Synthesis And Properties Of Fluorescent Probe Based On Quinoline And Naphthalimide Derivatives For Metal Ions

Although trace amounts of metal ions are necessary for the living organisms.They play vital roles in biological systems and the environment,but excessive amounts are certainly harmful to the organisms.Thus,detecting metal ions of environmental and biological systems is a significant research filed in the environmental governance and human health.Fluorescent probe with high sensitivity and great selectivity has become an important method for environmental detection and in vivo analysis of metal ions.Quinoline and naphthimide are widely used as fluorescent probes owing to their outstanding coordination/reaction capability and photophysical properties.According to the recognition mechanism,we successfully designed and prepared four fluorescent probes based on quinoline and naphthimide for metal ions in this paper.The details are as follows:First,we synthesized a novel dual-functional rhodamine B-quinoline conjugation fluorescent probe,RHQ,for the distinguishable detections of Cu2+and Hg3+.Significantly,the probe exhibited excellent and sensitive off-on fluorescence and ratiometric Ultraviolet-visible(UV-Vis)absorption responses to both Cu2+ and Hg2+ in CH3CN-H2O(4:1,v/v).The recognition of the mechanism indicating that Cu2+ activated the opening of the rhodamine spirocycle and inhibited Excited-State Intramolecular Proton Transfer(ESIPT);while Hg2+ facilitated both the opening of the rhodamine spirocycle and the formation of a new special cycle of the quinoline unit,inhibiting both ESIPT and Photoinduced Electron Transfer(PET).Moreover,the RHQ can quantitatively detect Cu2+and Hg2+.Furthermore,the probe with low cytotoxicity was successfully administered to monitor Cu2+and Hg2+in living cells.Secondly,we synthesized a fluorescent probe(NI-QA)for Cr3+,which using naphthalimide acted as chromophore and quinoline as the recognition group.And we explored the sensing properties by fluorescence spectra.The results showed that NI-QA for Cr3+ exhibited high selectivity and strong anti-interference capability.The coordination ratio of NI-QA to Cr3+ is 1:1,which is attributed to inhibit C=N isomerization process,so the fluorescence intensity of NI-QA is remarkly enhanced.Moreover,a good linear correlation of the fluorescence intensity and the concentration of Cr3+(0～40 μM)was obtained,indicating that NI-QA could quantitatively detect Cr3+.Moreover,the probe has been successfully applied to the detection of Cr3+ in tap water and lake water.Thirdly,we prepared a Zn2+-based fluorescent probe,NI-Tpy,which using naphthalimide acted as chromophore and terpyridine as the ion recognition group.Then,we have studied the recognition of metal ions through fluorescence spectroscopy.The results showed that NI-Tpy for Zn2+ exhibited high selectivity and reversibility in the change of pH within 3 to 11.Moreover,a good linear curve was achieved in the linearity range from 0 to 10 μM of Zn2+.In addition,the complex ratio of NI-Tpy to Zn2+ is 2:1 due to inhibiting PET process.Moreover,the membrane ESF-NI-Tpy was prepared by electrospinning technology with NI-Tpy and cellulose acetate(CA).And it could visually recognize Zn2+.Finally,the fluorescent probe NI-SP was prepared to recognize Al3+ and Cu2+,which using naphthimide and spiropyran acted as the two fluorophores.After adding to Al3+ and Cu2+,the fluorescence intensity of probe increasing because the spiropyran unit in NI-SP was ring-opened and the PET process was inhibited.The "off-on" fluorescent probe responds to Al3+ and Cu2+ in a wide range of pH(pH=2～9).In addition,NI-SP still showed high selectivity to Al3+and Cu2+in the presence of other competing ions.Moreover,it could be used as an electrospun film of pH sensor with low-cost and reusable portable.