| Due to the advantages of monochromaticity,directivity,high power and non-contacting machining method,laser was widely applied in the national defense,aerospace,transportation,biological medicine,artificial intelligence,quantum communication and so on.In the field of micro/nano fabrication that needs high processing precision,pulsed laser especially ultrafast laser has the advanteges of interacting with materials in ultrashort time range and low heat effect,high processing precision with sample equipments,easy fabrication of three dimensional materials.As the development of national economy,environmental issues are appearing and becoming serious ecological problems,especially for some trace amount of high poisonous and harmful substances,such as heavy metal pollution,neurotoxin and so on.Surface enhanced Raman spectroscopy/scattering(SERS)was found in last century and has very low detection limit.To date,the surface enhanced Raman spectroscopy technique faces two maim barriers.The first one is the enhancement that should be improved and the second one is the worse repeatability or stability To break through the barriers,the processing precision in nanoscale should be researched.In other words,the controllable size and morphology nanostructures should be studied in order to increase the“hot spot”area.In addition,fabricating the periodic structure is essenstial to improve the uniformity of substrates.In this paper,the laser interference lithography and laser induced periodic surface structure are proposed and applied in surface enhanced Raman spectroscopy substrate fabrication.Firstly,the silver nanoparticles periodic structure was generated by ultraviolet nanosecond laser interference lithography and the performances of SERS substrates with and without laser processed were compared.Silver nanoparticles was synthesized by wet chemical method and the mean size was 50 nanometers.The silver nanoparticle film was deposited by solution evaporation method and its thickness could be adjusted by adding ascorbic acid.The optical properties of silver nanoparticle film and the influence of laser on silver nanoparticle film were studied.By studying the influence of laser processing on silver nanoparticle for SERS enhancement,the shape of silver nanoparticles shape determines the performance of SERS enhancement.By testing the rhodamine B,the SERS enhancement factor was 10~6 which was an order of magnitude higher than SERS substrate without laser processing.Based on the results of last section,different morphology of periodic nanoparticle structure was fabricated by controlled photon reduction.The silver precursor film composed of silver nitrate and polyvinylpyrrolidone was spin-coated on the substrate,and irradiated by laser interference lithography to generate periodic structure.The morphology of structure was controlled by subsequent violet and red light irradiation,which results in nanospheres and nanoplates periodic structures.The growth mechanism of nanoparticles induced by lights was discussed,which demonstrated that the nanoparticle'shape was mainly determined by local surface plasmon resonance.At the last of this section,the performances of two different morphologies of SERS substrates were compared by testing three different molecules(naproxen,rhodamine B and arsenate).All of the results demonstrated that enhancement factor of nanoplate were higher than nanosphere.The enhancement factor of naproxen is 10~5,R6G is higher than 10~6,and arsenate is as high as 10~9.In the fourth chapter,copper structure was fabricated by laser reduction assisted direct writing.As the copper source was copper salt solution instead of copper oxide,the fabricated copper structure is pure than the other works.The influence of laser parameters on copper structure was studied and the tempreture profile was simulated by finite element analysis.At last,the promising application of wearable electronic device basedon the copper structure was illustrated.After studying of SERS substrate,a real-time on line SERS microfluidic chip system was designed and developed.SERS microfluidic chip was fabricated by all-femtosecond-laser-processing,and microchannel was prepared by femtosecond laser assisted chemical etching.The metal film inside the microchannel was generated by electroless metal plating and demonstrated that the polyvinylpyrrolidone can reduce the roughness of metal film.The 2D periodic nanostructure on metal film was induced by femtosecond laser.The period of nanostructure was approximately quarter of laser wavelength,which was smaller than diffraction limit.The enhancement factor of SERS microfluidic chip was higher than 10~8 by testing rhodanmine 6G,and the relative standard deviation was lower than 10%.At last,in order to demonstrate the application of SERS microfluidic chip,the heavy metal ion(Cd)in crystal violet solution was detected in real-time.The detection limit of Cd was 10 ppb with short response time,which demonstrated the SERS microfluidic chip was reliable,stable and sensitive.In the last part of this paper,a 3D SERS substrate was explored.The vertical silicon nanowires was the backbone of 3D SERS substrate,which generated by metal assisted chemical etching.The silver nanoparticles decorated on the silicon nanowires to form3D SERS substrate.In detail,the influence of each composition of etching solution on silicon etching was study and analyzed.The length,separation distance of nanowires was explored and controlled by changing the composition of etching solution.Silver nanoparticles was synthesized by photon reduction and decorated on silicon nanowires by self-assembling.At last,the performance of 3D SERS substrate proposed by testing rhodanmine 6G and the enhancement factor was higher than 2D SERS substrate. |
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