Crown@ZIF-67/MXene Sensor for Ultrasensitive and Selective On-Site Tl + Monitoring

Thallium (Tl) is a highly toxic priority pollutant, yet reliable monitoring remains challenging because many Tl sensors lack sufficient selectivity, portability, and durability in complex waters. A tightly coupled Crown@ZIF-67/MXene composite was assembled and integrated onto a screen-printed carbon electrode (SPCE) to create a portable electrochemical sensor for Tl + . Crown@ZIF-67/MXene was synthesized via an in situ crystallization route, in which 18-crown-6 was introduced during ZIF-67 growth so that ZIF-67 nucleated and grew around the crown ether while simultaneously anchoring onto MXene to form a tightly coupled composite. Under optimized square-wave anodic stripping voltammetry (SWASV), Crown@ZIF-67/MXene/SPCE provides a wide linear range (0.1–300 μg L –1 ) and a low limit of detection (0.036 μg L –1 ), while maintaining accurate quantification in the presence of coexisting ions (measurement error