methyl orange (MO) degradation under visible light with a detailed mechanism. The noteworthy, unique bandgap of 2 eV and the special morphology of CuS@L-Cys NPs increases the active sites for adsorption of dye, which causes extraordinary degradation activity. Furthermore, the L-cysteine (L-Cys) protective layer could efficiently alleviate the photocorrosion of CuS and Cu₂S, giving rise to excellent stability.