Development of smartphone-based AIE fluorescence-quenching immunochromatographic sensors for the detection of illicit drugs in various complex sample matrices.

Illicit drug abuse poses a significant global threat to public health and social security, highlighting the urgent need for rapid, sensitive, and versatile detection technologies. To address the limitations of traditional chromatographic techniques-such as high costs and slow response times-and the drawbacks of conventional immunochromatographic sensors (ICS), including low sensitivity and non-intuitive signal outputs, a fluorescence-quenching ICS (FQICS) was developed. This sensor leverages fluorescence resonance energy transfer (FRET) between aggregation-induced emission fluorescent microspheres (AIEFMs) and gold nanoparticles (AuNPs). The ICS operates on a positive signal-readout mechanism and is integrated with a smartphone-based portable reader, enabling rapid quantitative detection of methamphetamine (MET), morphine (MOR), and ketamine (KET). Detection limits of 0.041, 0.072, and 0.059 ng mL were determined for MET, MOR, and KET, respectively. Recovery rates ranged from 73% to 134% across urine, hair, saliva, and sewage samples, with intra-assay precision consistently below 15%, indicating robust performance in complex matrices. Furthermore, we developed a multiplexed AIEFM-FQICS, enabling the simultaneous detection of three illicit drugs, thereby enhancing detection efficiency and reducing the cost. Generally, this work presents a highly sensitive, field-deployable platform for real-time monitoring in drug interdiction and public safety emergencies, offering substantial potential for practical anti-drug applications.