Preparation, characterization, and optical properties of host-guest nanocomposite material SBA-15/AgI

Host-guest nanocomposite SBA-15/silver iodide (Agl) was prepared by heat diffusion method. The structure, composition and optical properties of such material were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, energy disperse spectroscopy, electron paramagnetic resonance, diffuse UV-vis reflectance spectra, and photoluminescence (PL) spectra. When AgI content is below similar to 15 wt%, the guest AgI is highly dispersed on the silica channel wall, and no longer exists in the crystalline state; when AgI content exceeds this value, AgI nano-crystal can be observed. A blue shift of similar to 30 nm on the absorption edge as well as the formation of a band tail is observed. Besides, Ag clusters have been shown to exist in the composite. After the loading of guest AgI, the PL from silica at 330 nm can hardly be observed, and a novel PL emission located at 620 nm is found. The emission at 620 nm may be due to the transition process between the excited state of Ag clusters and the hole-trap state on the surface of AgI. (c) 2007 Elsevier B.V. All rights reserved.