Study On A Metal Ion Fluorescent Probe Based On Spiropyran

The structure of spiropyran can change reversibly under different external conditions,that is,the colorless closed loop of spiropyran can be reversibly transformed into a colored open loop.Due to its special structure,spiropyrans are used as molecular devices and sensors,respectively,and are particularly widely used in the fields of photoelectric materials and chemical analysis.In this paper,the novel spiropyrans,which can increase the binding ability of spiropyran ring-opening bulk cyanine with metal ions and can combine with specific metal ions,were synthesized through introduced the introduction of methoxy,tert-butyl,coumarin and other groups.And the detection of metal ions was studied deeply.In addition,polysiloxane containing spiropyran was synthesized by grafting reaction.The paper mainly includes the following two parts:The first part is the synthesis and structural characterization of spiropyran small molecule SP₁,SP₂,SP₃,SP₄,SP₅ and spiropyran polymer SP₆.SP₁ and SP₂ were obtained by reaction of 1,2,3,3-tetramethylindolin with different salicylaldehyde.The yields of the two spiropyran molecules were 67%and 53%,respectively.Spiropyranes SP₃,SP₄,SP₅ were obtained from 1-allyl-2,3,3-trimethylindolin.The yields were 47.5%,39.6%and 27.8%,respectively.Spiropyran SP₆was obtained by the addition of spiropyran SP₄ monomer to polymethylsiloxane through the hydrosilylation reaction.The yield was 39%.Spiropyran small molecules were characterized by¹H NMR,¹³C NMR and MS.Spiropyran polymer SP₆ was characterized by GPC method.The second part mainly studies the performance of SP₁,SP₂ target spiropyran molecules and the recognition performance of metal ions.The recognition performance of the target probes SP₁and SP₂ was investigated by visual colorimetry,ultraviolet absorption spectroscopy and fluorescence spectroscopy.Spiropyran SP₁ probe:In the colorimetric method,the light yellow SP₁probe solution?the solvent is absolute ethanol?is sequentially added with the same concentration of different metal ions(Ag⁺,Na⁺,Fe²⁺,Ni²⁺,Cr³⁺,Cu²⁺).The color of the solution did not change significantly and remained light yellow;the color of the solution added with Co²⁺,Al³⁺,Li⁺became lighter and nearly colorless,and the color from dark to light was Co²⁺,Li⁺and Al³⁺;the solution added with Sr²⁺and Zn²⁺was changed.It is light gray and the Sr²⁺ solution is slightly darker than Zn²⁺.In the fluorescence spectrum,when the excitation wavelength is?_ex=321 nm,the probe's emission peak is at 450 nm.Li⁺,Sr²⁺and Al³⁺probe solutions are added at 450 nm to show a distinctly enhanced emission peak,and the intensity of Al³⁺and Sr²⁺.Similarly,it is about five times that of the remaining ions,and the intensity of the emission peak of Li⁺is the next,about four times that of the remaining ions.After UV absorption spectroscopy and fluorescence spectroscopy analysis,compared with other metal ions(Co²⁺,Ag⁺,Hg²⁺,Ni²⁺,Cu²⁺,Na⁺,Fe²⁺,Ce³⁺,Cr³⁺,Zn²⁺),SP₁ probe can be used to identify Sr²⁺,Al³⁺,Li⁺and the best recognition performance of Al³⁺,and has a shorter response time?within 10 s?and better sensitivity.In the anti-interference test of the probe,the interference ions included Zn²⁺,Fe²⁺,Ni²⁺,Cu²⁺,Co²⁺,Na⁺,Cr³⁺,Hg²⁺and Ag⁺.It was found that in addition to the addition of Sr²⁺,Al³⁺and Li⁺,strong emission peaks occurred.After other single ions were added,There was no significant change in fluorescence intensity.This result indicates that the probe has good anti-interference performance.By measuring the fluorescence spectra of mixed solutions of different concentrations of metal ions and spiropyran SP₁ probes,the lowest detection limit of probe detection ions was obtained.The detection limit of the probe for Al³⁺,Sr²⁺and Li⁺was 10?M,24?M,and 20?M,respectively.For spiropyran SP₂ probe:visual colorimetry showed that the spiropyran solution with Cu²⁺,Ce³⁺and other trivalent metal cations showed obvious color changes.The probe solution was colorless,and the ions added with Cu²⁺and trivalent state were orange yellow solutions.Therefore,the metal ions with Cu²⁺and trivalent state could be detected.By fluorescence spectrometry,when the excitation wavelength is 400 nm,the emission peak of spiropyranes solution added with Ce³⁺is about 2 times higher than that of other spiropyranes solution added with or without metal ions.SP₂probe can be used to identify Cu²⁺,Ce³⁺and trivalent metal cations by ultraviolet absorption spectra and fluorescence emission spectra.In SP₂ probe to detect the anti-interference experiment of Ce³⁺(add interference ions including Li⁺,Na⁺,Ag⁺,Sr²⁺,Ni²⁺,Co²⁺,Hg²⁺,Cu²⁺,Zn²⁺,Cr³⁺,Al³⁺,Nd³⁺,Yb³⁺,La³⁺,Fe³⁺and Bi³⁺),found that in addition to join Cu²⁺prompted fluorescence intensity decrease,after adding other metal ions did not make the fluorescence intensity is reduced,showing that the probe SP₂ detection Ce³⁺has good anti-interference.The fluorescence intensity of SP₂ probe solution with different concentrations of Ce³⁺was determined for three times.The maximum fluorescence intensity was taken and the corresponding fitting curve was made.The minimum detection limit of Ce³⁺detected by SP₂ probe was calculated to be 1.72×10^-6 M.Through Job's curve method,it was found that the complex showed the maximum absorption intensity at 0.5.It can be inferred that SP₂ and Ce³⁺were complexed in a 1:1 manner,and the possible complexing modes of SP₂ and Ce³⁺were given.Probe SP₂ was used to determine Ce³⁺in actual water sample.It was found that the solution color changed rapidly from light purple to yellow when an equivalent of Ce³⁺was added to the actual water sample.The results showed that the probe SP₂ was suitable for the visual detection of Ce³⁺ions in environmental water samples.