Preparation Of Core-shell Nanoparticle Tag And Application In Ion Detection

Core-shell nanoparticles have been focused on due to their remarkable adjustable physical and chemical properties.Due to its unique characteristics of local surface plasmon resonance(LSPR),core-shell nanomaterials are widely used in surface enhanced vibrational spectroscopy.By adjusting its structural components,the performance of biosensors can be effectively improved for the detection of heavy metal ions.On this basis,several core-shell nanoparticles are designed to analyze and detect heavy metal ions through various detection strategies.The specific works areas follows:(1)A surface-enhanced Raman scattering(SERS)probe with bulk phase encoding is designed,in which polymethylmethacrylate(PMMA)is used as a thin and pinhole-free Raman active polymer.This strategy is different from the sub-monolayer SERS probes using single molecules as signals,because the PMMA bulk phase has a pinhole-free and highly cross-linked structure.The bulk phase applied as the shell of the probe,not only provides ideal protection for the Au NPs as signal amplifiers inside,but also avoids the unfavorable treatment during the process of modifying the protective shell,which core material and the signal molecules on its surface should damage.In addition,the thin bulk phase keep the signal molecules in the long-range electromagnetic field of Au nanoparticles,which can make full use of the electromagnetic field enhancement effect of Au nanoparticles to increase the signal strength.Therefore,the SERS probe can provide a strong,stable and high-purity SERS signal for the detection of Hg²⁺ions,with a detection limit of 3.2×10^-10M,which is better than many traditional SERS probes.(2)Based on the previous chapter,the polystyrene(PS)with stronger Raman signal is selected as the main signal shell to wrap the Au NPs.After linking PS to Au NPs,it is difficult to modify for biosensing detection by no other active group of PS.Therefore,acrylic acid is added to introduce active carboxyl groups in the PS layer on the surface of Au NPs,during the synthesis process of PS via emulsion method.This strategy could effectively combine PS with amino groups,carboxyl groups and sulfhydryl groups,which is beneficial for the further improvement of the Au@PS probes application in biosensing.The DNA modified with amino group is grafted on the surface of Au@PS NPs and the Au@PS-DNA probe is obtained.This probe shows good selectivity and excellent sensitivity as the specific binding between DNA and Hg²⁺,which could form T-Hg²⁺-T and enable the Au@PS-DNA probe bind with DNA-containing substrate.The detection limit is 0.12 n M.We believe that the Au@PS SERS probe could play a greater role in the actual detection of molecules or ions in the future.(3)By the detection of heavy metal ions in organisms,it is difficult to distinguish the detection signal due to the SERS signal of many materials overlaps with the signal in the cell.In order to solve this problem,it is necessary to develop a SERS with a stable detection signal in the silent zone for the detection of heavy metal ions in organisms.Here,a bimetal embedded SERS probe Au-EDAT@Ag probe with quiet zone signal was prepared.This probe is based on the specific binding property of cysteine to Cu²⁺,which was used to"aggregate"the SERS sensing.Thus,the Cu²⁺in the solution was effectively detected,and the detection limit could reach 0.85n M.The Au-EDAT@Ag SERS probe is applied to the detection of Cu²⁺in cell lysate and shows good results.Therefore,the Au-EDAT@Ag-cys SERS sensor system has remarkable potential for the detection of Cu²⁺in a variety of organisms.(4)An Au@PB core-shell nanostructure material with Au NPs as the surface plasmon enhanced core and Prussian blue(PB)as the shell,is designed and synthesized.It is applied as SERS probe to selectively capture Cs⁺ions.The PB assembled on the surface of Au NPs provides a large number of Raman signal molecules.As the number of Raman signal molecules increases,the signal intensity of the probe is effectively increased.The PB shell formed by C?N bridges has a lattice structure.The cage size in the lattice could be used for the selective adsorption of Cs⁺ions.The Raman vibration peak will change when Cs⁺are embedded in PB,therefore cesium ions can be effectively detected by the Au@PB probe in water.(5)A highly sensitive and selective metal-enhanced fluorescent probe for the detection of Hg²⁺ions is developed via fixing the"turn-on"fluorescent probe on Au@Si O₂NPs.The detection limit is 0.11n M,which is far lower than the allowable detection limit of Environmental Protection Agency(EPA)for Hg²⁺ions in drinking water(<10 n M).The color change of the fluorescent probe could be observed with naked eyes under certain solution conditions.A test strip for the visual detection of Hg²⁺ion is prepared by this Au@Si O₂NPs.In addition,it is applied to the detection of Hg²⁺ions in actual water,and the detection of Hg²⁺ions in biological systems through fluorescence imaging of cells and living bodies.These results indicate that the fluorescently labeled Au@Si O₂probe is feasible for the actual detection of Hg²⁺ions in the environment,cells and living bodies.