Intracavity stimulated-emission amplification of fluorescence quenching for ultrasensitive Cd2+ detection in a single nanowire laser

Micro/nano lasers offer a promising alternative to fluorescent probes for sensing applications. Semiconductor nanowires (NWs) can naturally serve as laser cavities, enabling enhanced light–matter interaction at the single-NW level. However, most reported NW lasers rely on environmental refractive-index changes, which are not applicable to heavy metal ion detection dominated by quenching. Here, we propose a lasing-based sensing mechanism in single NWs toward ultrasensitive heavy metal ion detection and experimentally demonstrate it using Cd2+ as a proof-of-concept target. Through a modified lasing rate-equation model, we elucidate the intracavity stimulated-emission amplification for quenching-induced perturbations, supported by experimental validation including the light in–light out curves, threshold variations, and fluorescence lifetime measurements. Ultrasensitive Cd2+ detection is experimentally demonstrated with a lowest tested concentration of 25 pg/ml. As a general performance benchmark, this value is approximately 9.8-fold to three orders of magnitude lower than those reported for conventional fluorescence methods. These results may extend the application of single NW lasers toward a compact platform for quenching-based sensing.