High Anti-Interference Ti₃C₂T_x MXene Field-Effect-Transistor-Based Alkali Indicator

MXenes, a group of emerging two-dimensional (2D) transition metal carbides or nitrides, have attracted wide interest due to their unique structures and properties. Their stability and applicability in different media especially in an alkaline environment are directly associated with their potential applications and are not yet explored. Herein, a field-effect transistor (FET) is fabricated with single/double-layer Ti₃C₂T_x MXene. The Ti₃C₂T_x FET indicator shows a fast (∼1 s), sensitive, and selective response to alkali. Moreover, the device can work even in a high-salinity (2 M NaCl) environment, suggesting its high anti-interference ability for alkali in a high-ionic-strength environment. Using an in situ morphological image evolution study, it is demonstrated that the response signal results from alkali-induced denaturation of Ti₃C₂T_x nanosheets. The Ti₃C₂T_x-based alkali FET indicator and systematic evaluation on alkali-induced structure evolution of Ti₃C₂T_x provide essential insights into MXene-based FETs and future applications of MXene in alkaline environments.