The Fabrication And Investigation Of Multi-target Fluorescent Ratiometric Probes Based On Lariat Ether

Generally,low concentration of silver nano-materials can play an antibacterial role.When the concentration reaches a certain range,it will generate excessive hydrogen peroxide and silver ions which induce the body to undergo oxidative stress,eventually have an adverse effect on the body.However,the mechanism and behavior of silver as antimicobal agent is still ambiguous.To evaluate the risk of silver to ecology and human being,it is necessary to develop multi-target fluorescent probe to connect the fluctuation of the species with the exposure to silver production in vivo and in vitro.Herein,there are three kinds of ratiometric fluorescent probe fabricated based on lariat ether which undergoes Intramolecular Charge Transfer process and phenyl borate group as H₂O₂responsive site.Thus,the main contents of this thesis are organized as follows:（1）Intramolecular charge transfer conjugation system was constructed with pyridine armed lariat ether,a silver ion complex group,as charge acceptor and n-phenylcarbazole as charge donor.The lipophilicity of carbazole groups can enhance the hydrophobic effect of molecules in aqueous medium and form molecular aggregates.With the increase of the proportion of water in the mixed solvent,the molecule showed an obvious Tyndall phenomenon,and the fluorescence emission peak showed a red shift first and then a blue shift.In the medium of THF-H₂O（φ（H₂O）=87%）,the molecular aggregate presents a weak fluorescence emission peak at 428 nm.With the increase of Ag⁺concentration in the solution,the emission peak of Ag⁺complex at 498 nm gradually increases.The sensor molecular aggregate can realize proportional fluorescence detection of Ag⁺,and the detection limit is 0.076μM。The proportional signal of the sensor has a good linear relationship with 0-0.7μM Ag⁺.（2）To improve the emission property of EB（fluorescence quantum yield and fluorescence emission wavelength）,the terminal donor groups was tailed to Triphenylamine moiety.In the THF-H₂O（φ（H₂O）=86%）system,the probe molecule FB can achieve specific recognition of Ag⁺.Upon addition of Ag⁺,its fluorescence emission peak is red shifted from 467 nm to 519 nm,exhibiting the characteristics of ratio detection.The probe could detect Ag⁺with high selectivity and sensitivity in aqueous solutions and has an excellent linear relationship for Ag⁺detection of 0-3μM,with a detection limit of 0.136μM.（3）Taking the advantage of lariat ether as the Ag⁺receptor and phenylbutyrate as the H₂O₂targeted group,a multi-target fluorescent probe FBHP with the feature of ratiometricity has been envisaged.In the DMSO-PBS（10 m M,p H=7.4,φ（DMSO）=10%）solution,the probe sequentially detected H₂O₂and Ag⁺.In the presence of H₂O₂,the fluorescent emission peak showed an evident blue shift,subsequently addition of silver induced a remarkable redshift.Furthermore,the stepwise red-blue-yellow fluorescent color changes were also observed in naked eyes.Thus the multi-mode and multi-target probe achieves specific stepwise response to H₂O₂and Ag⁺in aqueous solutions,with detection limits of 0.056μM and 0.175μM,respectively.