Detection of Cyclic Volatile Organic Compounds Using Single-Step Anodized Nanoporous Alumina Sensors

Conventional methods of fabricating anodic aluminum oxide (AAO) materials have utilized a multistep anodization process to manufacture sensor substrates and templates for nanostructured materials. The multistep anodization produces structured, highly ordered hexagonal nanopores. In this paper, it is demonstrated that a single-step anodization process employed in the manufacturing of moisture sensors produces a nanoporous AAO material suitable for the detection and discrimination of low molecular weight volatile organic compounds. Electrical impedance methods have been employed to analyze the electrical response of the single-step anodized AAO materials in the presence of cyclic organic vapors. The sensor exhibits an impedance response that discriminates cyclohexane, cyclohexene, benzene, toluene, and the three isomers of xylene. The impedance measurements have a direct correlation with the relative permittivity, polarizability, and dipole moments of the organic analytes.