General Strategy to Prepare TiO2-Core Gold-Shell Nanoparticles as SERS-Tags

The synthesis and characterization of TiO2-based core shell nanoparticles as surface-enhanced Raman scattering (SERS) tags are reported. A hydrolysis approach is first used to generate colloidal TiO2 nanoparticles, which are subsequently tagged with Raman probe molecules and encapsulated within a gold nanoshell. The resulting core-shell nanoparticles are characterized by using a number of techniques including UV vis spectroscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy to confirm the successful coating of the Au shells. These core-shell nanoparticles exhibit very strong and reproducible SERS signals of the Raman probe molecules. Three different types of Raman probe molecules are used to prepare different SERS-active nanoparticles (SERS-tags), which demonstrate the versatility of the design. Such TiO2-based metal-coated core-shell nanoparticles will be useful as SERS-tags in biological assay and imaging applications. They may also provide a platform for fundamental studies in the ongoing investigations on the mechanisms of SERS.