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.