Screening of synthetic cannabinoids in herbal mixtures using 1-dodecanethiol-gold nanoclusters

Screening of synthetic cannabinoids (SCs), a new type of psychoactive substances, in herbal mixtures at crime scenes is in high demand. Because of the diversity and low aqueous solubility of SCs and the complicated matrix of herbal mixtures, screening reagents for SCs are limited. In this study, hydrophobic 1-dodecanethiol-stabilized gold nanoclusters (DT-Au NCs) were prepared for sensing SCs, including UR-144, JWH-018, and AB-PINACA. The DT-Au NCs exhibit emission at 620 nm when excited at 302 nm and are sensitive and selective for the detection of the three analytes in organic solution (V_chloroform/V_o-xylene: 1/4), with limits of detection of 7.7, 6.2, and 14.5 μM, respectively. The sensing mechanism is based on analyte inducing photoluminescence (PL) quenching through an electron transfer process. To screen the SCs in complicated herbal mixtures such as tobacco and Damask rose & fruit tea, a low-cost sensing kit consisting of a syringe, a filter, a sample container, and a glass tube containing 0.5 mL of DT-Au NCs solution (10 mg mL⁻¹) has been developed. The sensing kit allows simple and rapid screening of small amounts (w/w: 0.3%) of UR-144, JWH-018, or AB-PINACA in tobacco or in Damask rose & fruit tea, which can not be detected by using an expensive Raman system. The SCs eluted out from the herbal mixtures induce PL quenching of DT-Au NCs, which can be observed by the naked eye. Our results show great potential of the compact and low-cost sensing kit for the on-site screening of SCs in herbal mixtures.