The Applications Of Core-Shell Metal Nanoparticles In Quantitative SERS And Surface Luminescence Analysis

Surface enhanced Raman spectroscopy(SERS)and plasmon enhanced fluorescence spectroscopy(PEF)have ultra-high surface sensitivity as low as single molecule level.When the metal surface is irradiated by light,it will produce plasmon a resonance effect,which confines the visible light photons to the near-field in the sub-wavelength range.The enhanced local electromagnetic field will amplify the signal of Raman or fluorescence molecules on the metal surface,and the enhanced electromagnetic field intensity will weaken with the increase of distance.So,the intensity of the enhanced Raman and fluorescence signals depends on the material,morphology,size and distance between the probe and the metal.In 2010,our research group developed shell-isolated nanoparticles enhanced Raman spectroscopy(SHINERS)technology to solve the two problems of SERS materials and the universality of morphology,and later developed other shell-isolated nanoparticles to match the blue and green light excitation.Referring to the coupling mode of SHINERS technology,we improved the surface plasmon enhancement ability,and realized the Raman signal,dye molecule and quantum dots,MOS2,phosphorescence and so on.We hope that this method can be applied to the enhancement of all luminescent molecules,especially the weak luminescent molecules,such as metal nanoclusters and upconversion luminescent nanoparticles.Quantitative analysis is still one of the biggest challenges for the application of SERS technology.Using internal standard molecule(IS)can solve the problem of signal fluctuation and improve the accuracy of the method.The core-shell structure of shell isolated nanoparticle is a good substrate,IS can only be assembled between the core and shell or on the SiO2 shell.Therefore,it is more convenient and low-cost to replace the shell with Raman signal of a molecule located in the silent region.In order to further extend the work of our group,this paper bases on the application of core-shell nanoparticles enhanced Raman spectrum and fluorescence spectrum,three different core-shell nanoparticles were synthesized according to the different application filed,further expanding the application scope of core-shell nanoparticles enhanced Raman and fluorescence spectrum.The main research contents of this paper are as follows:1.We synthesized the core-shell structure nanoparticles(Au@PB NPs)with thin-shell Prussian blue coated onto the surface of gold nanoparticles,in which the PB shell showed a strong Raman vibration signal at 2155 cm-1.Different from other internal standard probes,the PB band is located at the Raman silent region,which greatly reduces the possibility of signal overlap and interference to analyte signal.It is suitable for the quantitative analysis of SERS of a complex system as an internal standard.In addition,Au@PB NPs are not affected by photobleaching or photoquenching because of its stable and reliable signal.Based on the core-shell structure of Au@PB NPs,the strong electromagnetic field of the core metal nanoparticles is used to enhance the Raman signal of the adsorbed molecules on the surface of the particles,and the PB shell is used as the Raman IS to correct the signal fluctuation caused by the uneven hot spots on the SERS substrate and the test conditions.The concentrations of crystal violet(CV)and dopamine(DA)in lake water and serum were measured.Experiments show that the core-shell nanoparticles can be developed into a simple,fast,free-label,low-cost,stable,accurate and universal enhanced substrate for SERS quantitative analysis,which has potential application in the actual complex system.2.We have developed a method of shell-isolated silver nanoparticles(Ag SHINs)to enhance metal nanoclusters(NCs)luminescence.Based on the strong coupling mode of Ag SHINs-NCs-Ag film,the Ag film and NCs are separated by a 2 nm isolation layer,forming an Ag nanoantenna platform,which greatly enhances the emission intensity of NCs.The versatility of the platform is examined by using various NCs.By tuning the Ag SHIN shell thickness,the coupling mode between SHINs and the NCs could be tuned,with maximum average enhancements for the[Au7Ag8(C?CtBu)12]+NCs and DNA-template Ag(DNA-Ag)NCs platforms found to be 231-fold and 153-fold,respectively.Using the platform of Ag SHINs to enhance the fluorescence of DNA-Ag NCs to detect target DNA,we further investigated its potential applications in biological interface analysis.The results show that the method of enhancing the luminescence of metal nanoclusters has potential for interface sensing analysis.3.Metal-insulator-metal gap plasmon structure can significantly enhance the luminescent intensity of upconversion luminescent nanoparticles(UCNPs).The bottom metal is the gold film,the isolation layer is the SiO2 layer,the upper metal is the core-shell nanoparticles(Au NRs@SiO2),to explore the influence of different SiO2 shell thickness on the surface enhanced luminescence effect of UCNPs.At the same time,the Au NRs with different localized surface plasmon resonance(LSPR)peaks were prepared,to explore the influence of the coupling degree between LSPR of Au NRs@SiO2 and excitation wavelength and emission wavelength of UCNPs on the surface-enhanced luminescence effect of UCNPs.