Microwave-assisted sonochemical synthesis of Cu and Mn doped GSH–ZnS polypeptide quantum dots and their enhanced photoelectrochemical properties

Abstract

A series of Cu and Mn doped glutathione (GSH)–ZnS polypeptide quantum dots (QDs) were successfully prepared by a facile one-pot microwave-assisted sonochemical synthesis approach. Herein, GSH acted as a sulfide source and dispersant, as well as a reducing agent to form polypeptide QDs. The products were characterized by high-resolution transmission electron microscope (HRTEM) and energy dispersive spectroscopy (EDS). Results show that the size of the polypeptides QDs was 2–3 nm. In Fourier transform infrared (FT-IR) spectra, the splitting of S–H bonds and substitution by S–Zn can be noticed. The bonding interaction between Cu, Mn and Zn ions toward S was further confirmed from X-ray photoelectron spectroscopy (XPS) analysis. The results confirmed the partial Cu(Mn) substitution of Zn. Fluorescence (FL) spectra and UV-vis absorption spectra were used to investigate the optical properties. It was found that the doping of Cu and Mn could decrease the band gap of GSH–ZnS from 3.67 eV to 2.86 eV. The photoelectrochemical (PEC) properties of GSH–ZnS were enhanced due to the doping of Cu and Mn which has excellent chemical stability. The possible photoelectrochemical reaction mechanism is discussed.