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Graphene quantum dots (GQDs) decorated Al-doped ZnS composites were prepared using the solvothermal process, and the hydrothermal method was used to prepare GQDs. Various spectroscopic techniques were used to characterize the products, and the results show that Al-ZnS attached GQD composites present lattice fringes that can be assigned to ZnS and GQDs, respectively. The absorption peaks of Al-ZnS/GQDs are red-shifted because of the doping of aluminum and the incorporation of GQDs. The luminescence intensity of Al-ZnS/GQDs shows a downward trend with the addition of GQDs. As the GQD content changes from 0.6 wt % to 1.8 wt %, the photocurrent density achieves a maximum at the addition of 1.2 wt %. The photocurrent of Al-ZnS/GQDs composites are about 700% and 200% of pure ZnS and Al-ZnS, respectively. The results indicate that Al doping can reduce the energy bandgap of ZnS and produce more photogenerated electrons. The photogenerated electrons from Al-ZnS can be extracted and transferred to GQDs, which act as conducting materials to decrease the recombination rate and improve the photogenerated electron-transfer. [ABSTRACT FROM AUTHOR]

ZnS-graphene quantum dot (GQDs) composites were synthesized by a simple solvothermal method, in which GQDs were prepared by a hydrothermal cutting process. The products were characterized by transmission electron microscopy, atomic force microscopy, X-ray diffraction and ultraviolet-visible absorption spectroscopy. The results show that GQDs were obtained by size tailoring of 1–4 graphene layers and combined with cubic ZnS nanoparticles to form ZnS-GQDs composites. The photocurrent and electrochemical behavior of the products were evaluated by transient photocurrent responses and electrochemical impedance spectra. The photocurrent density of ZnS-GQDs achieves the value of 2.32 × 10−5 A/cm2, which is 2.4-times as high as that of ZnS-graphene. GQDs serve as an electrical conducting material, which decreases the conductive path and accelerates the electron transfer. The charge-transfer resistance of ZnS-GQDs is much lower than that of ZnS-graphene and pure ZnS due to the effective electron separation and transfer ability upon the incorporation of GQDs. [ABSTRACT FROM AUTHOR]