Synthesis and room temperature photoluminescence of AgI nanoparticles embedded in silica sol–gel coating

AgI nanoparticles embedded in sol–gel silica coating were synthesized by a soaking–heating method. X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), optical reflection, and photoluminescence (PL) measurements were used to characterize the coating. The size of the AgI particles was about 10–40 nm. A red shift of ∼10 nm on the absorption edge as well as the formation of a band tail was observed. The PL spectrum of the coating exhibits main emissions at 333, 370, 435, 470, and 510 nm. The former two corresponding to nonbridging oxygen hole centers (NBOHC) and E′ centers in silica, respectively. The emission at 435 nm is ascribed to radiative excitonic recombination of AgI, while the 470-nm one is associated with a transition between the tail of the conduction band (CB) and the valence band (VB). The emission at 510 nm may arise from free Ag+ ions or defects.