Label-Free, Fast Response, and Simply Operated Silver Ion Detection with a Ti₃C₂T MXene Field-Effect Transistor

Silver (Ag) is a widely used heavy metal, and its oxidation state (Ag⁺) causes serious harm to organisms after bioaccumulation and biomagnification, posing urgent demand for the rapid, efficient, and simply operated Ag⁺ detection techniques. In this work, a fast, portable, and label-free Ag⁺ detection sensor based on a Ti₃C₂T MXene field-effect transistor (FET) is reported. The Ti₃C₂T MXene works as the sensing element in the FET sensor, which shows excellent sensing performance, i.e., fast response (few seconds) and good sensitivity and selectivity to Ag⁺ without any detection label or probe. Utilizing the visual photograph, transmission electron microscopy image, and Ag elemental mapping analysis, the sensing mechanism of the label-free Ti₃C₂T MXene FET sensor is demonstrated to be the in situ reduction of Ag⁺ and the formation of Ag nanoparticles (AgNPs). Moreover, Ag⁺ detection in real samples shows that the proposed FET devices have satisfactory sensing capability for Ag⁺ in tap water and river water. This study puts forward a novel FET strategy for Ag⁺ detection in aqueous systems, which is of essential and inspiring meaning for motivating the potential applications of MXene-based sensor devices in analytical applications and the realization of on-site environmental monitoring.