SCIENTIFIC FOUNDATIONS OF THE INTERACTION BETWEEN As₂S₅ AND Cu(I) SALTS UNDER HYDROTHERMAL CONDITIONS: A REVIEW ARTICLE

Abstract

Copper–arsenic–sulfur-containing chalcogenides occupy an important place in inorganic chemistry and materials science owing to their semiconductor, optoelectronic, and potential photovoltaic properties. This review systematically examines the theoretical and chemical foundations of the interaction between As₂S₅ (arsenic(V) sulfide) and Cu(I) salts, particularly CuCl, under hydrothermal conditions, as well as possible phase formation pathways and characterization methods for the synthesized products, based on the existing scientific literature. Verifiable experimental publications directly addressing the As₂S₅–Cu(I) hydrothermal system are limited; therefore, findings obtained from related systems, including As₂S₅–CuCl₂, Cu–As–S phase diagrams, and solvothermal Cu(I) thioarsenates, are used solely for comparative analysis and to support hypotheses. Stable phases known in the Cu–As–S system include Cu₃AsS₄ (enargite/luzonite), Cu₁₂As₄S₁₃ (tennantite), Cu₆As₄S₉ (sinnerite), and CuAsS (lautit). Under hydrothermal conditions, temperature, pH, molar ratios, and solvent selection influence phase selectivity and morphology. X-ray diffraction (XRD), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDS), X-ray fluorescence spectroscopy (XRF), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and thermal analysis are discussed as essential methods for the reliable assessment of phase composition, chemical composition, and structure. Research gaps and potential directions for future experimental investigations are identified. The toxicity of arsenic-containing compounds is also highlighted, emphasizing the importance of laboratory safety.