Synthesis of Ti <sub>2</sub> CO <sub>2</sub> MXene and Its Application in Photoelectrochemical Biosensors with Ultrahigh Sensitivity and Long-Term Stability
Yang Li, Fei Cheng, Yaqin Qi, Kaiyun Chen, Jiaxin Peng, Jing Zhao, Fengqiu Jiang, Rui Xu
Abstract
Theoretical chemists have predicted that Ti 2 CO 2 is a promising semiconducting MXene with high stability and surface activity, making it suitable as the bonding layer in biosensors. However, its synthesis remains challenging due to difficulties in accurately controlling the oxidation of the initial Ti 2 C phase. Here, we successfully synthesized Ti 2 CO 2 MXene via pulsed ozone treatment (POT). The resulting Ti 2 CO 2 MXene is an n-type semiconductor with a bandgap of 0.49 eV, exhibiting a high probe adsorption capacity of ∼3.03 × 10 14 molecules/cm 2 . The successful synthesis of Ti 2 CO 2 MXene is attributed to a strategy of controlling the activation energy window during the “Ti 2 C → Ti 2 CO 2 → TiO 2 ” multistep reaction. The strong oxidizing ability of ozone reduces the activation energy barrier for the “Ti 2 C → Ti 2 CO 2 ” reaction, while precise control of short-time POT pulses inhibits the formation of TiO 2 . By employing the Ti 2 CO 2 MXene as a bonding layer in a photoelectrochemical sensor for serotonin detection, the sensor exhibits an ultrahigh sensitivity of 0.433 aM (oligomolecular level) and considerable long-term stability for over 240 h. Given its high adsorption capacity and robust long-term stability, Ti 2 CO 2 MXene becomes a positive candidate for high-precision biosensing applications.