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Oxytetracycline (OTC) is an environmental pollutant caused by the abuse of antibiotics, and its content in water is closely related to human health. Therefore, the development of a simple, rapid, and accurate method to detect OTC has become desirable. In this work, a ratiometric fluorescence probe based on deep red emissive CdTe quantum dots (QDs) modified by mercaptopropionic acid and Eu3+ is developed to accurately and rapidly detect OTC in water. After the addition of OTC, the photoluminescence intensity of CdTe QDs at 698 nm remains almost unchanged, while the peak at 617 nm intensifies within 40 s due to the coordination of Eu3+ with OTC. An excellent linear relationship is present between the photoluminescence intensity ratio of I617/I698 and the concentration of OTC. The limit of detection of the probe towards OCT is 5.4 nM. In addition, the probe shows good selectivity and anti-interference ability for OTC in the presence of other antibiotics, including other antibiotics, ions, and amino acids. The probe has been successfully applied to detect OTC in actual samples, demonstrating its potential for environmental application. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR)-II fluorescence and photoacoustic (PA) dual-model imaging-guided photothermal therapy (PTT) can precisely diagnose and treat tumors and evaluate the therapeutic efficacy in real-time. Herein, we utilized a donor-π-acceptor (D-π-A) structured hemicyanine dye (named M1) with a large conjugated structure and strong intramolecular charge transfer effect and demonstrated that the aggregation of M1 could significantly enhance its photophysical performance by improving its photostability and photothermal conversion capability as compared with M1 in a single molecular state. Furthermore, we prepared water-dispersible NIR-II fluorescent nanoparticles (M1 NPs) by wrapping M1 with DSPE-PEG2000-NH 2 . The obtained M1 NPs exhibit strong NIR-I absorption and NIR-II fluorescence with their maxima at 734 and 1040 nm, respectively, with a fluorescence quantum yield of 2.84%. Moreover, M1 NPs also exhibit excellent biocompatibility, good photostability, and high photothermal conversion efficiency of 77.5%. In vitro and in vivo experiments reveal that M1 NPs can effectively image tumors through NIR-II fluorescence and PA signals, inhibit DNA replication, trigger cytoskeleton collapse, and eventually induce tumor cell apoptosis under 808 nm laser irradiation. Based on these outstanding properties, the application of M1 NPs in PA and NIR-II fluorescence imaging-guided PTT of tumors is demonstrated., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Co-published by Nanjing University and American Chemical Society.)