Synthesis And Properties Of Fluorescence Probes Based On Rhodamine B

In recent years,fluorescence sensing methods have attracted widespread attention due to their simple operation and well reproducibility,and were often used to identify metal ions.Rhodamine B and its derivatives were colorless and have no fluorescence signal in the closed loop state of spiro lactam due to their excellent structural characteristics and spectral properties.These show obvious color changes and strong fluorescence signals when combined with recognition ions.The imine bond（-C=N-）is generally a structure formed by the condensation of amino and aldehyde groups,which has a good chelating effect with metal ions and can effectively capture metal ions,forming stable complexes.With rhodamine B as the skeleton,five probes JT1,JT2,JT3,JT4 and JT5 were synthesized by Schiff base reaction.Cu²⁺,HSO₄^-and Sn⁴⁺were identified by fluorescence and colorimetry.Firstly,JT1,JT2 and JT3 were synthesized with rhodamine B as the skeleton.Fluorescent probes JT1 emit yellow fluorescence signals in the DMSO/H₂O（4:1,v/v）system.When the excitation wavelength is 356 nm and Cu²⁺is added,a significant decrease in the fluorescence intensity of JT1 can be observed at 517 nm.Under a 365 nm ultraviolet lamp,the yellow fluorescence signal disappears,and the solution changes from colorless to red under visible light.By mass spectrometry and Job’s plot,it can be inferred that the binding ratio is 1:1.Fluorescent probe JT2 can also recognize Cu²⁺by fluorescence and colorimetry in DMSO/H₂O（4:1,v/v）system,the fluorescence emission spectrum shows that probe JT2has a strong emission peak at 521 nm in 345 nm excitation wavelength.After adding Cu²⁺,the fluorescence emission peak of JT2 blue shifted and decreased at 521 nm,meanwhile,a new fluorescence emission peak appeared at 588 nm.The disappearance of yellow fluorescence was observed under a 365 UV lamp,and the solution was observed to change from colorless to red under visible light.It can be inferred that the binding ratio is 1:1 by mass spectrometry and Job’s plot.Fluorescent probe JT3 specifically recognizes HSO₄^-and colorimetrically recognizes Cu²⁺in DMSO/H₂O（4:1,v/v）system.When the excitation wavelength was 460nm,the fluorescence intensity of JT3 decreases significantly at 524 nm after the addition of HSO₄^-,and the yellow fluorescence signal disappears under 365 UV light.When Cu²⁺was added to JT3 solution,new absorption peaks appeared at 409,520 and 557 nm,and the solution turned red under visible light.Through mass spectrometry and Job’s plot,it can be inferred that the binding ratio is 1:1.Furthermore,the binding mechanism between HSO₄^-and JT3 was further studied through nuclear magnetic titration.Probes JT1,JT2,and JT3 further demonstrate their sensing mechanism through theoretical calculations.In addition,test strips and zebrafish imaging experiments were successful conducted on JT1,JT2,and JT3,providing a foundation for further testing of Cu²⁺and HSO₄^-in the environment and biological systems.Secondly,fluorescence probe JT4 detects Cu²⁺by switching the fluorescence signal"on-off"in DMSO/Et OH（4:1,v/v）,and colorimetrically recognizes Cu²⁺.After the addition of Cu²⁺,the emission peak intensity of JT4 at 525 nm decreased and the yellow fluorescence signal disappeared under the 365 nm UV lamp.And three new absorption peaks were observed in the UV spectra at 404,519 and 559 nm,respectively.At the same time,accompanied by the solution rapidly turning red.Additionally.The mass spectrometry and Job’s plot were provided to demonstrate a binding ratio of 1:1.Finally,the practicality of light probe JT4 was successfully studied using test strips and zebrafish,which showed that JT4can successfully detect Cu²⁺in test strips and zebrafish,providing a basis for further testing of Cu²⁺in the environment and biological systems.Finally,the fluorescence probe JT5 showed no fluorescence signal and exhibited week emission peak in DMSO/H₂O（4:1,v/v）solution.When Sn⁴⁺was added,the emission peak of JT5 shifted red from 587 nm to 591 nm,and the fluorescence intensity increased 63 times.Strong red fluorescence was observed under 365 nm UV light.At the same time,the color of the solution turns red.The sensing mechanism of probe JT5 for Sn⁴⁺can be inferred from Job’s diagram,nuclear magnetic titration,mass spectrometry and fluorescence titration experiments that the amide ring of rhodamine B is open,and theoretical calculation is further helpful to prove its sensing mechanism.In addition,successful test strips and zebrafish imaging experiments were conducted to demonstrate the practicality of probe JT5,laying the foundation for further testing Sn⁴⁺in the environment and biological systems.