Preparation Of Silver Nano Scaffold Structure By Dynamic Shadowing Growth Method And It’s Optical Properties

With the improvement of living standards,some livelihood issues such as food safety,environmental pollution,biomedical testing and so on have gradually become hot topic.The micro-nano biochemical sensor based on localized surface plasmons exhibits effective detection capability.However,the key problem is to develop the micro-nano sensor devices with simple structure and high efficiency,because the performance of them is closely related to the design and preparation of its structure.In this thesis,silver nano-tripod（AgNT）structure with built-in high-density"hot spots"distribution was fabricated by combining theoretical calculation and experimental design.The effects of structural parameters on its absorption characteristics,circular dichroism and electric field enhancement performance were analyzed,and further it was used as a surface enhanced Raman scattering（SERS）sensor for the detection of food and environmental samples.The research content includes the following parts:1.The structure of AgNT was designed and its optical properties was calculated.By constructing the silver nanometer straight and tripod structure with the same total rod length and tilting angle,using the Finite-Difference Time-Domain method to simulate and compare the electric field enhancement performance of two structures.The length and inclination angle of the single folding rod were optimized in the simulation of the AgNT structure,and the influence of different structural parameters on its light absorption characteristics and electric field enhancement performance was calculated.The results show that the AgNT’s"hot spot"distribution is stronger than the silver straight nanorod structure.For AgNT structure,the absorbance and enhancement of the electric field are the best near the wavelength of 785 nm,when the single folding rod length is taken 350nm and the inclination angle is taken 72°2.The AgNT structure was prepared by the dynamic shadowing growth method.A vacuum electron beam evaporation coating system is used depending on the physical vapor deposition technology,and the structure parameters optimized by theoretical calculation are used to make the silver straight nanorods structure by setting the tilt angle of the sample stage.The sample stage of the azimuth angle is rotated counterclockwise twice to achieve the construction’s rotation and nano corner gap’s folding.The results show that when the tilting angle is 86°and the azimuth angle is 120°,the prepared structure would coincide with the theoretical calculation results,and its spatial structure parameters provide a basis for further theoretical calculations.3.The AgNT structure was used as a SERS sensor for food safety and environmental pollution detection.The probe molecules Rhodamine 6G and crystal violet molecules were used to characterize the best structure AgNT substrates for SERS performance,and they were applied to the actual spiked samples detection of methylviologen in river water,soil and fruit epidermis.The results of the study showed that the SERS enhancement factors of rhodamine 6G and crystal violet were both about 10⁷,detection limit of rhodamine 6G was 2.24×10^-8 M,and detection limit of crystal violet was 4.01×10^-8 M.When the concentration of rhodamine 6G and crystal violet solution is in the range of5×10^-8 M and 1×10^-5 M,they showed good linearity and exponential correlation,respectively,and the relative standard deviation is less than 5%.The detection limits of the AgNT structure for spiked methyl viologen in actual river water,soil and apple skin were 4.59 ppb,6.48 ppb and 5.14 ppb,respectively.4.Designed and prepared the regular polygonal silver nano scaffold（RP-Ag NS）structure and studied its optical properties.On the basis of the design and preparation of the tripod structure,by increasing the number of rotation and folding,more corner gaps were obtained,and the AgNT structure with a regular polygonal morphology under the top view angle was constructed.The effects of the number of rotation and folding on the absorption,circular dichroism and SERS performance of the RP-Ag NS structure were respectively explored.Both experimental and simulation results showed that when the total length of silver nanorods remains the same,when the number of folded silver nanorods is 6,the RP-Ag NS structure shows better electric field enhancement,absorption,circular dichroism and SERS performance.The AgNT prepared in this study has broad application prospects in SERS sensing,circular dichroism and light absorption,and may provide new ideas for the design and preparation of high-sensitivity micro-nano sensors.