Utilizing Chemical Raman Enhancement: A Route for Metal Oxide Support-Based Biodetection

Raman scattering enhancement was observed in systems where different metal oxide semiconductors (TiO2, Fe2O3, ZrO2, and CeO2) were modified with enediol ligands. The intensity of Raman scattering was dependent on laser frequency and correlated with the extinction coefficient of the CT complex of the enediol ligands and nanoparticles. The mechanism of Raman enhancement was studied by varying both the chemical composition of the enediol ligand and the chemical composition (and crystal structure) of the nanoparticles. We found that the intensity of the Raman signal depends on the number of surface binding sites, electron density of the ligands, and their dipole moment. Changes in chemical composition caused variations in the intensity, frequency, and number of Raman bands observed. We also showed that Raman scattering is observed for the bioconjugated system, where a peptide is linked to the surface of the particle through a catechol linker, and further investigated the potential for such a system in the development of Raman-based in vivo and in vitro biodetection, cell labeling and imaging, and nanotherapeutic strategies.