Design,synthesis And Application Of Reaction-based Fluorescent Probes Based On The Xanthene

A variety of ions and active substances in the environment and organisms are very important for maintaining ecosystem balance and normal life activities of organisms,so the detection of these substances is of great significance.Based on convenient preparation,high sensitivity,good selectivity,response rapidly and high temporal and spatial resolution,fluorescent probes have gradually become important tools for the detection of various of ions and active substances.As a kind of important fluorescent probes,the reaction-based fluorescent probes used the specific chemical reactions between the analytes and the fluorescent probes to quantitatively detect the analytes.Therefore,this type of fluorescent probes has significant advantages over other types of fluorescent probes.Consequently,the reaction-based fluorescent probes have been widely used in real-time monitoring and fluorescence imaging and become an important branch in the field of fluorescence sensing.In this paper,we have designed and synthesized six reaction-based fluorescent probes base on the xanthene for detecting H2 S,Cys,pd0,Hg2+ and N2H4,respectively.The main research contents were as follows:(1)We have designed and synthesized two fluorescent probes LFA and RCHO towards H2 S based on different reaction mechanisms.The probe LFA possessed good water solubility and could detect H2 S in 99% aqueous solution.Through H2 S induced Michael addition-cyclization-elimination reaction,the probe could detect H2 S with rapid response(20 min),high selectivity and sensitivity(167 n M).The probe RCHO could quickly detect H2 S through aldehyde assisted thiolysis reaction mechanism.The response time of the probe was 12 min,and the detection limit of the probe was 97 n M.In addition,after reaction with H2 S,the color of the probe RCHO solutions changed significantly(from colorless to pink),therefore,H2 S could be monitored by naked eyes.Moreover,probe LFA and RCHO were successfully applied to the detection of H2 S in actual water samples and living cells.(2)Through Knoevenagel condensation reaction,we introduced the isophorone moiety into an aldehyde rhodamine derivative to synthesize a novel near-infrared xanthene-based fluorophore(RHI-OH)with "D-π-A" structure and large Stokes shift(155 nm).Using this fluorophore,we have developed two fluorescent probes RHI and RHS for the detection of Cys and pd0,respectively.The response mechanism of probe RHI was based on Cys induced Michael addition-intramolecular cyclization reaction mechanism.After reaction with Cys,the acrylate group of the probe RHI was selectively removed and the fluorescence intensity enhanced significantly.The probe exhibited high sensitivity and selectivity and large Stokes shift for Cys detection.The detection limit of probe RHI towards Cys was 173 n M.Moreover,the probe could be used for quantitative detection of Cys in environmental water samples and milk samples and fluorescence imaging of Cys in living cells.Based on the Tsuji-Trost reaction strategy,probe RHS was constructed by using allyl carbonate group and fluorophore RHI-OH.The probe possessed many advantages of Pd0 detection,such as high selectivity,high sensitivity(140 n M),large Stokes shift(155 nm)and rapid response(20 min).The probe RHS could be applied to the detection of Pd0 in environmental water samples and living cells.(3)The fluorescent probe RANS with near infrared emission was designed and synthesized for detecting Hg2+ by using thiosemicarbazone as the recognition site of Hg2+.After reaction with Hg2+,Hg2+ induced the cyclization of thiosemicarbazone to produce 1,3,4-oxadiazole,which corresponding to the significant enhancement of fluorescence intensity.The color of the reaction solutions changed significantly(from colorless to light green),which indicating that Hg2+ could be detected with the naked eyes.The probe RANS performed ultrafast response to Hg2+(120 s),and the detection limit was as low as 19 n M.In addition,we have used the probe RANS to complete the quantitative detection of Hg2+ in actual water samples and the fluorescence imaging of Hg2+ in living cells.(4)Taking advantage of the dual nucleophilic properties of N2H4,a novel xanthene-based fluorescent probe RHAF for the detection of N2H4 with long wavelength emission was successfully designed and synthesized by using levulinate ester moiety as the specific reaction site of N2H4.In the presence of various amines,the probe RHAF could detect N2H4 with high sensitivity and selectivity,and the detection limit was as low as 51 n M.After reaction with N2H4,the color of the probe solution changed from colorless to light purple,which indicating that probe RHAF could be used for the naked-eyes detection of N2H4.In addition,the probe RHAF was successfully applied for quantitative detection of N2H4 in environmental water samples and fluorescence imaging of N2H4 in living cells.