Application Of Fluorescent Quantum Dots Based Probes In Environmental Detection

Selective detection of Fe³⁺,I^-and hydrogen peroxide?H₂O₂?is important in environmental monitoring,drug diagnosis,food safety and biological sample analysis.Therefore,it is very necessary and meaningful to establish a simple,sensitive,highly selective and stable detection method for real-time monitoring of the concentration of the above substances.Compared with other analytical detection methods,quantum dots have been used to replace some organic fluorescent groups due to their superior optical properties,mature synthesis methods,and simple operation.Based on the research literature,three quantum dot-based fluorescent probes were designed and synthesized to detect Fe³⁺,I^-and H₂O₂.The whole research includes the following two parts:The first part introduced two fluorescent probes for detecting H₂O₂.The first fluorescent probe is a CdSe/ZnS core-shell quantum dot with an emission peak of 570nm as fluorophore and the hydrophilic p-nonylphenol as a hydrogen peroxide-sensitive functional ligand on the surface of a quantum dot to formed p-nonylphenol-modified CdSe/ZnS quantum dots?p-HTP-QDs?performing by simple ligand exchange which with weakly fluorescent.The electron transfer process from the quantum dot to the ligand occurs under a certain excitation light,and the quantum dot electron/hole pair cannot be composited result in weak fluorescence;When hydrogen peroxide is present,the hydroxyl group on the surface of the quantum dot is oxidized to a carbonyl group,the oxidation process inhibits the above electron transfer,the quantum dot electron/hole pair recombines,and the quantum dot fluorescence recovery.Under optimized conditions,the fluorescence response of the probe has a good linear relationship with the hydrogen peroxide concentration of 0.31⁴.90 mM,and the detection limit is 0.14 mM.In addition,p-HTP-QDs have high selectivity to hydrogen peroxide and successfully detect hydrogen peroxide in actual water samples.The second fluorescent probe is similar to the first one.The CdSe/ZnS core-shell quantum dots with emission peak of 610 nm was used as fluorophores,and the fluorescence of water-soluble CdSe/ZnS quantum dots modified with thioglycolic acid are quenched by picric acid?PA?,and the fluorescence can restore in the presence of hydrogen peroxide.The system can also be used for the detection of hydrogen peroxide in an aqueous environment.Under optimal conditions,the detection limit is0.18?M.In the second part,we synthesized a new type of blue-green fluorescent phosphorous oxide quantum dots?PO QDs?by solvothermal method,which can be directly applied to the detection of metallic Fe³⁺.Due to the fluorescence quenching of the electron transfer mechanism,the fluorescence response has a good linear relationship with the metal Fe³⁺concentration of 0.14-0.98 mM,and the detection limit is 20?M.In addition,Ag⁺-mediated PO QDs can be used for the detection of I^-in aqueous environments.Ag⁺-mediated PO QDs exhibit strong fluorescence.When iodine ions are present and AgI is formed.Fluorescence quenching is caused by internal filtration.The detection method is simple in operation,rapid in fluorescence response,high in reproducibility,and the detection limit is 9?M under optimized conditions,and the detection of Fe³⁺and I^-in the actual water environment were successfully achieved.