Smart and Reversible Surface Plasmon Resonance Responses to Various Atmospheres for Silver Nanoparticles Loaded in Mesoporous SiO2

The surface plasmon resonance (SPR) optical absorption of Ag nanoparticles loaded in mesoporous SiO2 (with fairly low Ag content, about 0.14 wt %) have been investigated after the nanoparticles were heated in or exposed to various atmospheres (i.e., air, H-2, water vapor, Ar, and H2S). Unexpectedly, the SPR optical absorption can completely disappear in quite a short time or intensively emerge or drastically change into semiconductor optical absorption edge. Surprisingly, the SPR switches are well reversible and very rapid when alternating treatment of samples in any two atmospheres mentioned above. In addition, those novel and distinctive SPR changes reflect a series of abnormal chemical redox behaviors in various atmospheres. The mechanisms have been discussed based on modeling multi-interactions between the mesoporous SiO2 matrix, Ag nanoparticles, and atmospheres, revealing a special surface/interface synergetic effect that induces many novel phenomena despite SiO2 usually being regarded as a chemical inert medium to noble metals and environmental atmospheres Our new findings for such a simple Ag/SiO2 system, smart, reversible, and rapid SPR responses to various atmospheres, are highly valuable for SPR gas sensor, optical switch, and other SPR optics and give a new understanding of the catalysis and surface/interface chemistry in the Ag/SiO2 system