Facile fabrication of luminescent Tb@HOF-based films as a highly sensitive platform for detecting nicotine and its metabolite cotinine via fluorescence sensing and a smartphone

Nicotine, as a major component of cigarette smoke and second-hand smoke (SHS), is highly harmful to human health because of its carcinogenic potential. Hence, detecting it in indoor air is very important. Cotinine is the first metabolite of nicotine, and its detection can directly reflect human exposure to SHS. Therefore, developing a portable, highly sensitive, and visual sensing platform to simultaneously detect nicotine gas and cotinine is desired for ensuring environmental safety and human health. Herein, Tb@MA-TMA/Zinc Film (1) and Tb@MA-TMA/AG Film (2) were fabricated via electrophoretic deposition (EPD) and agarose hydrogel (AG), respectively, and could detect nicotine gas and cotinine based on a dual-mode of fluorescence and smartphone. Both 1 and 2 emitted a bright green fluorescence of Tb3+ ions due to ligand-to-metal charge transfer (LMCT) from MA-TMA to Tb3+ ions. 1 Could specifically detect nicotine gas with high sensitivity, excellent anti-interference ability and good repeatability with a detection limit (DL) of 0.042 mu M. For the detection of cotinine, 2, the first reported fluorescence sensor exhibited outstanding selectivity, good sensitivity, and low DL both in aqueous solution and real saliva with DLs of 0.95 and 1.07 mu M, respectively. The sensing mechanisms of 1 and 2 toward nicotine gas and cotinine were investigated. Furthermore, the intelligent sensing platform was constructed by combining a smartphone with sensors 1 and 2, which could realize the visual quantitative detection of nicotine gas and cotinine with low DLs of 0.061 and 1.20 mu M. This work not only provides two facile approaches to fabricate portable Tb@MA-TMA-based films but also proposes a new way to combine a smartphone with fluorescence sensor to realize visual detection in practical applications.