Surface-Enhanced Raman Scattering of Phenols and Catechols by a Molecular Analogue of Titanium Dioxide.

Surface-enhanced Raman spectroscopy (SERS) of semiconducting TiO2 was used for studying binding modes and surface reactions of molecules bound at the interface but is generally limited by low signal intensity and lack of authentic structural information. Here, we report a representative titanium-oxide cluster (TOC), i.e., Ti17O24(OiC3H7)20 (Ti17), combines the benefits from both precise structures and intense SERS signals by providing a titania surface. According to the single-crystal X-ray diffraction analysis, phenols and catechols are vertically attached via σ-bonds to the certain sites of Ti17. Ti17 brings about much more intense Raman signals than the reference TiO2 NPs, leading to 10-5-10-6 M analyte detection (enhancement factors are 103-105). The contributions of focusing effect, CHEM effect and resonance mechanism, all of which are found responsible for the higher SERS activity of Ti17 than the reference TiO2 NPs, in the SERS by Ti17 are quantitatively analyzed. This study suggests SERS by TOCs may be promising for detection purposes and structural studies of environmentally and catalytically relevant molecules with fewer assumptions regarding molecular structures or binding mechanisms.