Sensitive Cu²⁺ Detection By Reversible On-Off Fluorescence Using Eu³⁺ Complexes In SiO₂,in Chitosan/Polyethylene Oxide Nanofibers

Heavy metal pollution is caused by many industrial processes,including mining,metal manufacturing,pesticide synthesis,organic chemicals,pharmaceuticals,rubber,and plastic production.Among the heavy metal ions pollutants,Cu²⁺widely exists in natural water and industrial wastewater.High concentration of Cu²⁺is highly toxic and poses a threat to people's health and ecological environment.The content of heavy metal elements in the body has an important impact on human health.Excessive or lack of heavy metal elements in the body will have an impact on human health,and serious cases can lead to the occurrence of diseases,so it is particularly important to choose an efficient,accurate,and simple method to detect heavy metal ions(Cu²⁺).Chitosan(CH)is widely distributed in nature,which is the second largest natural polymer material.Chitosan contains many amino groups and carboxyl groups,which have strong adsorption for heavy metal ions.At the same time,chitosan is also considered as an excellent green and environmental protection material,which is non-toxic,antibacterial,degradable,and will not pollute the natural environment.Chitosan is also considered to be an excellent fiber material.Fibrotic chitosan can increase the specific surface area and adsorption effect.In order to further increase the fibrogenesis and practicability of chitosan,polyethylene oxide(PEO)was introduced to participate in the fiber forming to form CH/PEO composite nanofibers.The fluorescence properties of rare earth elements are widely used in probe,detection,and biological imaging,and have high sensitivity and visibility to heavy metal ions.However,the stability of rare earth complexes is poor.In order to solve this problem,inorganic component(SiO₂)can be introduced into rare earth complexes to increase their ability to cope with complex and diverse detection environment.However,the observation and detection efficiency of rare earth elements in the detection of heavy metal ions is poor.This problem can be solved by loading the complex with a carrier.In this paper,the electrospinning technology was used to prepare CH/PEO electrospinning film as the carrier of rare earth ions,and the CH/PEO-SiO₂@Eu(TTA)₃phen composite nano fluorescent fiber was successfully prepared,which can not only improve the practicability of Cu²⁺detection,but also increase the observation degree.The main achievements of this research are as follows:(1)The rare earth element chosen for this study is europium(Eu).Eu(TTA)₃phen complex was formed by complexing with 1,10-phenylline(phen)and 2-Thenoyltrifluoroacetone(TTA),and the complex was successfully embedded in silica(SiO₂)nanoparticles,nanomaterials are formed SiO₂@Eu(TTA)₃phen microspheres.TEM,HRTEM,Mapping,FT-IR and Fluorescence analysis were carried out,and SiO₂@Eu(TTA)₃phen nano-microspheres compared with Eu(TTA)₃phen,the fluorescence properties are improved obviously.(2)In this study,using acetic acid and water as solvents,using electrospinning technology,through the study of different parameters(solution parameters,process parameters)on the fiber morphology,CH/PEO nanofibers with good morphology were successfully prepared,the diameter of the fiber is 140±10 nm,the fiber distribution is relatively uniform,there is no adhesion or bead.The optimum parameters and spinning conditions for preparing CH/PEO nanofibers were obtained,that is,V(chitosan):V(PEO)=3:1,propulsion speed 2 m L/h,spinning voltage is 20 kv,receiving distance10 cm,temperature of 25?,humidity of 30%.CH/PEO-SiO₂@Eu(TTA)₃phen composite nano fluorescent fiber films were successfully prepared by blending the fibers and nanoparticles prepared under the above two optimal conditions.The film not only has the adsorption of chitosan fiber to heavy metal ions,but also has the fluorescence performance of Eu(TTA)₃phen complex and the sensitive detection performance of Cu²⁺.In this study,Cu²⁺solution was dropped into the prepared CH/PEO-SiO₂@Eu(TTA)₃phen composite nano fluorescent fiber film.Under the UV lamp,the film could be clearly seen from red to colorless,indicating that the film could be quenched quickly in the presence of Cu²⁺.In order to further study the influence of Cu²⁺solution at different concentrations and different times on the fluorescence properties of the films,the experiment was carried out on the above two variables of the film fluorescence analysis,it was found that the film has an obvious detection effect for 10?mol/L?100?mol/L Cu²⁺solution,and can be quenched very sensitive within 2 min.By adding EDTA,part of the film fluorescence can be recovered,and the effect of reuse can be achieved.