Photoluminescence and XPS investigations of Cu2+-doped ZnS quantum dots capped with polyvinylpyrrolidone

Cu2+‐doped ZnS quantum dots were synthesized by a chemical precipitation method in water/ethanol solution. The quantum dots obtained were characterized by X‐ray diffraction, transmission electron microscopy and spectroscopy techniques including X‐ray photoelectron spectroscopy. The [S2−]/[Zn2+] ratios have an effect on the photoluminescence of both aqueous solutions and powders of Cu2+‐doped ZnS quantum dots. For aqueous samples, a green luminescence centre is observed in the spectrum of sample 1 with [S2−]/[Zn2+] = 1:2 and a blue one for sample 2 with [S2−]/[Zn2+] = 1:1. For powders, only the green emission is the main luminescence centre, and the integrated intensity in the blue emission region of sample 1 is stronger than that of sample 2. Compared with the spectrum of CuS powders, the X‐ray‐induced Auger electron spectrum of Cu L3M45M45 in ZnS quantum dots shows a unique spectral characteristic. The 3d level of the Cu2+ ion is split into two different energy levels at 334.0 and 347.2 eV, respectively.