Design And Application Of Rhodamine Fluorescent Probe For Heavy Metal Ion

Metals ions play an important role in maintain the balance of environment and life system.However,the concentration is too high or too low will cause system disorders.Fluorescent probes have been widely used in the detection of metal ions due to the advantages of high sensitivity and selectivity.Therefore,this paper has designed and synthesized three new fluorescent probe rhodamine derivatives.The structures and properties have been carefully analyzed using ¹H NMR,ESI-MS,theoretical calculation and spectral analysis methods.Among them:?1?A rhodamine-2-thioxoquinazolin-4-one derivative?R1?has been synthesized by an addition-elimination reaction of rhodamine 6G ethylenediamine with methyl2-isothiocyanatobenzoate,which exhibits high selectivity and sensitivity as a fluorescent sensor toward Fe³⁺.Moreover,R1 could sense Fe³⁺by“naked eye”with a color change from colorless to yellow.To detect the practicability of the sensor,the test of Fe³⁺in real water samples and glioma cell line U251 has also been demonstrated.In addition,single crystal structures of R1·1.5H₂O·0.5CH₃CN,as well as the possible intermediate of R1 with Ag⁺and Hg²⁺ions were reported.?2?A rhodamine derivative?R2?has been synthesized by an additive reaction of rhodamine 6G hydrazide with methyl 2-isothiocyanatobenzoate,which shows high selectivity and sensitivity as a fluorescent sensor toward Cu²⁺.The detection limit of Cu²⁺ion is 4.72×10^-2?M.R2 could also test Cu²⁺by“naked eye”with a color change from colorless to pink.This selective signaling behavior is not affected by other cations that might be present in the environmental samples.The application of the fluorescent sensor in monitoring intracellular Cu²⁺in HeLa cells was also demonstrated.?3?A new rhodamine-based derivative bearing pyrrole unit,R3 was synthesized as a dual-mode Cu²⁺selective sensor via the rhodamine ring-opening approach and ratiometric displacement:A colorimetric and“off-on”signal for Cu²⁺through rhodamine ring opening in R3 and ratiometric fluorescent signal output when Cu²⁺displaces the bound Cd²⁺in the R3-Cd²⁺complex can be observed.The experimental result exhibits that R3 could also be applied to the imaging of living cells.The dual mode and effective molecular fluorescent has high research and application value to detect the same metal ions.