Polymer Assisted Fabrication Of Novel Metallic Ordered Micro/Nanostructures And Their Optical Sensing

Plasmonic metallic nanostructures have obtained great attention by researchers owing for their outstanding performance in concentrating light at the interface between metal and dielectric materials,which led their promising application in sensing,display device preparation and photovoltaics.Due to the metallic nanostructure's enhanced electric field around its surface is extremely sensitive to its dielectric environment's refractive index change,it can be applied in refractometric sensing.Composition and shape distinguished metallic nanostructured surface are destined to exhibit totally different performance in sensing.Noble metals have inert activity,high resonant intensity,simplicity in modification and high biocompatibility.Hence they are excellent material candidates for plasmonic sensing.As for the structure's shape design,3D plasmonic nanostructures always have better sensing performance compared with their 2D counterparts according to previous reports.Therefore we decided to design the metallic nanostructured surface as 3D nanostructure.Nowadays most reported fabrication approaches for metallic nanostructured surface are based on focus ion beam lithography or electron beam lithography because of their flexibility and precision in structure design and accomplishment.However,they also suffer the inevitable problems of high equipment requirement,low throughput and inability for3D metallic nanostructures.Therefore figuring out a solution for fabricating goal nanostructures with high efficiency as well as low consumption is significantly important.Colloidal lithography takes the ordered self-assembly of colloidal crystal as a mask.Combining successive mask treatment and pattern transfer,it can obtain large area highly ordered and structural parameters highly tunable 2D or 3D metallic nanostructures.We employed polymer colloidal lithography in a flexible manner and achieved 3D metallic nanoring,deep silver nanowell,and deep elliptical silver nanowell arrays'preparation and application in optical sensing and immunoassay.In the 2^nd chapter,we achieved large area orderly aligned 3D silver nanoring arrays by multistep polymer colloidal lithography combining metal deposition.Previously reported 2D metallic nanoring arrays'optical performance were always influenced by the substrate and 3D nanoring arrays'fabrication were mostly based on focus ion beam lithography,which required high consumption and provided rather low efficiency.We utilized the ring vacancy left on the top of silicon nanopillars after twice etching of polymer nanosphere and metal deposition to get shallow Au nanoring-silicon nanopillar arrays.The specific structural parameters of 3D-silver nanoring arrays could be facilely tuned by operating the etching conditions.Considering the optical and sensing performance,we optimized the structural parameters of 3D-silver nanoring arrays gradually and finally determined the best conditions for preparation.The optimized 3D-silver nanoring arrays'refractometric sensitivity reached 1105.8 nm/RIU,which was superior than most peer nanostructures'performance.They were also successfully applied in immunoassay.This fabrication approach as we described fulfilled the vacancy in fabrication of3D-silver nanoring arrays by colloidal lithography.The Au nanoring arrays on the top of Si nanopillar arrays were smartly etched to 3D-Si nanoring arrays and employed for the transformation of the structure:from 2D to 3D.This approach not only provided a brand-new method to build 3D nanostructures,but also improved the situation of merely using FIB to fabricate 3D metallic nanorings.In the 3^rd chapter,we combined polymer colloidal lithography with metal deposition to build large area highly ordered deep silver nanowell arrays to realize plasmonic sensing.Distinct from most previous reports of metallic nanohole arrays,we focused on the deep nanohole arrays?up to 400 nm depth?provided outstanding sensing performance.Taking shallow Au nanoholes as masks,the underneath silicon was turned into deep silicon nanowell template,which was further deposited thick film of silver to form deep silver nanowell arrays.With the aim of better optical and sensing performance,we regulated a variety of structure parameters and finally screened out the best fabrication conditions,under which the structure's sensitivity achieved 933 nm/RIU.The optimized deep silver nanowell arrays were eventually used in antigen-antibody recognition immunoassay to prove their application prospect in actual biosensing.Colloidal lithography obtained shallow holes were deepened by RIE and employed as templates for the transformation of 2D metallic nanohole arrays to 3D deep metallic nanohole arrays.Exactly as we expected,the nanostrcture's sensitivity was much higher than most peer shallow metallic nanohole arrays,which will provide a new direction for the future 3D metallic interfaces applied in plasmonic sensing.In the 4^th chapter,we took advantage of the polymer's elasticity and proposed a fire-new method to build deep elliptical silver nanowell arrays.It was based on stretchable imprinting and polymer colloidal lithography.Compared with circular nanohole arrays,elliptical metallic nanohole arrays possess higher transmission and better sensitivity.However fabrication of large area aspect ratio highly tunable elliptical nanohole arrays is still a challenge.We found that utilizing colloidal lithography could attain orderly aligned silicon nanopillar arrays,which could be replicated to nanohole arrays negative mold.Benefit from the high elasticity of polydimethylsiloxane?PDMS?mold,the as-prepared deep elliptical silver nanowell arrays'aspect ratio can be highly tuned from 1.7 to 5.0.Based on the optimization of polarization direction and structural parameters including nanowell depth,aspect ratio,and hole size,the sensing performance of deep-elliptical-silver-nanowell arrays could finally be enhanced to 1414.1 nm/RIU.The optimized sample was proved the possibility as an immunoassay platform finally.The elastomer stretching and imprinting method realized the large range tunability of elliptical nanohole's aspect ratio.The deep elliptical Si nanowell template can be reused many times.The preparation approach of stretchable imprinting combining colloidal lithography will broaden the path for anisotropic metallic nanostructured surfaces.Meanwhile,elliptical metallic nanohole arrays'satisfying sensitivity also enables them predominant application in the future.