30 March 2009 Interference color of anodized aluminum oxide (AAO) films for sensor application
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Anodized aluminum oxide (AAO) membranes are fabricated under different anodization potentials in dilute sulfuric acid. Here we report the growth of AAO under 10, 15, 20, and 25V. These AAO membranes consist of nanopores with pore-to-pore distance from 35 to 69 nm. When AAO membranes are kept thin (less than ~500 nm), together with the unreacted aluminum substrate, interference colors are observed. The inference color of the membrane is changed by its thickness and the pore-to-pore distance, which is controlled by the anodization time and voltage, respectively. By using thin film interference model to analyze the UV-Vis reflectance spectra, we can extract the thickness of the membrane. Thus the linear growth of AAO membrane in sulfuric acid with time during the first 15 minutes is validated. Coating poly (styrene sulfonate) (PSS) sodium salt and poly (allylamine hydrochloride) (PAH) layer by layer over the surface of AAO membrane consistently shifts the interference colors. The red shift of the UV-Vis reflectance spectrum is correlated to the number of layers. This color change due to molecular attachment and increasing thickness is a promising method for chemical sensing.
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Yu Liu, Yu Liu, Ming L. Wang, Ming L. Wang, J. Ernesto Indacochea, J. Ernesto Indacochea, H. Hau Wang, H. Hau Wang, } "Interference color of anodized aluminum oxide (AAO) films for sensor application", Proc. SPIE 7292, Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2009, 729217 (30 March 2009); doi: 10.1117/12.814780; https://doi.org/10.1117/12.814780

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