Study On Block Copolymer-Templated Preparation And Optical Properties Of Silver Nanoarrays

As a kind of effective SERS substrates,silver nanoarrays have wide applications in molecular structure identification,chemical sensing and biological detection.Block copolymer-templated assembly has become one of the hottest research directions in the nanofabrication field due to its variations in nanopatterns and flexibility in fine structure control.In this work,block copolymer PS-b-P4VP was used as template to fabricate a series of SERS-active silver nanoarrays on silicon wafers by simple controllable displacement reactions.Silver-gold composite nanoarrays were also developed to improve the SERS activity.The nanoarrays,structures and their relative optical properties were investigated,and the potential applications in SERS dection were also explored.The main contents of this thesis are summarized as following:Firstly,we developed a simple approach to prepare uniform silver nanoarrays mimicking the block copolymer template.Large-area reproducible and size-controllable silver nanoarrays with high SERS activities were fabricated by reconstructing the block copolymer nanopatterns with ethanol treatment,which solved the problem of heterogeneous irregular silver deposition.The growth mechanism of silver nanoparticle arrays on both original and reconstructed patterns was comparatively discussed.Three kinds of SERS probes were employed to evaluate the SERS effects of as-obtained series silver nanoarrays in detail under the excitation wavelength of 532nm,785nm,respectively.The reproducibility of SERS singal intensity and detection limit was also investigated.The SERS enhancement factor(EF)of silver nanoarrays was calculated as 3.08×105.Then,silver-gold composite nanoarrays were fabricated by several schemes based on the firstly-developed silver nanoarrays in this work.The composite structures and relative Ag/Au ratio,SERS performances were investigated.Silver-gold composite nanoarrays with high uniformity and controllable ratio were successfully fabricated by using silver nanoarrays reacted with HAuCl4/HF solution,which induced a significantly increased intensity under 785nm excitation and kept similar SERS intensity under 532nm excitation.The SERS EF of silver-gold nanoarrays under 785nm excitation can be markedly increased by one order of magnitude,upto 1.1×106.Finally,the SERS applications of as-fabricated noble metal nanoarrays were explored.The feasibility of quantitative detection of nile blue A was proved,with R2 value of 0.97.Two kinds of SERS probes could be separately identified from their mixture solution by using silver nanoarrays as SERS substrate.A lable-free detection of adenosine,which considered as a cancer biomarker,could be achieved,with the detection limit of 10?M.This study provides a new way to rational design and controllable fabrication of noble metallic nanostructures with modulated optical properties.