Using nanoparticulate TiO2 films, the photocatalytic growth of Ag nanoparticles (NPs) in the AgNO3 aqueous solution has been studied in terms of reduction, nucleation, and coalescence. It was proved that Ag primary particles were formed in a growth time of <1 s after the photocatalysis started. The growth dynamics was found to be critical for isotropic and anisotropic growth of Ag NPs, depending on the AgNO3 concentration and surface properties of TiO2 films. In the AgNO3 solutions of ≤300 mg/L, the isotropic growth dominates the growth dynamic behavior, producing irregularly spherical Ag NPs. In the AgNO3 solutions of ≥400 mg/L, the increased reduction rate promotes the formation of Ag nanoplates in the product. Ostwald ripening and oriented attachment were suggested to be the mechanisms dominating the isotropic and anisotropic growth, respectively. A photocatalytic growth model of Ag NPs was proposed by taking Ag atom and Ag+ ion diffusion into consideration. The plasmonic properties of the Ag–TiO2 films were studied in terms of extinction, surface enhanced Raman scattering, and fluorescence enhancement.

Molecular imaging scans cellular and molecular targets in living subjects through the introduction of imaging agents that bind to these targets and report their presence through a measurable signal. The picomolar sensitivity, signal stability, and high multiplexing capacity of Raman spectroscopy satisfies important needs within the field of molecular imaging, and several groups now utilize Raman and surface-enhanced Raman spectroscopy to image molecular targets in small animal models of human disease. This article details the role of Raman spectroscopy in molecular imaging, describes some substrates and imaging agents used in animal models, and illustrates some examples.