Preparation Of Noble Metal Nanostructure Array Substrates And Study On Surface Enhancement Spectrum Properties

Studies have shown that the free electrons on the surface of the noble metal nanostructure substrate can interact with the incident photons to form an electronic oscillation mode under the excitation of the external light field.In particular,when the frequency of the input photons matches the frequency of the electronic oscillation,surface plasmon resonance is occurred,and strong local electromagnetic field enhancement is generated to effectively amplify the optical signal of the probe molecules near the substrate.Researchers not only use physical or chemical methods to prepare metal nanostructured substrates with different morphologies and sizes,but also various strategies have been proposed to achieve precise manipulation of the nanostructure"Gap",thereby effectively regulating the spectral signals of the probe molecules.The surface plasmon-enhanced spectroscopy of noble metal nanostructured substrates has important potential applications in spectral sensing,bioanalysis and medical imaging,so it has important research significance.In this paper,metal nanostructured substrates were prepared by evaporation and interface self-assembly methods,and the effects of self-assembled metal nanostructured substrates on surface-enhanced Raman scattering(SERS)were investigated.Based on the principle of laser spectroscopy,the regulation of substrate morphology changes on the Raman spectrum of probe molecules was studied and analyzed.Based on the Finite element method(FEM),the local electromagnetic field distribution of the metal nanostructured substrate was calculated by COMSOL software.The role of local electromagnetic field enhancement in surface enhanced Raman scattering was discussed and analyzed.The experimental results show that the self-assembled metal nanostructure substrate exhibits good SERS activity under specific excitation conditions.In this paper,the electromagnetic"hot spots"distribution of the substrate was controlled by changing the morphology and dimension of the substrate,and the SERS enhancement effect of the enhanced substrate after the introduction of graphene was analyzed.Its main work is as follows:1.The effects of vertical array morphology changes of self-assembled gold nanorods(GNRs)on surface-enhanced Raman scattering were studied,and the sensitivity,repeatability and stability of substrate-enhanced Raman activity were systematically investigated.The GNRs colloidal solution was prepared by the“seed method”,and the vertical array of GNRs was obtained on the surface of the silicon wafer by evaporation self-assembly.The morphology of the array was regulated by changing the soaking time of the substrate in the probe molecule solution.It was found that when the substrate soaking time was 30 minutes,the best SERS signal was obtained,and the Raman enhancement factor of the substrate was 9.65×10~5 times.Based on the optimal soaking time,the sensitivity,repeatability and stability of the substrate were investigated.The effect of the change of the local electromagnetic field on the Raman scattering of the molecule was analyzed by the simulation calculation.The simulation result is consistent with the experimental results.2.Based on the above substrate preparation,the experiment utilizes PMMA polymer protection-etching method to transfer two-dimensional material monolayer graphene on the surface of the GNRs vertical array.The SERS effect of Rh6G molecules adsorbed on the surface of G/GNRs vertical array hybrid substrate was studied.The Raman spectroscopy results show that the G/GNRs vertical array hybrid substrate can greatly improve the Raman scattering signal of Rh6G compared with the bare GNRs vertical array,and the optimal enhancement factor is about 7.9×10~8.According to the theoretical model of electromagnetic enhancement,the surface plasmon coupling effect generated between adjacent nanoparticles can effectively enhance the Raman signal of molecule.In addition,both experimental and theoretical calculations show that the excellent physical and chemical properties of graphene play a positive role in enhancing the Raman activity of the substrate.3.The enhancement effect of flexible self-assembled three-dimensional substrate gold nanoparticles/graphene/gold nanoparticles on Raman scattering of probe molecules was investigated.The gold nanoparticle colloidal solution was prepared by"boiling method",and the AuNPs film was prepared in the the liquid/liquid boundary layer by the characteristic of oil-water incompatibility.The AuNPs/G/AuNPs flexible substrate was obtained on the polyethylene film by pulling and transferring.Compared with the control group,the AuNPs/G/AuNPs substrate can effectively enhance the Raman signal of the Rh6G molecule and the optimal Raman enhancement factor of the substrate is about1.6×10~6.According to the theory of electromagnetic enhancement,the prepared three-dimensional substrate can provide denser electromagnetic"hot spots"distribution.The excellent physical and chemical properties of graphene can not only effectively enrich the target molecule,but also provide additional chemical enhancement.Furthermore,the experimental results show that the flexible substrate can also effectively detect the pesticide molecule(thiram)Raman signal on the surface of orange,which provides an experimental basis for further promotion of the flexible substrate in the fields of food safety and environmental detection engineering applications.