Optical Properties of Host(SBA-15)-guest(AgI) Composite Materials

Nanoclusters AgI have been prepared in the channels of SBA-15 molecular sieve host, and the host-guest nanocomposite materials were prepared by a heat diffusion method. The (SBA-15)-AgI host-guest nanocomposites were characterized by powder X-ray diffraction analysis, nitrogen adsorption-desorption isotherms at 77 K, and solid-state diffuse reflectance absorption spectra. The decrease in surface area, pore diameter, and pore volume showed the existence of silver iodide clusters in the channels of SBA-15 host. X-ray diffraction illustrates that the framework of the SBA-15 remained in the host-guest composites of (SBA-15)-AgI. As the guest loading decreases, a blue-shift was observed in the diffuse reflectance spectra. This shows that the guest existed in the channels of SBA-15 and a quantum confinement effect emerged. The photoluminescence (PL) spectra show that the PL at ~2.38 eV, associated with the hydrogen-related species, decreases substantially after the loading of AgI in SBA-15. The decrease of the PL indicates the reduction of the
hydrogen concentration on the pore surface of SBA-15 after the loading of AgI guest. The intensity decrease of the self-trapped exciton (STE) band at 2.76 eV also suggests a hindrance for generating the excitons upon adding the AgI guest into the SBA-15 host.