Hg²⁺-selective Ratiometric Fluorescent Probe Based On Core-shell Structure

Mercury is widely used in daily life.For example,commonly used as thermos-metersand dental silver powders contain a large amount of inorganic mercury.It is well known that the analysis of trace amounts of mercury requires large-scale equipment and instruments atomic such as absorption spectroscopy?AAS?,inductively coupled plasma?ICP-MS?and mass spectrometry?MS?,which have poor detection timeliness.Therefore,it is particularly important to study fluorescent sensors that are simple,convenient,and inexpensive to detect mercury.The organic fluorescent probe method is an important method for detection heavy metal ions developed in recent years.The analysis speed is fast and the detection time is good.However,the detection selectivity of the organic fluorescent probe method is sensitive to the external environment,and most of the probes are not water-soluble,which greatly limits the practical application of the detection method.In response to the above problems,the paper modified two mercury ion probes that mutually fluorescent to the receptor to the two blocks of the block copolymer to improve the water solubility of the fluorescence detection system.The resonance energy transfer system formed by two mercury ion probes can effectively realize the ratiometric mercury ion detection,eliminate the environmental interference during the detection process,and improve the detection sensitivity.The main work includes three aspects,as follows:?1?Compound 1 was successful synthesis by Biginelli reaction,followed by bromination reaction and nucleophilic substitution reaction to synthesize fluorescent probe EPY.The fluorescence detection and UV-visible absorption test were used to investigate the optical detection performance of probe EPY on Hg²⁺ions.In acetic acid buffer solution(10 mM,pH3.6,?_ex=394 nm),the probe EPY has good selectivity and anti-interference for the detection of Hg²⁺ions,and the detection sensitivity is high and the detection limit reaches 0.098?M.At the same time,we found that EDTA ions have a significant enhancement to the fluorescence emission of the EPY-Hg²⁺complex and are highly resistant to interference.The fluorescent probe EPY exhibited a"ON-OFF-amplified ON"fluorescence phenomenon by adding Hg²⁺ions and EDTA.In order to understand the mechanism of fluorescent probe EPY recognition,we further utilized nuclear magnetic and mass spectrometry to demonstrate that it forms EPY-Hg²⁺complex and EPY-Hg²⁺-EDTA complex with Hg²⁺ion and EDTA ion in aqueous solution.?2?Chemical modification of acryloyl chloride to obtain compound 3,and synthesis of the double-bonded fluorescent probe EAM with compound 1 by bromination and amide reaction.The metal ion selectivity,anti-interference and detection sensitivity were investigated in a methanol-acetate buffer mixed solution(V:V,1:9,10 mM,pH 5,?_ex=396 nm).Fluorescent probe EAM also has a fluorescent response signal to mercury ions in an acidic environment,and shows good selectivity in the anti-interference test.The detection limit is 3.76?M.At the same time,the selectivity of the fluorescent probe EAM-Hg²⁺complex to anions was also studied.After adding EDTA,the fluorescence intensity of EAM-Hg²⁺was enhanced,and its recognition mechanism was discussed.?3?The amphiphilic block polymer-based ratio type fluorescent probe P?NIPAM-co-RhBHA?-b-P?MMA-co-EAM?was synthesized by a reversible addition-fragmentation chain transfer?RAFT?polymerization method.Among them,the resonance energy acceptor RhBHA is attached to the hydrophilic segment PNIPAM,and the resonance energy donor EAM is attached to the non-hydrophilic segment PMMA.The amphiphilic polymer P?N-isopropylacrylamide-co-RhBHA?-b-P?methyl methacrylate-co-EAM?can self-assemble in an aqueous solution to form a core-shell structure.In the mercury ion fluorescence spectroscopy test,it was found that the ratiometric fluorescent probe based on FRET mechanism can significantly improve the selectivity and anti-interference of Hg²⁺ions,and the detection sensitivity reaches 0.012?M.At the same time,the P?NIPAM-co-RhBHA?-b-P?MMA-co-EAM?has metal selectivity to Cu²⁺ions and the detection sensitivity is 0.064?M.