Naphthalimide Derivatives as Film-Based Fluorescent Sensors for Rapid Detection of Illicit Drugs

Film-based fluorescence sensors are attractive for illicit drugs detection due to their potential for rapid response, low limits of detection, and portability. However, it is still a significant challenge to achieve real-time identification of suspected illicit drugs using fluorescence detection. Herein, four novel 1,8-naphthalimide (NI) derivatives with different substituents at the 4-position, namely NI-1 [phenyl], NI-2 [4-({2-ethylhexyl}oxy)phenyl], NI-3 [4,4''-bis({2-ethylhexyl}oxy)-(1,1':3',1''-terphenyl)-5'-yl] and NI-4 [4-(dimesitylboraneyl)phenyl] are reported. The four NI derivatives had different thin film optoelectronic properties and mass densities, and showed distinct fluorescence responses to methamphetamine hydrochloride, 3,4-methylenedioxyamphetamine hydrochloride, cocaine hydrochloride, fentanyl hydrochloride, and tetrahydrocannabinol. The contrasting fluorescence responses of NI-1, NI-2, NI-3 and NI-4 were utilized as the basis for a constructed sensor array, which can distinguish between five drugs, three compounds commonly found around the home (paracetamol, aspirin and caffeine) and a null class (a blank swab) in 18 s with a mean classification accuracy of 81%. By grouping analyte predictions into binary “drug” and “other” categories, a 94% mean classification accuracy is achieved. This highlights the potential for thin film fluorescent NI derivatives to be used for rapid on-site drug screening.