Composition, size and shape are three key factors that govern the optical and electrical properties of semiconductor nanostructures. 1-2 Controlling the shape of semiconductor quantum dots (QDs) is a great challenge, especially for constructing QDs without heavy metal ions such as cadmium ions, mercury ion, and so on. Herein, we have developed a reliable one-step method to synthesize Cd-free semiconductor QDs in non-aqueous solvents under high temperature (Scheme). Triangular-shape ultra-small Cu 1-x In x S 2 semiconductor QDs were obtained with near-infrared (650-900nm) emissions. The QDs were synthesized utilizing copper chloride (CuCl 2) as Cu source, indium acetate (In (OAc) 3) as In source and 1-dodecanethiol (DDT) as S source and capping ligands; the growth temperature was at 230 C. Interestingly, the QDs exhibited both size-and composition-dependent optical properties,