Digital surface-enhanced Raman spectroscopy sensing for identification and quantification of illicit drugs

Seized illicit drugs encountered in drug control efforts often present challenges such as low analyte concentrations and complex matrix interference, leading to potential false-negative results in drug detection. This significantly compromises detection accuracy and hinders the effectiveness of drug control efforts. This study innovatively constructed a slippery sensing platform based on digital SERS (SD-SERS). By leveraging the slippery surface for efficient enrichment of target analytes, thereby enhancing detection sensitivity, and combining it with the reliable quantitative capabilities of digital SERS, this platform significantly reduces false negatives in drug detection. Using heroin, cocaine, and etomidate—representative substances subject to severe societal abuse—as model analytes, the SD-SERS platform achieved sensitive identification of all three drugs at concentrations as low as 1 ng mL−1. It also provided accurate quantification of morphine in urine (1 ng mL−1), cocaine in Crack (10 ng g−1), and etomidate in e-liquids (10 ng mL−1). Furthermore, the SD-SERS platform effectively identified characteristic signals from binary and ternary drug mixtures. It also demonstrated potential for single-molecule detection at low concentrations. By integrating the enrichment capability of the slippery surface with the quantitative reliability of digital SERS, this research provides a novel solution to mitigate false negatives in drug detection arising from complex interfering factors.