Synthesis And Detection Performance Of Photochemical Probes For Zn²⁺、 Pb²⁺、ONOO^- And Cu²⁺

In this paper,three near-infrared small molecule fluorescence probes were synthesized by using dicyanoisoflurone fluorophore（DCO）reacting with different modification groups for the specificity detection of Zn²⁺、Pb²⁺and ONOO^-,respectively.A colorimetric probe for the detection of Cu²⁺was synthesized based on the reaction of rhodamine B fluorophore with 3,5-dichlorosalicylaldehyde.1.A near-infrared fluorescence probe I was synthesized by Schiff base reaction between dicyanoisoflurone fluorophore group and thiophen-2-hydrazine carboxylate.The probe was combined with Zn²⁺and Pb²⁺at a stoichiometric ratio of 1:1,which blocked the PET process from C=N to dicyanoisoflurone,resulting in enhanced fluorescence of the solution after the reaction,with a maximum emission wavelength of 670 nm.The linear detection range of probeⅠfor Zn²⁺and Pb²⁺was 0-5.5μM,and the detection limit（LOD）and complex constant（K）for Zn²⁺were 1.59 n M and2.2×10⁵M^-1,respectively.The detection limit and complexation constant of Pb²⁺were 1.65 n M and 4.9×10⁵M^-1,respectively.Due to the reversible coordination between probeⅠand Zn²⁺and Pb²⁺,the probe can be reused under the action of EDTA and has been successfully used for quantitative analysis of Zn²⁺and Pb²⁺in water samples.At the same time,the detection paper based on the probe can realize the rapid detection of two kinds of ions.2.A near-infrared fluorescence probeⅡwas prepared by the reaction of dicyanoisoflurone fluorophore with 2-furanoylhydrazine.In the range of 0-1.8μM Zn²⁺concentration,the fluorescence intensity of the probe showed a good linear relationship with the concentration of Zn²⁺（R²=0.9911）,and the quantitative detection of Zn²⁺was realized with a fast response（30 s）.The detection limit of Zn²⁺was 2.7 n M and the complex constant was 2.0×10⁵M^-1.Because of the reversible coordination between probeⅡand Zn²⁺,the probe can be recycled under the action of EDTA.ProbeⅡcan detect Zn²⁺in environmental water samples visually.In addition,the probe can be prepared into Zn²⁺test paper.3.A near-infrared fluorescence probeⅢwas synthesized by condensation reaction of dicyanoisoflurone fluorophore with 1,4-dimethylpyridine iodide.The chemical reaction between ONOO^-and the probe changes theπconjugated system of the probe,making the color of the probe solution change from purple to pink and quenching the fluorescence.The maximum emission wavelength of probeⅢwas 720nm and the detection limit of ONOO^-was 25.77μM.The probe has the advantages of good selectivity,wide concentration detection range（0-126μM）,wide p H application range（2.0-11.0）,and can be used for the detection of ONOO^-in actual water samples.4.A colorimetric probeⅣwas synthesized by Schiff base reaction between rhodamine B fluorophore and 3,5-dichlorosalicylaldehyde.After the addition of Cu²⁺,spirolactam of probeⅣwas ring-opened by coordination reaction to form a complex with color changes.The complexation constant was 1.36×10⁵M^-1.The absorbance（560 nm）of the probe showed a good linear relationship with the concentration of Cu²⁺in the range of 0-3.5μM（R²=0.9939）.The probe has the advantages of good selectivity,high sensitivity（detection limit is 35.7 n M）,wide p H range（3.0-11.0）,and can be recycled under the action of EDTA.It can be used for the determination of Cu²⁺content in real water samples,and can be made into test paper to achieve rapid open-hole identification and detection of Cu²⁺.