Metal Enhanced Fluorescence Effect And Application Of Noble Metal@Intelligent Core-shell Microgels

At present,the use of metal fluorescence enhancement?MEF?and fluorescence resonance energy transfer?FRET?to build fluorescent sensors has become a hot research topic.Some heavy metal ions can be detected with fluorescent probes that were assembled by noble metals and fluorescent substances.It is found that the distance between the metal nanoparticles and the fluorescent substance may be an important factor affecting the fluorescence intensity.The intelligent polymer is an excellent barrier material because of its special environmental stimulus response.Thus,core-shell noble metal@smart polymer microgels are prepared and studied.In this paper,the MEF and FRET effect of the noble metal on the fluorescent substance?RhBHA,CdSe QDs,FITC?were used to construct the fluorescent probe which could detect the heavy metal ions and sugar.The effects of the distance between the noble metal and the fluorescent substance on MEF effect were studied.The main contents of this paper and the research results are as follows:1.AgNPs with uniform morphology,good dispersion and controlled particle size were prepared by seed growth method using sodium citrate as a reducing and stabilize agent.AgNP@P?NIPAM-co-RhBHA?was prepared by surface graft polymerization using isopropylacrylamide?NIPAM?and acryloyl isothiocyanate rhodamine hydrazide?RhBHA?as monomer.The effect of AgNP on RhBHA fluorescence at different concentrations of Hg²⁺ was studied.It is found that microgels with 45 nm AgNP core has a good MEF effect on RhBHA,and this MEF effect is temperature sensitive.The prepared core-shell microgel was used as fluorescent probe for Hg²⁺ assay.Under the optimal experimental condition,the Ag45@P?N-R?microgel exhibited the best fluorescence enhancement effect and better selectivity for Hg²⁺ relative to other metal ions.The detection limit is 97 nM.This fluorescent probe based on MEF will be explored the potential applications in detecting heavy metal ions.2.AgNP@PNIPAM microgels with different sizes of AgNPs and different thickness PNIPAM shell were prepared and CdSe QDs were assembled on the microgels surface by hydrogen bonding.The effects of different sizes of silver nanoparticles and polymer shell thickness on the fluorescence properties of CdSe QDs were studied.The results showed that Ag28@PNIPAM with a thickness of 10 nm and Ag45@PNIPAM with the thickness of 35 nm exhibited the best 5.3,and 5.1 times MEF effect on CdSe QDs,respectively.On the base of Cu²⁺-induced the weakening of fluorescence enhancement,the signal response of AgNP@PNIPAM-CdSe QDs against Cu²⁺concentration is linear over arrange from 0 to 500 nM.The detection limit is 3.5 nM,which is lower than the maximum limits guided by the United States Environmental Protection Agency as well as that permitted by the World Health Organization.In addition,this fluorescence probe showed good selectivity and sensitivity.3.FITC-modified PDA microspheres were obtained by spontaneous oxidation polymerization of dopamine?DA?with fluorescein isothiocyanate?FITC?under alkaline conditions.Because Au?III?can be reduced to AuNPs due to o-phenolic groups in PDA,and then the fluorescence of FITC can quenched by AuNPs through FRET,PDA-FITC system can be used as a fluorescent probe to selectively detect Au?III?.The fluorescence intensity against Au?III?concentration is linear in the range of 0-30 ?M,and the detection limit is 40 nM.Moreover,the PDA-FITC-GOx composite.It can be used as glucose assay.The decrease of fluorescence intensity presents a linear relationship with glucose concentration in the range from 0 to 80 mM with a detection limit of 23 nM.This fluorescent probe may have promising applications in high sensitive detecting Au?III?and glucose.