An In Situ Oxidation Strategy for Ti₃C₂@TiO₂ Heterojunction: Narrow-Band Photodetection and Trace Chromium Ion Determination

Ti₃C₂ MXene has frequently been applied in photodetection, while there are few works directly utilizing Ti₃C₂ MXene as an active material due to the fast carrier recombination. The construction of MXene-based heterojunctions have been demonstrated to further enhance the photo-response performance. In this work, a Ti₃C₂@TiO₂ heterojunction was fabricated by an in situ oxidation approach and used to construct a photoelectrochemical photodetector. The as-fabricated photodetector exhibits a narrow-spectrum response (334–380 nm), with an optimized photocurrent density of 6.43 µA/cm² and a photoresponsivity of 5057.14 µA/W. Benefiting from interface engineering, the Ti₃C₂@TiO₂-based photodetector possesses excellent stability and sensitive response to chromium. A large range of 10⁻¹²–10⁻⁶ M could be achieved in a tea water matrix with an ultra-low detection limit of 7.6 × 10⁻¹² M. We anticipate that this study will provide an effective approach for the design of MXene-based photodetectors and pave the way for online chromium monitoring sensors in particular.