Design Of Fluorescent Probe Based On Quantum Dots And Its Visual Detection Of Uranyl Ions

Among the various ionic forms of uranium in aqueous media,the most stable and soluble form is uranyl,it can enter into ground or surface water systems through migration.Uranyl's chemical reactivity and radioactivity can be harmful to organisms like kidney,brain,and can further lead digestion,immunity,hematopoietic and reproductive system disorders.Therefore,it is necessary to develop high selective and selective methods to detect aqueous uranyl ions in environment.Combining the quantum dots of superior optical properties with fast-developing smart phones,this paper established an intelligent platform for sensitive,convenient and highly selective on-site detection of uranyl ions in aqueous solution.Furthermore,the probe was successfully applied in detection of uranyl ions in real samples.The main research contents of this paper are as follows:The first chapter focuses on several typical mechanisms for designing quantum dots(QDs)fluorescent probes,including fluorescence resonance energy transfer,internal filter effect,photo,induced electron transfer,and QDs aggregation-caused quenching.Combined with some current working examples for analysis,provides a theoretical basis for the design of the latter probe.Then,several classic models of ratio fluorescence probes are simply classified,including organic fluorescent molecular ratio probes,nanoparticle fluorescent molecular ratio probes,and ratio probes of nanoparticles combined with organic fluorescent molecules.The general design principles of each model are described and illustrated with examples.Finally,the development of smartphone detection application platform in recent years and its application prospect in the field of analysis are summarized.In the second chapter,we report a fluorescent method for sensitive and selective detection of aqueous uranyl ions using water-soluble CdTe QDs functionalized with 3-mercaptopropionic acid,which the fluorescence of the quantum dots could be quantitatively quenched through electron transfer mechanism.The detection limit of the method was estimated to be 4 nM.Furthermore,the probe was successfully applied in detection of uranyl ions in real samples,demonstrating its potential practical applications for monitoring of uranyl ions in environment.The third chapter established a smart phone application platform for rapid and on-site analysis of uranyl ion in aqueous based on ratiometric fluorescent probe.The ratiometric fluorescent probe is achieved by integrating carbon dots and CdTe QDs through chemical hybridization.The presence of uranyl ions greatly quenches the red fluorescence of the CdTe QDs,whereas the green fluorescence keeps constant,leading to obvious color change.An App and a 3D-printed accessory have been developed on a smartphone to analyze and calculate the content of uranyl ions on the basis of captured fluorescence signals from a test strip with immobilized probe.This new designed mobile detection system displays good analytical performance for uranyl ions in wide concentration range from 1 ?M to 150 ?M,which shows great potential application in controlling the nuclear industrial pollution.In the fourth chapter,a method for the detection of trace explosives with picric acid was established by using the fluorescence variation of perovskite quantum dots.The detection limit of this method is as low as 0.8 nM,which can effectively distinguish other structurally similar compounds.The quenching mechanism was deeply studied and discussed by the changes of the ultraviolet spectrum fluorescence lifetime and etc.before and after the reaction,and was further verified by computational simulation.Fluorescent test paper prepared by inkjet printer shows a well application prospect of perovskite quantum dots in the rapid visual detection of picric acid.