Controlled Preparation of Uniform TiO2-Catalyzed Silver Nanoparticle Films for Surface-Enhanced Raman Scattering

Silver nanoparticle (AgNP) film is a kind of useful material in biochemical and biomedical fields as it can be used as a sensor based on its surface plasmon resonance for surface enhanced Raman scattering (SERS) analysis. In this work, a uniform AgNP film with controlled nanoparticle size, shape, and density have been prepared on TiO2 film in a AgNO3 solution by photocatalysis reduction method. The influences of TiO2 film thickness and morphology on the AgNP's growth have been systemically studied. It is found that a thicker TiO2 film with nanocrystalline morphology leads to a higher AgNP's growth rate, while a thinner TiO2 film with membrane morphology leads to a lower AgNP's growth rate. Experimental SERS results show that the AgNP film prepared with different TiO2 films and ultraviolet light irradiation time exhibit different SERS signals of rhodamine 6G (10(-6) M). Atomic force microscope and scanning electron microscope analysis reveal that the size effect is a key factor affecting the SERS of our prepared AgNP films, which has also been evaluated by finite-difference time-domain simulation. It is found that the larger the average AgNP's size (<=lambda/4) and roughness, the higher the Raman enhancement. The SERS mapping images exhibit a good uniform Raman enhanced results in our prepared TiO(2-)catalyzed AgNP film with a low relative standard deviation of approximately 10%.