Construction And Performance Of Metal Ion Fluorescent Probes Based On Rhodamine Derivatives

Metal ions emitted from industrial and agricultural production can enter the natural environment through waste gas,waste water and waste residue,causing environmental pollution.More seriously,these metal ions can enter the human body through enrichment in the food chain,thereby endangering human life and health.Therefore,it is important to monitor metal ions efficiently.Fluorescent probe technology is widely used for ion detection because of its simplicity,high sensitivity,and endogenous detection.However,the currently reported fluorescent probes usually suffer from poor ligandins ability,complex synthesis,need for organic reagents for detection,long response time,and single morphology.In this paper,four novel rhodamine-based fluorescent probes were constructed for the detection of different metal ions using rhodamine B as a fluorophore.The structures of the probes were verified by ESI-MS,¹H NMR,and ¹³C NMR,and the performance of the probes was investigated by UV absorption spectrometry,fluorescence spectrometry,and the MTT method.The main studies are as follows:（1）A fluorescent probe RBJF was developed based on rhodamine B fluorophore with 1,3-phenylenediamine and pyridine-3-sulfonyl chloride as functional groups for the rapid detection of Al³⁺.The development of the probe RBJF effectively overcame the shortcomings of previous Al ion probes such as poor coordination ability,complex synthesis and harmful detection reagents,with a detection limit of 0.314μM and a binding constant of 0.455×10⁴ M^-1.The probe RBJF has shown good properties of low toxicity in biological experiments and can be used for the detection of Al³⁺in human breast cancer cells（MCF-7）,zebrafish and soybean root tissues and for fluorescence imaging.The detection data of the probe RBJF in natural water samples indicate that the probe has a highly practical application for the detection of Al³⁺in complex environments.（2）A fluorescent probe RBPH was developed for the rapid detection of Fe³⁺based on rhodamine B fluorophore with hydrazine hydrate and pyridine-3-sulfonyl chloride as functional groups.Compared with the fluorescent probes for Fe³⁺reported in previous work,the probe RBPH shortened the detection time of Fe³⁺from a maximum of 120 min to 5 min,with significant detection advantages.The detection limit was 75.9 n M and the binding constant was 0.608×10⁴M^-1.Biological experiments have shown that the probe has the advantages of good biocompatibility,low toxicity,and high cell penetration capacity.Meanwhile,the probe RBPH was also successfully applied to the detection of Fe³⁺ions in He La cells and zebrafish with good fluorescence imaging effect.（3）Based on the rhodamine B fluorophore,a fluorescent probe RBSH was developed for the rapid detection of Hg²⁺using 2-amino-5-mercapto-1,3,4-thiadiazole as the functional group,which is different from the conventional complexed rhodamine-based fluorescent probes in that it introduces a sulfhydryl group that can react with Hg²⁺to accelerate the efficiency of Hg²⁺detection.It has a detection limit of 5.9 n M,a binding constant of 1.658×10⁵ M^-1,and a response time of 60s.This provides an order of magnitude detection advantage over conventional rhodamine-based fluorescent probes.The probe RBSH also has the advantages of short response time,good biocompatibility,and high interference resistance,and can be used for the detection and fluorescence imaging of Hg²⁺in He La cells,zebrafish,and soybean root tissues.（4）A fluorescent probe RBCMC was developed for the rapid detection of Al³⁺based on rhodamine B fluorophore by EDC/NHS mediated carboxyl and amino reactions.The organic combination of small molecule probe and large molecule carrier makes the fluorescent sensor RBCMC have the advantages of both water solubility of carboxymethyl cellulose carrier and specific detection of Al³⁺ions.The detection limit of Al³⁺in water is 0.239μM and the binding constant is 1.92×10⁴ M^-1,which effectively solves the drawback of using organic solvent in the detection process of traditional fluorescent probes.The cellulose hydrogel developed based on the reversible probe RBCMC also shows corresponding advantages:First,the solid form of the hydrogel facilitates the carrying and use of the probe;Second,the Al³⁺can be detected by color or fluorescence changes;Third,its reversible property facilitates the reuse of the hydrogel sensor.