title: Structural Engineering of Nanoporous Anodic Alumina Photonic Crystals by Sawtooth-like Pulse Anodization.
abstract: This study presents a sawtooth-like pulse anodization approach aiming to create a new type of photonic crystal structure based on nanoporous anodic alumina. This nanofabrication approach enables the engineering of the effective medium of nanoporous anodic alumina in a sawtooth-like manner with precision. The manipulation of various anodization parameters such as anodization period, anodization amplitude, number of anodization pulses, ramp ratio and pore widening time allows a precise control and fine-tuning of the optical properties (i.e., characteristic transmission peaks and interferometric colors) exhibited by nanoporous anodic alumina photonic crystals (NAA-PCs). The effect of these anodization parameters on the photonic properties of NAA-PCs is systematically evaluated for the establishment of a fabrication methodology toward NAA-PCs with tunable optical properties. The effective medium of the resulting NAA-PCs is demonstrated to be optimal for the development of optical sensing platforms in combination with reflectometric interference spectroscopy (RIfS). This application is demonstrated by monitoring in real-time the formation of monolayers of thiol molecules (11-mercaptoundecanoic acid) on the surface of gold-coated NAA-PCs. The obtained results reveal that the adsorption mechanism between thiol molecules and gold-coated NAA-PCs follows a Langmuir isotherm model, indicating a monolayer sorption mechanism.
authors.affiliation: School of Chemical Engineering, The University of Adelaide , Engineering North Building, 5005 Adelaide, Australia.
authors.forename: Cheryl Suwen
authors.initials: CS
authors.lastname: Law
authors.affiliation: School of Chemical Engineering, The University of Adelaide , Engineering North Building, 5005 Adelaide, Australia.|Institute for Photonics and Advanced Sensing (IPAS), The University of Adelaide , 5005 Adelaide, Australia.|ARC Centre of Excellence for Nanoscale BioPhotonics (CNBP), The University of Adelaide , 5005 Adelaide, Australia.
authors.forename: Abel
authors.initials: A
authors.lastname: Santos
authors.affiliation: School of Chemical Engineering, The University of Adelaide , Engineering North Building, 5005 Adelaide, Australia.
authors.forename: Mahdieh
authors.initials: M
authors.lastname: Nemati
authors.affiliation: School of Chemical Engineering, The University of Adelaide , Engineering North Building, 5005 Adelaide, Australia.
authors.forename: Dusan
authors.initials: D
authors.lastname: Losic
keywords: nanoporous anodic alumina; photonic crystals; reflectometric interference spectroscopy; sawtooth-like pulse anodization; structural engineering