Intense and stable surface-enhanced Raman scattering from Ag@mesoporous SiO2 film

A surface-enhanced Raman scattering (SERS) film consisting of mesoporous silica (MSiO2) coated Ag nanoparticles (NPs) was achieved. The as-prepared hybrid NPs were uniform in size and formed large amount of aggregates in the film. “Hot spots” were supposed to appear in the MSiO2 shells with an average size as small as 15 nm. Such a novel core-shell structure therefore induced the enhancement of SERS intensity compared to the film of bare Ag NPs and polymer film of Ag-CMC. The homogeneity and stability of SERS signals from the Ag@MSiO2 film were also tested. A relative standard deviation of SERS intensity lower than 20% from Raman mapping and a stable SERS signal with excitation power of 100 mW were observed, which were both better than the other two films. Moreover, the obtained Ag@MSiO2 film was applied to detect thiram pesticides and a detection limit as low as 1×10−8 M was reached, which indicates the advantages of the Ag@MSiO2 film in biosensor.