RESUMO
Heterostructures of gold-nanoparticle-decorated reduced-graphene-oxide (rGO)-wrapped ZnO hollow spheres (Au/rGO/ZnO) are synthesized using tetra-n-butylammonium bromide as a mediating agent. The structure of amorphous ZnO hollow spheres is found to be transformed from nanosheet- to nanoparticle-assembled hollow spheres (nPAHS) upon annealing at 500 °C. The ZnO nPAHS hybrids with Au/rGO are characterized using various techniques, including photoluminescence, steady-state absorbance, time-resolved photoluminescence, and photocatalysis. The charge-transfer time of ZnO nPAHS is found to be 87 ps, which is much shorter than that of a nanorod (128 ps), nanoparticle (150 ps), and nanowall (990 ps) due to its unique structure. The Au/rGO/ZnO hybrid shows a higher charge-transfer efficiency of 68.0% in comparison with rGO/ZnO (40.3%) and previously reported ZnO hybrids. The photocatalytic activities of the samples are evaluated by photodegrading methylene blue under black-light irradiation. The Au/rGO/ZnO exhibits excellent photocatalytic efficiency due to reduced electron-hole recombination, fast electron-transfer rate, and high charge-transfer efficiency.
RESUMO
We synthesized the hybrid structure of the graphene oxide (GO) sheet and the size-controlled ZnO nanoparticles. The ZnO quantum sizes were confirmed from UV-vis spectrophotometry and TEM results. The ZnO quantum dot exhibited a stable broad and strong photoluminescence (PL) emission which is broader with the increase of ZnO nanoparticle size. The hybrid ZnO/GO results an abrupt decrease of PL emission and the excellent photodegradation performance of methylene blue under UV-light irradiation. A considerable increase of the photodegradation rate with decreasing ZnO nanoparticle size is due to the enhancement of ZnO surface interaction and the improvement of electron transfer at the ZnO/GO interface.