Size-controlled synthesis of silver nanoparticles on Ti-containing mesoporous silica thin film and photoluminescence enhancement of rhodamine 6G dyes by surface plasmon resonance

Silver nanoparticles having a narrow size distribution were synthesized on Ti-containing mesoporous silica thin film (Ti-MSTF) using a simple photo-assisted deposition (PAD) method. Their particle sizes were successfully controlled by changing the photo-irradiation time during the deposition and average particle sizes at irradiation times of 1, 5 and 24 h were determined to be 2.7, 4.7 and 7.6 nm, respectively. The XPS depth profile analysis indicated that silver nanoparticles mainly exist not on the surface but in the thin film. UV-vis absorption spectra of these films showed an absorption band in the visible-wavelength region attributed to the surface plasmon resonance of silver nanoparticles. Rhodamine 6G (R6G) dye molecules were further embedded on Ti-MSTF after silver nanoparticle deposition. Photoluminescence properties of R6G dyes on these thin films were enhanced due to surface plasmon excitation from silver nanoparticles and the photoluminescence intensity reached up to 3 times as high as that achieved without silver nanoparticles. It was proven that the silver nanoparticle size had a strong influence on these enhancement effects.