Construction of Ultrasensitive Surface-Enhanced Raman Scattering Substates Based on TiO₂ Aerogels

Recent advances in surface-enhanced Raman scattering (SERS) on semiconductor substrates offer this technology improved selectivity on top of other advantages, such as cost efficiency. However, the enhancement factor (EF) based on the semiconductors is still low compared with the noble metal substrates. Here, a new strategy of developing the semiconductor substrates based on aerogels is proposed for the first time. According to the modified Herzberg–Teller coupling rule, TiO₂ aerogels are selected as the control object because of their large tunability. The surface area, amorphousness, and surface oxygen vacancy densities of TiO₂ aerogels are regulated synergically. Due to the tuning of band structure, including band gap and defect band, multiresonant interband charge transfer (CT) pathways are generated and enhanced CT efficiency. A strong, intrinsically activated SERS effect is generated. Amorphous TiO₂ aerogel with the highest surface oxygen vacancies shows a significant EF of 2.42 × 10⁷, and TiO₂ aerogels afford the large surface area and more active sites, which is conducive to promoting the adsorption of molecules. The aerogel-based SERS is demonstrated to have wide applicability for ultrasensitive detection of explosives and organic dyes. The aerogel nanomaterials demonstrated here open a way for the construction of low-cost and high-sensitivity SERS substrate materials.