Recent Progress in Optical Sensors Based on MXenes Quantum Dots and MXenes Nanosheets

In recent years, MXenes, as a new promising two-dimensional material, have received extensive attentions in the fields of environmental remediation, catalysts, sensors, and energy storage. To broaden the applications of MXenes in sensing, MXenes nanosheets (MNSs) and MXenes quantum dots (MQDs) are prepared by physical etching or chemical oxidation. MNSs are monolayered or multilayered MXenes nanosheets within several nanometers in height, and can serve as the perfect reaction substrate and fluorescence quencher. MQDs are spherical, fluorescent MXenes QDs within several nanometers in size, which possess favorable stability and photostability. Since the distinct features such as high conductivity, favorable hydrophilicity, biocompatibility, abundant surface functional groups, and easy functionalization, MNSs and MQDs show potential applications in the fields of anti-counterfeiting, environmental monitoring, biosensing and biomedicine. This review focuses on the research of MNSs/MQDs-based optical sensors, including colorimetric sensors, fluorescence sensors, electrochemiluminescence sensors, surface plasmon resonance sensors, and surface-enhanced Raman scattering sensors. Furthermore, the current challenges and prospects concerning MNSs/MQDs-based optical sensing techniques are discussed.