Ag/ZnO nanocomposites were synthesized by a rapid one-step microwave-assisted combustion
method. The as-synthesized samples were characterized by X-ray diffraction, scanning electron
microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence
and ultraviolet–visible spectrophotometry. XRD results showed that hexagonal ZnO and cubic Ag were
obtained. Ag nanoparticles were chemically attached on the surface of ZnO. The decrease in the energy
band gap of Ag/ZnO nanocomposites and the photoluminescence quenching were observed while the
Ag content was increased. Furthermore, the introduction of Ag nanoparticles leads to significantly
improved photocatalytic activities in the case of ultraviolet irradiation, but in the case of visible-light
irradiation opposite results were obtained. The corresponding mechanism was discussed in detail.