Construction Of Core-shell Fluorescence Probe And The Application In Analysis And Detection

Core-shell structure nanomaterials integrate the characteristics of inorganic,organic and nanomaterials,and excellent performance can be obtained by controlling core-shell properties.Core-shell structure nanomaterials have been widely applied in fluorescence detection and other fields.Construction of ratio fluorescence probe with core-shell structure strategy can not only maintain good light stability and strong fluorescence intensity of the reference signal,but also effectively combine with the response signal through functionalization,so as to realize the ratio fluorescence detection.We systematically studied the construction of core-shell fluorescence probe and its application in analysis and detection.The energy transfer mechanism between detected substances and response signals has been investigated.The detail works including following three parts:（1）The first part of the work is to prepare carbon points（CDs）by hydrothermal method using L-arginine as carbon source.A CDs@Si O₂-Tb core-shell ratio fluorescence probe containing two emission centers was constructed by coating CDs with silica and connecting with rare earth Tb³⁺through surface carboxylation.Silica is chemically inert and light permeable,and can effectively improve the water dispersion of materials.The emission of CDs was at 340 nm,while the strongest emission of Tb³⁺was at 544 nm.Due to the coating of silica,CDs can be used as a reference signal stably,which is not interfered by the external environment.2,6-pyridine dicarboxylic acid（DPA）as a biomarker of Bacillus anthracis,can sensitize the fluorescence of Tb³⁺effectively by antenna effect,thus achieving the ratio fluorescence detection of DPA.In addition,with the increase of DPA,the system changed from colorless to green under the irradiation of 254 nm UV lamp,so visual detection can be realized.The experimental results showed that there was a good linear relationship between the DPA concentration and the fluorescence emission intensity ratio(I₅₄₄/I₃₄₀)in the detection range of 0-2μM,and the limit of detection（LOD）was 10.2 n M.（2）In the second part,fluorescein（FL）molecules were doped in silica nanoparticles,and rare-earth Eu³⁺was introduced after surface carboxylation to synthesize the FL@Si O₂-Eu ratio fluorescence probe.The green emission of FL at 515 nm was used as the reference signal,and the red emission of Eu³⁺at 613 nm was used as the response signal.The sensitive detection of DPA was realized by the fluorescence enhancement of Eu³⁺by DPA sensitization.In addition,under the irradiation of 254 nm UV lamp,the probe system changed from green to red with the addition of DPA,which can realize visual detection.The results showed that the DPA concentration had a good linear relationship with the fluorescence emission ratio(I₆₁₃/I₅₁₅)in the detection range of 0-4μM,and the limit of detection（LOD）was 0.4 n M.（3）In the third part,fluorescein（FL）molecules were doped into silica nanoparticles,and the surface of silica was hydroxylated and then carboxylated.Then,the FL@Si O₂-Eu/His ratio fluorescent probe was synthesized by using L-histidine（L-His）to partially replace the carboxyl group on the surface and connecting with rare-earth Eu³⁺.The probe can sensitively detect the tryptophan chiral molecules of D-Trp and L-Trp through introducing the chiral center.Tryptophan can effectively quench the fluorescence of Eu³⁺due to the energy transfer effect.As the interaction between analyte and chiral recognition site is different,the quenching efficiency and quenching rate of tryptophan enantiomers for Eu³⁺are different.The results showed that the fluorescence intensity ratio(I₆₁₃/I₅₁₅)had a negative linear relationship with the tryptophan enantiomers,and the LOD was 1.0μM（L-Trp）and 1.3μM（D-Trp）,respectively.The probe also showed good results for the detection of tryptophan enantiomers in tap water and bovine serum.In summary,a ratio fluorescence probe based on core-shell structure was constructed and applied in the detection of biomarkers of Bacillus anthracis and tryptophan chiral molecules.The fluorescence probe can specifically identify the analyte sensitively and selectively,and can also realize the visual detection.At the same time,the detection results are good in actual bovine serum and tap water samples.This work provides a new idea for the construction of new type fluorescence sensor.