Large-Size 2D β-Cu2S Nanosheets with Giant Phase Transition Temperature Lowering (120 K) Synthesized by a Novel Method of Super-Cooling Chemical-Vapor-Deposition

2D triangular β-Cu2 S nanosheets with large size and high quality are synthesized by a novel method of super-cooling chemical-vapor-deposition. The phase transition of this 2D material from β-Cu2 S to γ-Cu2 S occurs at 258 K (-15 °C), and such transition temperature is 120 K lower than that of its bulk counterpart (about 378 K).