Utilizing Different Diffusion Mechanisms for Thin Film Fluorescence-Based Detection and Discrimination of Illicit Drug Vapors.

Film-based fluorescence sensors have been demonstrated to be powerful tools for real-time detection of trace chemical vapors. While explosive vapor detection via fluorescence quenching has been widely explored, fluorescence-based real-time detection and identification of illicit drug vapors remains a challenge. Here, we report two perylene diimide-based sensing materials, P1 and P2 , incorporating 2,2-dihexyloctanyl chains and 4-[tris(4-{ tert -butyl}phenyl)methyl]phenyl moieties at the imide positions, respectively. Quartz crystal microbalance with in situ photoluminescence measurements showed that N -methylphenethylamine, a simulant of methamphetamine (MA), diffused into films of P1 and P2 via Fickian and case-II mechanisms, respectively. The difference in the analyte diffusion mechanism led to P2 showing significantly faster luminescence quenching but slower luminescence recovery compared to P1 . Finally, the different diffusion mechanisms were used as the basis for developing a simple sensor array based on P1 and P2 that could selectively detect free-base illicit drugs (MA, cocaine, and tetrahydrocannabinol) from potential interferants (organic amines, alcohol, and cosmetics) within 40 s.