Label-Free, Fast Response, and Simply Operated Silver Ion Detection with a TiCT 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 TiCT MXene field-effect transistor (FET) is reported. The TiCT 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 TiCT MXene FET sensor is demonstrated to be the 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.