Theory and experiment on SERS sensitivity tuning of TiO2 aerogels based on surface oxygen vacancy engineering.

TiO 2 aerogels with high surface oxygen vacancies were fabricated by sol–gel method followed by supercritical drying. Density functional theory revealed that abundant surface oxygen vacancies endow TiO 2 aerogels with high electrostatic potential, which promotes the formation of stable surface charge transfer complexes and allows significant charge transfer from molecules to TiO 2 aerogels. [Display omitted] • TiO 2 aerogels with high surface oxygen vacancies were fabricated. • TiO 2 aerogels showed narrower band gap and higher electron density of states. • TiO 2 aerogels exhibited excellent SERS performance. • Density functional theory further revealed the SERS mechanism. The exploration of new and high-performance semiconductor substrates has always been one of the most important research directions in SERS technology. However, the low sensitivity of semiconductor SERS substrates limits their application. Herein, TiO 2 aerogels with high surface oxygen vacancies were fabricated by sol–gel method followed by supercritical drying. Compared with traditional semiconductor materials, TiO 2 aerogels exhibit low detection limits (1 × 10–7 M) for 4-mercaptobenzoic acid molecules. Moreover, density functional theory further revealed that abundant surface oxygen vacancies endow TiO 2 aerogels with high electrostatic potential, which promotes the formation of stable surface charge transfer complexes and allows significant charge transfer from molecules to TiO 2 aerogels. It is worth noting that the narrower band gap and higher electron density of states of TiO 2 aerogels effectively enhance the vibrational coupling in the substrate-molecule system, leading to significant SERS activity of TiO 2 aerogels. [ABSTRACT FROM AUTHOR]