Study Of Lu/CdTe Composite Fluorescent Probe And Its Applications In The Detection Of Antibiotics Residues

At present,the overuse of antibiotics in society is a serious threat to human health and ecological stability.Therefore,it has become extremely imperative to conduct relevant research and analysis on safety testing techniques to detect antibiotics.The novel fluorescence-based antibiotics detection methods operate easily,respond sensitively and low detection limits,whereas nano fluorescent probes have the potential for medical and biosensing applications due to the size effect,tunable optical properties,simple surface modification.Therefore,developing high-efficiency and sensitive fluorescent probes and fluorescent sensors has great theoretical significance and worth application.In this thesis,Cd Te quantum dots were synthesized by hydrothermal methods and modified with carboxyl to coordinate with lutetium ions and then prepared the Lu/Cd Te composite fluorescent probe to detect doxycycline.The microstructure and fluorescence properties of the composite probe were investigated by physical and chemical characterization.At the same time,the coordination mode of metal ions with Cd Te quantum dots and doxycycline was analyzed.To realize the fast,sensitive and specific detection of doxycycline in lake water,pork and milk by Lu/Cd Te probe,the conditions for detecting doxycycline at different temperatures,times and p H were explored,and also the performance of the probe in detecting doxycycline,then the detection mechanism was investigated by fluorescence experiments.Based on this probe,a portable hydrogel sensor and a smartphone sensing platform were designed respectively by combining the high stability of polyvinyl alcohol and the high integration of the smartphone to realize an easy,quick and sensitive quantitative way to detect doxycycline.The results show that the introduction of lutetium ions excites the symmetry deviation-induced transition effect to enhance the red fluorescence at 721 nm of the Lu/Cd Te probe.With the increase of doxycycline concentration,the electron transfers from the surface trap of Cd Te quantum dots to lutetium/doxycycline,which promotes the non-radiative electron-hole rearrangement annihilation on the surface of Cd Te quantum dots,resulting in a gradual decrease of the probe fluorescence.While lutetium ions ligate with doxycycline through the carbon-oxygen leading to the conformational change of the doxycycline molecule to emit green fluorescence at 500 nm,thus constructing a ratiometric fluorescence system to detect doxycycline.The sensitive and rapid detection of doxycycline at the range of 0-28 μΜ within 10 s under the optimized conditions.The limit of detection was 36.6 n M.The results are obtained by spiked detection of doxycycline residues in lake water,milk and pork with recoveries of93%-103%.Based on the probe,the hydrogel sensor has been developed that provides a liquid-phase detection environment.The ratio of green to red of the sensing photos shows a linear relationship with the doxycycline concentration at the range of 0-28 μΜ,with a limit of detection of 53.6 n M.Meanwhile,the probe shows satisfactory results in real sample detection,which solves the problem high limit of detection(low sensitivity)of the paper sensors.In addition,the combination of the Lu/Cd Te probe with the smartphone through 3D printing technology,a device has been developed for miniaturization of the device,easy operation,and in situ quantitative detection with a limit of detection of 43.6 n M.Lu/Cd Te probe and its applications provided an easy and reliable strategy for the detection of antibiotic medicine in food and showed potential applications in food safety.