Rational Management of Photons for Enhanced Photocatalysis in Structurally-Colored Nanoporous Anodic Alumina Photonic Crystals

Abstract

A comprehensive study on the engineering of titanium dioxide-functionalized nanoporous anodic alumina distributed Bragg reflectors (TiO 2-NAA-DBRs) for photocatalysis enhanced by the "slow photon" effect is presented. The photocatalytic performance of these composite photonic crystals (PCs) is assessed by monitoring photodegradation of a variety of organic molecules with absorbance bands across the spectral regions. This study demonstrates that photocatalytic performance of TiO 2-NAA-DBRs is enhanced by the "slow photon" effect when the edges of the PC's photonic stopband (PSB) fall within the absorbance band of the organic molecules. The photocatalytic performance is significantly enhanced when the PSB's red edge is in close proximity to the absorbance band of the organic molecules. Overall photocatalytic degradation is also dependent on the total pore length of the PC structure, charge of the organic molecules, percentage of vis-NIR irradiation and matrix complexity (i.e. interfering ions and molecules) when the PC's PSB is partially or entirely misaligned with respect to the absorbance band of the organic molecules. Finally, the real-life application of TiO 2-NAA-DBRs to degrade pollutants such as pesticides in environmental matrices is

Realization of high-quality optical nanoporous gradient-index filters by optimal combination of anodization conditions

“…Of all NAA-PCs structures, NAA-GIFs produced by sinusoidal pulse anodization feature a characteristically well-resolved, intense, narrow PSB associated with a smooth and periodic modulation of effective refractive index in depth, which is ~/4 narrower than that of their quarter-wave NAA-DBR analogues. 39 Well-resolved and narrow PSBs are desirable for different lightbased applications requiring a precise control over electromagnetic waves such as optical sensing and biosensing 11,12 , optical encoding 40,41 , lasing 42, 43 , light filtering 44,45 and photocatalysis [46][47][48] . Recent developments in pulse anodization technology have aimed at improving light control quality of NAA-PCs.…”

Integrating surface plasmon resonance and slow photon effects in nanoporous anodic alumina photonic crystals for photocatalysis

“…Semiconductor photocatalysts harvest the energy of incoming photons to drive chemical reactions for solar-to-fuel conversion and environmental remediation, including hydrogen (H 2 ) energy generation, [1][2][3] water treatment, [4][5][6][7][8][9][10][11] air purification, 12,13 ammonia (NH 3 ) synthesis, 14,15 carbon dioxide (CO 2 ) reduction 16,17 and warfare agents destruction. 18,19 In land-mark studies, Fujishima 20 and Carey 21 reported production of clean H 2 energy and degradation of organic pollutants by semiconducting titanium dioxide (TiO 2 ) under UV light irradiation, respectively.…”

“…We have recently demonstrated that TiO 2 -functionalized nanoporous anodic alumina photonic crystals (NAA-PCs), with rationally engineered optical properties, provide superior performance than that of conventional photocatalyst platforms in the photodegradation of a variety of organic pollutants. 10,11 NAA is an ideal platform to develop PC structures due to its highly controllable and versatile nanoporous structure composed of cylindrical nanopores. The optical features of the characteristic PSB in NAA-PCs can be modulated with precision by engineering their nanoporous structure in the form of different PC architectures, including distributed Bragg reflectors (DBRs), 11,47 bandpass filters, 48,49 Fabry-Pérot interferometers, 50,51 gradient-index filters, 10,[52][53][54] hybrid photonic crystals, 55 and optical microcavities.…”

Recent Advances in Opal/Inverted Opal Photonic Crystal Photocatalysts

“…[ 37–42 ] In particular, recent advances in the self‐assembly of nanoscopic building blocks have enabled fabrication of hierarchically ordered macro/mesoporous photocatalysts with tunable inter‐ and intraparticle porosity. [ 43–48 ] These nanostructures feature an interconnected network, which significantly improves the photocatalytic activity by enhancing molecular diffusion kinetics and increases the accessible surface area and the amount of adsorption and reactive sites. [ 49–56 ]…”