A Carbon-Dot Sensing Probe for Screening of Date Rape Drugs: Nitro-containing Benzodiazepines

Abstract

Simple, low-cost, rapid, selective, and sensitive sensing kits are required for screening of illicit date rape drugs such as nimetazepam, flunitrazepam, clonazepam, and nitrazepam in beverages. Because of low solubility of these analytes in aqueous solution, hydrophobic carbon dots (hC-dots) are needed. In this study, hC-dots are prepared from D-phenylalanine through a hydrothermal route, which have been used for screening of the analytes. To minimize matrix interference in various beverages, including beer, red wine, whisky, and orange juice, liquid-liquid extraction of the analytes using toluene for 5 min is required before quantitation based on analyte induced fluorescence quenching of the hC-dots at 430 nm when excited at 365 nm. This assay allows the quantitation of nimetazepam down to 7.24 μM, which is lower than that found in the beverages associated with drug-facilitated sexual assault (DFSA). The assay is selective toward nitro-substituted benzodiazepines over popular abused drugs, including 4-chloroethcathinone, cocaine, heroin, 4-hydroxybutyric acid, ketamine, and methamphetamine. Since only hC-dots (dispersed in 0.5 mL toluene), a handheld UV light (365 nm), and a camera (or smartphone) are required, this simple, low-cost, rapid, and selective sensing system is ideal for beverage analyses at DFSA crime scenes.