Misfortune Begets Fortune? Tailoring Facets in the MXene Oxidation Process for a Sensitive and Recyclable SERS Platform.

Liu, Xin; Sun, Yiting; Wang, Lijie; Chen, Jiahe; Zada, Amir; Isaac, Seah Hong Guan; Li, Tiehu; Dang, Alei · Nano Lett · 2026

basic_science · Level V

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Abstract

Low SERS activity and poor environmental stability of MXenes limit their potential to become universal substrates comparable to noble metals. Herein, a crystal surface engineering technique that kills two birds with one stone is proposed. By customizing the exposed surface of TiO<sub>2</sub> during the oxidation of Ti<sub>3</sub>C<sub>2</sub> MXene, the hybrid Ti<sub>3</sub>C<sub>2</sub>-TiO<sub>2</sub> substrate with a narrower bandgap and higher density of state was optimized. The stable lattice and heterostructure addressed the material's intrinsic susceptibility to oxidation (no signal drop over 180 days), while achieving a stronger charge transfer resonance effect (5.52 × 10<sup>4</sup> times higher than that of fresh Ti<sub>3</sub>C<sub>2</sub>). In addition, the Schottky barrier formed between Ti<sub>3</sub>C<sub>2</sub> and TiO<sub>2</sub> promotes the separation of photogenerated electron-hole pairs, enabling the substrate to be recycled (the degradation rate of MeB was 92.7% at 80 min). This work provides guidance for utilizing crystal facet engineering to regulate the SERS performance of substrates.