Influence of the incorporation of metals on the optical properties of MCM-41

We studied the optical properties of mesoporous aluminosilica incorporated with metal nanoparticles, which can be used to efficiently enhance catalytic activity for CO oxidation. Analysis of the PL spectra indicated that the incorporation of Al greatly enhanced the generation of oxygen related defects. When Au nanoparticles were deposited onto Al-MCM-41, both the PL and PLE spectra suggested that the metal nanoparticles were strongly attracted by the electrostatic force induced by the charged oxygen defects. Electron spin resonance measurement provided further evidence, registering a spike in the O2- intensity following incorporation of the metal particles, as the strong interaction between the F+ center and the metal particles induced electron transfer to the trapped O2 molecule. These discoveries shed further light on the perplexing mechanism by which the Si/Al ratio and metal particles can give rise to dramatic enhancement of the catalytic activity for CO oxidation.