SPR Nanoarrays: Fabrication And Performance Study

In the realm of optical bio-sensing, surface plasmon resonance(SPR) is regarded as an advanced and commonly used technique for the analysis of bio-molecular interaction, owing to its great advantages, such as real-time detection, label-free, and small consumption of samples. For the conventional SPR biosensor, it requires prism and complicated optical system. Although it has good stability and high sensitivity, it fails to achieve miniaturization and integration and also has some limitation in detection of extremely low concentration of biomolecules. In 1998, Ebbesen et al. for the first time introduced the noble metal nanohole arrays. Such a structure has high transparency and its SPR effect is subject to the surface refraction. Based on these unique properties, this structure can be widely used in high-sensitivity biodetection. However, current approaches for the fabrication of patterned metal nano structure can not provide large area and periodic nanoarrays, restricting the industrial applications. Therefore, how to fabricate large-area, low-cost nanoarray structures and how to improve the sensitivity and selectivity in biodetection have been the major issues to consider.To address those problems, in this thesis we proposed several research objectives: to fabricate large-area, low-cost metal nanoarrays with various morphologies; to investigate and tune key factors, such as structure dimension, height, and bulk density; to detect specific biomolecules. In details, we utilize closely-packed polystyrene nanospheres, which is fabricated by emulsion polymerization, as a mask to perform metal deposition through the interstitial regions of the mask via a series of techniques, such as nanosphere lithography(NSL), magnetron sputtering(MS), reactive ion etching(RIE) and metal-assisted chemical etching(MACE). Metal nanoarrays with various morphologies are fabricated and further controllable synthesis can be fulfilled by tuning the length and diameter of nanoarrays. Various measurements including UV-Vis, TEM, SEM and so on are carried out to study optical performance. Based on the SPR effect of nanoarray structures, Raman test is performed in terms of R6 G. The main contents and conclusions are as follows:(1) Synthesis of PS nanometer microspheres and being used as templates to build various microstructures of metal nanoarrays structure: The synthesis of PS nanospheres and fabrication of metal nanoarrays based on PS-template: Monodispersed PS nanospheres with a diameter of 300 nm weresynthesized by emulsion polymerization method. PS films prepared by manual pulling and LB technique were studied. Subsequently, different nanoarray structures including gold-wrapped spheres, triangle dot arrays, and gold nanohole arrays were fabricated by using PS template and other processing techniques such as NSL, RIE and MP. The optical performance was studied, especially for the gold nanoarrays. By tuning the RIE and MS, we can control the thickness and diameter of nanoarrays. The results reveal that gold nanoarrays have an excellent SPR effect. The SPR peak would blue shift as the etching and sputtering time increase.(2) Gold assisted chemical etching method to construct silicon nanometer column array structure with enhanced effect of reducing reflection, and realize the fine adjustment of the length and diameter of the array: In this section, the prepared gold nanohole arrays were used as templates, to fabricate the Si nanopillar arrays associated with MACE. The diameter and height of Si nanopillar arrays could be controlled with the different RIE and chemical etching time. The research results showed that the diameter of the Si nanopillar arrays decrease as the RIE time increasing. Inversely, the height increased as the chemical etching time increasing. The controllable fabrication of the Si nanopillar arrays could be realized. More importantly, the Au/Si nanopillar arrays could be used in the many applications, such as solar cell and bio-detection, because of their obvious anti-reflective and plasmonic effects.(3) Nanoarray structures with SPR effect to test the rhodamine: choosing gold nanohole and Si nanopillar arrays with precisely controlable structure parameters as the research object, choosing rhodamine molecules as detecting target, a particular high sensitivity detection of biological molecules was carried out by surface enhanced Raman spectra. The results show that the both nanoarrays have the Raman enhancement effect to R6 G molecules. Among them, Raman enhancement effect of gold nanohole arrays is obvious. The minimum detectable concentration of R6 G can reach 10-12 M, and enhancement factor was in 108 orders of magnitude, greatly improving the detection sensitivity.