Preparation And Properties Of Fluorescent Detection Films For Fe(Ⅲ) And Cr(Ⅵ) Ions In Drinking Water

Food safety has always been an important issue of global concern.The problem of water quality safety affects all aspects of our life.The fresh water resources on the earth are very scarce.The safety of drinking water is closely related to the basic survival of mankind to a great extent.Toxic pollutants in water,especially some heavy metal ions,have complex structures in water and are difficult to degrade,which is very harmful to people’s health.Therefore,people are very concerned about the content of heavy metals in water.Although traditional detection methods have low detection limit,they need large instruments or professional detection personnel,which limits their application in practice.Fluorescence detection has attracted extensive attention and attracted great interest of researchers because of its rapid response and simple operation.Therefore,considering human health problems,there is an urgent need to develop a simple and effective detection method,which can detect heavy metal ions in drinking water quickly and in situ.To this end,this paper has done the following research:（1）Fluorescence detection of heavy metal ions in Eu-DBN rare earth complexesThe anionic lanthanide complex（HNEt₃）⁺[Eu（DBN）₄]^-（Eu-DBN for short）was successfully synthesized from EuCl₃·6H₂O（europium chloride hexahydrate）and ligand DBN（1,3-diphenyl-1.3-propanedione）.A series of characterization experiments were carried out by infrared spectroscopy,UV-vis spectroscopy and X-ray powder diffraction analysis,which proved the successful synthesis of the material.The material has excellent fluorescence performance,high luminous intensity,strong red light emission under UV lamp and good water stability.Its fluorescence intensity can be maintained in water for at least 72 hours,and maintains good fluorescence intensity in acid-base water environment with p H value in the range of 5-12.Importantly,Eu-DBN can be used as a chemical sensor to show high selectivity and sensitivity to iron ion(Fe³⁺),chromate ion(CrO₄^2-)and dichromate ion(Cr₂O₇^2-)in the form of fluorescence quenching,and the detection limit is as low as micromolar level(Fe³⁺cation is 1.3×10^-12 M,CrO₄^2-anion 9.7×10^-8 M,Cr₂O₇^2-anion is 1.1×10^-8 M),at the same time,the material has good recyclability,the fluorescence intensity can be restored in a short time after removing ions,and can be used repeatedly for at least 5 times.Finally,the detection mechanism of Eu-DBN for iron ion(Fe³⁺),chromite ion(CrO₄^2-)and dichromate ion(Cr₂O₇^2-)is verified by theoretical calculation.It can be seen that Eu-DBN is a potential material for detecting heavy metal ions in water and has high practical value.（2）Fluorescence detection of heavy metal ions in detection film Eu-DBN-SMEu-DBN was doped into polymethylmethacrylate（PMMA）,and the fluorescent film Eu-DBN-SM was successfully prepared.The film inherits the fluorescence properties of Eu-DBN,has high luminous intensity and shows strong red light under UV lamp.Similarly,it also showed good selectivity and sensitivity to iron ion(Fe³⁺),chromate ion(CrO₄^2-)and dichromate ion(Cr₂O₇^2-)in the form of fluorescence quenching.The detection limits are iron ion(Fe³⁺):9.7×10^-8 M.chromate ion(CrO₄^2-):1×10^-3 M.dichromate ion(Cr₂O₇^2-):3.4×10^-7 M.The circulation is good and can be tested at least five times.At the same time,as the detection film,the film was immersed in an aqueous solution containing iron ion(Fe³⁺),chromate ion(CrO₄^2-)and dichromate ion(Cr₂O₇^2-)respectively,showing visible fluorescence quenching to the naked eye,and the fluorescence recovered instantaneously after removal.Therefore,the film can realize the rapid and in-situ detection of iron ions(Fe³⁺),chromate ions(CrO₄^2-)and dichromate ions(Cr₂O₇^2-)in drinking water anytime and anywhere without the need of detection instruments,simplify the detection process to a great extent,and has a high practical prospect.