Research On Uranyl Ion Fluorescent Probe Based On Aggregation-induced Luminescence

As a radioactive element,uranium is an important fuel for nuclear energy and weapons.Because of its radioactivity and chemically toxicity,the detection of uranyl ions(UO22+)in water arounding the nuclear industry is highly important,to ensure the health and safety of the public.Fluorescence analysis is one of the main methods for UO22+ detection with the advantages of simple equipment,convenient operation,high selectivity and sensitivity,in which fluorescent sensor is the most pivotal part.However,up to date,most organic fluorescent sensors have the disadvantages of low water solubility and aggregation-caused quenching(ACQ),which will limit their application.Notably,aggregation-induced emission(AIE)molecules receive great attention in the fluorescence detection of metal ions in recent years,since they exhibit strong fluorescence emission instead of ACQ effect in the aggregation state.Nonetheless,reports of AIE-based fluorescent sensors for UO22+ detection are rare.Thus,two AIE-based UO22+ sensors were synthesized by introducing different substituent into the tetraphenylethene fluorophore in this paper.The photophysical properties,fluorescence detection performance and fluorescence detection mechanism for UO22+ of these sensors were studied.The main research results are as follows:(1)According to the coordination mechanism of UO22+ with sensor,an AIE-based fluorescent sensor,1-[N,N’-bis(salicylidene)-(1,1 ’-biphenyl)-3,4-diamine]-1,2,2-triphenylethene(TPE-BSA),was synthesized,and its structure was characterized by MS,NMR and IR spectra.The photophysical properties of TPE-BSA in H2O/THF solution were investigated,indicating that TPE-BSA exhibited strong fluorescence emission and typical AIE character.The fluorescence titrimetric studies revealed that TPE-BSA could detect UO22+by the fluorescence quenching,and there was a linear relation between fluorescence intensity and concentration of UO22+ in the range of 0～0.6 μM.The detection limit of TPE-BSA was 3.9×10-8 M,which was lower than the limit of the WHO about UO22+ in drinking water(30μig/L,ca 1.1 × 10-7 M).Meanwhile,TPE-BSA was insensitive to pH(3.0～9.0)and other metal ions,implying TPE-BSA had good anti-interference performance.According to the results of NMR,Job’s plot analysis and quantum chemical calculations,the fluorescence detection mechanism towards UO22+ was ascribed to the coordination compound formed between UO22+ and TPE-BSA as well as the heavy atom effect of uranium.Furthermore,the concentration of UO22+ in drinking water sample was successfully determined by using TPE-BSA,which indicated that the TPE-BSA might provid a new method for the rapid detection of trace UO22+ in the environment system.(2)According to the mechanism of UO22+ promoting chemical reaction,an AIE-based fluorescent sensor 1-[N-salicylidene-(1,1-biphenyl)-amine]-1,2,2-triphenylethene(TPE-SA)with aggregation-induced emission(AIE)character was synthesized,and its structure was characterized by MS,NMR and IR spectra.The fluorescence titrimetric studies suggested that the TPE-SA exhibited a significant blue-shift from 540 nm to 500 nm and enhancement of the fluorescence with the addition of UO22+.And the fluorescence intensity at 500 nm increased linearly with UO22+ concentration in the range of 0～0.35 μM,with the detection limit of 1.1×10-8 M.Moreover,with the addition of UO22+,there were obvious color changes from yellow to yellow green under the UV lamp,which indicated that TPE-SA could detect UO22+in a convenient way even by the naked eye.In addition,the fluorescence intensity of TPE-SA was invulnerable to the pH value(4.0～9.0)and other metal ions.According to the studies of NMR,MS and fluorescence lifetime,the hydrolysis of TPE-SA played a key role in the UO22+ sensing properties of TPE-SA,in which the product exhibited different fluorescence emission.All results indicated that TPE-SA provided a possibility for the rapid detection of trace UO22+ in the environment system.(3)The similarities and differences between TPE-BSA and TPE-SA were compared.TPE-BSA and TPE-SA exhibited similar AIE properties in H2O/THF solution,but the detection limit of TPE-SA(1.1×10-8 M)was lower than that of TPE-BSA(3.9×10-8M).The reason was that they had different detection mechanism with UO22+.TPE-BSA was based on the fluorescence quenching caused by coordination between UO22+ and TPE-BSA as well as heavy atom effect of U atom,while TPE-SA was based on the the hydrolysis of the TPE-SA promoted by UO22+.The studies of the reasons for the different mechanisms are still underway.The above researchs have basic scientific value and important application prospect.The comparative study on the detection mechanism of two AIE-based sensors can provide an important reference for the development of detection trace UO22+.Two kinds of AIE-based fluorescent sensors have great advantages in selectivity and sensitivity,which may be applied to the rapid detection of trace UO22+ in environmental system.