Fluorescent Probe Synthesis And Composite Nanofibers For The Detection And Study Of Cu²⁺ In Water

Heavy metal ions are widespread in nature,and environmental pollution is becoming more and more serious due to the discharge of industrial wastewater.Excessive content of heavy metal ions in water will not only damage the ecological environment,but also endanger human health.Therefore,it is particularly important to develop an effective detection method for heavy metal ions in water.In the past,people have established a variety of heavy metal ion detection methods such as atomic absorption and voltammetry,but these methods require expensive equipment and operating costs,as well as professional analysts.Relatively speaking,fluorescent sensors have the advantages of low cost,high sensitivity,and short response time,and are research hotspots in recent years.With the deepening of research,people have paid great attention to the fiber thin film sensor loaded with fluorescent probes.Compared with small-molecule probes,thin-film materials are easy to use and easier to implement.Electrospinning is a nanofiber preparation technology that has emerged in recent years.The nanofiber membrane prepared by this method has the advantages of small diameter and large specific surface area,and is an ideal material for preparing thin film sensors.This paper designed and synthesized a series of organic small molecule fluorescent probes based on halogenated fluorescein,and investigated their aggregation-induced luminescence properties and metal ion detection capabilities.Combined with the electrospinning technology,nanofiber test paper with the ability to detect metal ions was prepared.The main contents are as follows:1.Preparation of hydrazide compounds starting from 5 kinds of halogenated fluorescein and hydrazine hydrate,subsequent Schiff base reaction with salicylaldehyde resulted in five fluorescent probes YF-I₄、YF-Br₄、YF-Br₄Cl₄、YF-Br2 and YF-Cl2.It was characterized by nuclear magnetic characterization and AIE luminescence.After determining the acetonitrile as the solvent through the organic solvent screening experiment,the luminescence performance of the probe in the acetonitrile/water mixed solvent.It was found that when the water content was greater than 80%,the probe showed obvious AIE luminescence performance.The quantum yield of the probes were determined based on the ultraviolet absorption spectrum and fluorescence emission spectrum data.It was found that the probe YF-Br₄ had better luminescence performance and the highest quantum yield,reaching 0.17,which had good application prospects in the field of environmental detection and biological imaging.2.Based on the research of the above five probes,the detection performance of the probes YF-I₄,YF-Br₄ and YF-Br₄Cl₄ for metal ions were mainly investigated,and it was found that all three probes could achieve sensitive detection of copper ions.After the addition of copper ions,the probe solution would quench the fluorescence,the fluorescence intensities were reduced by 9 times（538 nm）,7 times（541 nm）and 5times（603 nm）.The detection limits of fluorescence were 4.345×10^-9 mol/L,1.239×10^-77 mol/L and 5.869×10^-8 mol/L,respectively.Through interference experiments,it was found that the probe had good anti-interference ability,and could recognize and detect copper ions in the presence of other interference ions.In addition,the probes had good naked eye colorimetric recognition ability for copper ions.After encountering copper ions,it changed from yellow-green to colorless under the irradiation of ultraviolet lamps.3.Nanofiber test paper containing probe YF-I4 was prepared by electrospinning technology.The fluorescence spectrum and copper ion detection performance were studied.It was found that with the increase of the probe introduction amount,the fluorescence intensity of the test paper gradually increased.After the test paper encountered copper ions,fluorescence quenching occurred.The test paper changed from yellow-green to colorless under the irradiation of ultraviolet light.It has good application prospects in the detection of copper ions in water.