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.