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^-1 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.