| Porous anodic aluminum oxide (AAO) has been used as an important hardtemplate in nanofabrication, chemical/biological sensing, surface-enhancedspectroscopy, photovoltaics, photocatalysis, due to its controllable three-dimensionalstructural parameters and ordered nanostructures. The structural parameters of AAOdepend on the electrochemical parameters applied in the anodization process,because of which we can tune the structure in a sophisticated way by modifying theelectrochemical conditions, such as voltage applied, species and concentration ofelectrolyte solution, and post-processing, which is wet-etching by phosphoric acidsolution. However, natural self-ordering of AAO nanochannels only happens in astrict and narrow regime of anodization condition, limiting the possibilities ofnanostructures that can be fabricated using AAO as templates. Pre-texturing orpre-patterning has been proved to be a useful method in guiding the ordered AAOnanochannels growth in a pore distance that jumps out of the self-ordering regime.In our previous reports, we demonstrate that by combining nanosphere lithographyand subsequent metal deposition, we can build periodic ordered nanowell array onAl surface, which can guide hierarchical structural AAO template. Therefore, using NSL and metal deposition we can build ordered AAO template that is out theself-ordering regime. The detailed research content of this thesis include followingthree aspects:(1) Based on NSL and metal depositionpre-patterning method, we realized thefabrication of a hierarchical ultrathin AAO template and its through-hole process.Then the through-hole AAO template is used as a stencil mask for the fabrication ofunique nanodot arrays. The prepared nanodot arrays have a unique periodicity andspectral features that a conventional AAO template cannot possibly provide,.Transmission and angle-resolved spectra are used in comparing the LSPR propertyand optical property of the two kinds of nanodot arrays. The method we used tofabricate nanodot arrays break the stereotype that only hexagonal nanodot array witha fixed inter-pore distance can be made by AAO template, and the unique nanodotarrays has possible applications in plasmonics, photovoltaics, and photocatalysis.(2) Based on our previous method of pre-patterning the surface of Al, weexplore the fabrication of long-range ordered AAO template. In our previous method,the anodization voltage applied in the anodization of a hierarchical AAO template ishalf that of the empirical voltage. In this chapter, we use voltage that matches theperiod of the pre-patterns. The prepared AAO template has a period and inter-poredistance that is our of the self-ordering regime and has good growth sustainability.Our study can be an inspiration for further engineering the inter-pore distance andperiod of AAO template.(3)Self-ordering AAO template that has a typical inter-pore distance of100nmis used in the fabrication of a silver nanodot array, and then the silver nanodot arrayis used as a substrate for surface-enhanced Raman scattering (SERS). Theenhancement substrate is then embedded into a microfluidic chip, after beingcombined with our previously developed microfluidic Raman analyzer, we are able to build a microfluidic SERS platform. We optimize the pore-widening time toacquire a nanodot array structure with best enhancement performance. Themicrofluidic SERS platform we build has the advantage of portability from themicro-Raman analyzer and the high sensitivity from the silver nanodot array, and inthe meantime, we demonstrate that the platform can minimize the signal floodingfrom the PDMS cover for microfluidic channels. We realized low-concentrationmixture of two kinds of molecules, proving that the microfluidic SERS platform haspotential commercial values. |
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