Novel Rhodamine B-based Fluorescent Probes: Design,Synthesis And Application On The Fe³⁺ Detection

The fluorescent probe is an important detection method used for metal ions detection due to its advantages such as high sensitivity,rapidity and convenience,etc.Nowadays,varieties of fluorescent probes have been developed for the detection of Fe³⁺,which greatly advanced the research progress for Fe³⁺.And also these probes play a guiding role for environmental protection,medical care and so on.However,the reported fluorescent probes for Fe³⁺still have some defects that need to be overcome,such as slow response,low sensitivity,and poor water solubility.Therefore,it is in great demand to develop fluorescent probes for Fe³⁺detection with advantages of fast reponse,high sensitivity,and good water solubility.In our study,rhodamine B and dansylamine compounds are used as fluorophores with other recognition groups to explore the effect of complexes on the spectral properties and applications,aiming to develp fluorescent probes with high sensitivity and water solublility for rapid detection of Fe³⁺in environmental and biological samples.The main research contents are as follows:Five turn-on fluorescent probes?RE1,RE2,RE3,RE4 and REA1?based on rhodamine B and ethylenediamine groups were designed and synthesized to detect Fe³⁺in water solution.The Fe³⁺ions could be detected by these probes in pure water,which exhibted low limits of detection?LOD?between 18.6 and 29.4 nM.The selectivity and interference experiments showed that the probes had strong response to Fe³⁺and could not be interfered by the other ions.In addition,the binding mode of probes with Fe³⁺was proved to be 1:1 stoichiometry in the probes-Fe³⁺complex by Job's plot,EIS-MS.And the binding ability of probes with Fe³⁺were shown as the order of RE2>REA1>RE4>RE3>RE1.The sensing mechanism of RE2with Fe³⁺was investigated by ¹H NMR titration and DFT calculation.Furthermore,RE2 was further utilized to detect Fe³⁺in living cells and practical water samples.Two turn-on fluorescent probes?RBA2 and RBA3?based on rhodamine B and hydrazide groups were designed and synthesized to detect Fe³⁺.It was found that RBA2 and RBA3could be used in detecting Fe³⁺rapidly in methanol water?1:1,v/v?solution and exhibted low LODs detection which could be achieved 12.8 and 11.0 nM.The selectivity and interference experiments showed that RBA2 and RBA3 had strong response to Fe³⁺and can not be interfered by the other ions.In addition,the binding mode of probes to Fe³⁺was proved to be1:1 stoichiometry in the probes-Fe³⁺complex by Job's plot and were well conformed by ESI-MS,¹H NMR titration experiments and DFT calculation results.Furthermore,the Fe³⁺-binding capabilities of RBA3 excess to that of RBA2 were also determined by the binding association constants and computational calculations.Finally,probes?RBA2 and RBA3?were further utilized to detect Fe³⁺in living cells and practical water samples,indicating its promising prospect in both biology and environment field.A quenching fluorescent probe?NB?based on dansyl group was designed and synthesized to detect Fe³⁺.It was found that NB could be used in detecting Fe³⁺rapidly in methanol water?1:1,v/v?solution and exhibted LOD 4.7?M.The selectivity and interference experiments showed that NB had high selectivity for Fe³⁺and could not be interfered by the other ions.In addition,the binding mode of NB to Fe³⁺was proved to be 2:1 stoichiometry in the NB-Fe³⁺complex by Job's plot.Furthermore,NB could be used to detect Fe³⁺in the practical water samples.