SERS Sensors Based On Light Trapping Plasmonic Micro/Nano Structures And The Applications

In recent years,metallic micro/nano structures with sub-wavelength size have attracted much attention in optical design and management due to the surface plasmon resonance and coupling properties.Under the irradiation of light,the optical energy density and the local electromagnetic field of the nano area on the surface of metallic micro/nano structures are greatly enhanced due to the localized surface plasmon resonance(LSPR).The light.trapping structures can effectively increase the path of light,thus increasing the optical path.Therefore,as an efficient light management structure,it is widely used in solar cells.In the process of interaction between light and plasmonic micro/nano structures,light-trapping structures can effectively confine light to micro/nano structures,so as to further enhance.the interaction.Therefore,it can provide a better idea for the efficient interaction between light and micro/nano structures by changing the structure design to strengthen the photon capture and control.LSPR effect has very high application value in many research fields,including biological fluorescent labeling detection,surface enhanced Raman scattering(SERS)detection,photoelectric device preparation and so on.In this paper,we combine the light trapping effect with plasmonic micro/nano structures to enhance the utilization of light in plasmonic micro/nano structures,and further enhance the interaction between light and plasmonic structures to stimulate more efficient LSPR.As a verification of the enhanced LSPR effect,the SERS sensors formed by the trapped plasmonic micro/nano structures are studied and analyzed.Through the design and preparation of three kinds of light trapping plasmonic micro/nano structures,after the analysis of their morphology and elements,the LSPR characteristics were studied.Finally,the light trapping plasmonic micro/nano structures were successfully applied to SERS sensors,and high performance SERS detection was realized.The main contents of this paper are as follows:(1)Preparation of trapped plasmonic nanostructuresThree kinds of trapped plasmonic micro/nano structures were prepared,which were silver coated parylene C coated carbon nanoparticles(Ag-PC@CNPs),3D Au/Ag NCF nanohybrids and Au nanoparticles coated nanofiber forest with a back reflector(Au@NF-BR).Scanning electron microscopy(SEM),transmission electron microscopy(TEM),Energy dispersive X-ray spectroscopy(EDX),XRD and other analysis methods were used to characterize the structure morphology.The specific distribution of light trapping micro/nano structures and metallic nano structures was analyzed,which provided the basis for the later LSPR characteristics research and SERS detection.(2)LSPR properties of trapped plasmonic nanostructures In this paper,the LSPR characteristics of three kinds of trapped plasmonic micro/nano structures are studied and analyzed.The theoretical simulation and optical absorption test are carried out,respectively.The high absorption capacity of the three structures is tested and verified,which shows that the three structures can make efficient use of light.With the increase of light absorption,the interaction between light and plasmonic micro/nano structures is also increased,which further enhances the LSPR characteristics.(3)Influence of wetting property of trapped plasmonic micro/nano structures for molecular enrichment The substrates based on Ag-PC@CNPs exhibits superhydrophobic properties.When analyte droplets roll over the substrate,Ag-PC@CNPs can be picked by droplets and adsorbed into the droplets,thus forming self-concentrated structures with 3D "hot spots"in the droplet.The substrate of 3D Au/Ag NCF nanohybrids has superhydrophobic and high adhesion property,so the molecules can be further limited in the 3D Au/Ag NCF nanohybrids,and the double enrichment of the molecules in the metallic structures can be realized,which is of great significance for improving the SERS performance.The Au@NF-BR structures also have superhydrophobic property,which can enrich molecules by evaporation,and can also improve the SERS performance.The research on the wettability of the above three structures is of great significance to further improve the detection performance of SERS.(4)Performance of SERS sensor based on trapped plasmon micro nano structure The performances of the three kinds of sensors were analyzed.Through the detection of R6G,MG and other probe molecules with different concentrations,the detection range of SERS droplet sensor is 10-13 M to 10-5M,the detection limit is 10-13M,and the enhancement factor can reach 109.The detection range of 3D Au/Ag NCF nanohybrids is 10-15 M to 10-4 M,and its detection limit is as low as 10-15 M.The detection range of Au@NF-BR SERS substrate is 10-12 M to 10-5 M,and the detection limit is 10-12 M.The relative standard deviation of these substrates is less than 10%,so they can be used as devices for further practical applications.In addition,the stability of the three substrates was tested.The test results within 30 days show that the three substrates have good stability,which further shows the great potential of the three substrates in practical application.(5)Application of SERS sensor based on trapped plasmonic micro/nano structures in biochemical detection After analyzing the SERS performance of the three kinds of sensors,the application of these SERS sensors in biological and chemical molecular detection is studied.Because SERS droplet sensor is used to detect in liquid environment,it is far more mild for the detection of biological macromolecules.Finally,the concentration of 100?M,1?M,10nM,100pM and 1pM can be detected by the SERS droplet sensor.For SERS substrate of 3D Au/Ag NCF nanohybrids,the concentration of thiram ranged from 10-11M to 10-4M,and the detection limit of 10-11M was far lower than the maximum residue limit of national food safety standard GB2763-2019,so it has great potential for practical application of pesticide residues.Meanwhile,in the mixed solution of malachite green and thiram,two analytes can be detected very clearly,indicating that the substrate has good specificity.For the SERS substrate formed by the Au@NF-BR nanostructures,thiram were also detected,and 10-9 M to 10-6 M thiram was detected.In this paper,three kinds of SERS sensors based on different trapping plasmonic micro/nano structure have good performance,and have advantages in biochemical detection.These studies provide some research ideas and methods for the design and optimization of SERS sensors.