Design Of A New 3D Noble Metal SERS Substrate And Its Trace Detection Application

Surface enhanced Raman spectroscopy(SERS)can identify the characteristic information of molecules,and has huge application space in the fields of molecular recognition,microscopic imaging,and environmental pollutant detection.Due to the scale-dependent nature of surface-enhanced Raman scattering effect of nanostructures,the intensity and number of hot spots in one-dimensional and twodimensional substrates are limited,and it is difficult to increase the measurement concentration limit when used in trace detection of substances.In order to solve this problem,this paper adopts modified and double-layer design ideas for gold and silver nanostructures to improve the surface enhancement Raman detection limit of substrates.(1)The silver nanoparticle array was prepared on the quartz substrate by thermal rapid annealing method.SEM results showed that the average diameter of silver nanoparticles was 87.9±30.7 nm.The SERS effect of this substrate was analyzed by Raman experiment and electromagnetic field simulation.Gentian violet was used as the probe molecule.The results of SERS experiments show that silver nanoparticle arrays can be used to detect gentian violet solution at a concentration of 10’5 mol/L,which is 4 orders of magnitude higher than that of the control sample.This is attributed to the local surface plasmon effect of silver nanoparticles.After coating modification by polyvinyl alcohol(PVA),the silver nanoarray substrate can be used to detect gentian violet solution at a concentration of 10-8 mol/L,which is 3 orders of magnitude higher than the detection limit before coating,mainly due to the quenching of gentian violet molecular fluorescence by PVA coating.(2)On the basis of the preparation of gold nanoparticle array by thermal rapid annealing method,silver nanoparticles were grown on gold nanoarrays by vacuum thermal evaporation method evaporation copper film and chemical displacement in silver nitrate solution to construct three-dimensional gold and silver structures(Au@Ag).The experimental results of SEM and EDS confirmed the formation of threedimensional structure Au@Ag.Au@Ag substrate can be used to detect malachite green solution at a concentration of 10-8 mol/L,and the detection limit is 4 orders of magnitude higher than that of a monolayer gold nano substrate and 3 orders of magnitude higher than that of a monolayer silver nano substrate.This is mainly due to the larger absorption coefficient,wider absorption peak,and stronger local surface plasmon effect in the Au@Ag substrate absorption curve.The calculation results of electric field distribution show that there is plasmon coupling between gold and silver pillars in the Au@Ag threedimensional structure.The number of hot spots generated increases significantly as well as their enhanced intensity.The results of this paper provide a new design idea for the development of new,efficient and stable three-dimensional SERS substrates,which can be used in the fields of trace detection of water quality and solar energy utilization.