Heterostructured CoOx–TiO2 Mesoporous/Photonic Crystal Bilayer Films for Enhanced Visible-Light Harvesting and Photocatalysis

Heterostructured bilayer films, consisting of co-assembled TiO2 photonic crystals as the bottom layer and a highly performing mesoporous P25 titania as the top layer decorated with CoOx nanoclusters, are demonstrated as highly efficient visible-light photocatalysts. Broadband visible-light activation of the bilayer films was implemented by the surface modification of both titania layers with nanoscale clusters of Co oxides relying on the chemisorption of Co acetylacetonate complexes on TiO2, followed by post-calcination. Tuning the slow photon regions of the inverse opal supporting layer to the visible-light absorption of surface CoOx oxides resulted in significant amplification of salicylic-acid photodegradation under visible and ultraviolet (UV)–visible light (Vis), outperforming benchmark P25 films of higher titania loading. This enhancement was related to the spatially separated contributions of slow photon propagation in the inverse opal support layer assisted by Bragg reflection toward the CoOx-modified mesoporous P25 top layer. This effect indicates that photonic crystals may be highly effective as both photocatalytically active and backscattering layers in multilayer photocatalytic films.

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Protection against a wide UV wavelength range by Bragg reflection from polycrystalline colloidal photonic crystals

Journal of Materials Chemistry C ◽

10.1039/c9tc00680j ◽

2019 ◽

Vol 7 (25) ◽

pp. 7512-7515 ◽

Cited By ~ 1

Author(s):

Toshimitsu Kanai ◽

Shinoka Nakashima ◽

Tomomi Oki

Keyword(s):

Photonic Crystals ◽

Visible Light ◽

Ultraviolet Light ◽

Wavelength Range ◽

Incident Angle ◽

Bragg Reflection ◽

Colloidal Crystals ◽

Visible Light Region ◽

Colloidal Photonic Crystals ◽

Light Region

Polycrystalline colloidal crystals can block ultraviolet light of 290–400 nm, regardless of the incident angle, while maintaining transparency in the visible light region.

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Graphene Quantum Dot-TiO2 Photonic Crystal Films for Photocatalytic Applications

Nanomaterials ◽

10.3390/nano10122566 ◽

2020 ◽

Vol 10 (12) ◽

pp. 2566

Author(s):

Maria-Athina Apostolaki ◽

Alexia Toumazatou ◽

Maria Antoniadou ◽

Elias Sakellis ◽

Evangelia Xenogiannopoulou ◽

...

Keyword(s):

Photonic Crystal ◽

Visible Light ◽

Performance Enhancement ◽

Photonic Band Gap ◽

Light Trapping ◽

Stop Band ◽

Graphene Quantum Dots ◽

Inverse Opal ◽

Crystal Films ◽

Visible Light Activation

Photonic crystal structuring has emerged as an advanced method to enhance solar light harvesting by metal oxide photocatalysts along with rational compositional modifications of the materials’ properties. In this work, surface functionalization of TiO2 photonic crystals by blue luminescent graphene quantum dots (GQDs), n–π* band at ca. 350 nm, is demonstrated as a facile, environmental benign method to promote photocatalytic activity by the combination of slow photon-assisted light trapping with GQD-TiO2 interfacial electron transfer. TiO2 inverse opal films fabricated by the co-assembly of polymer colloidal spheres with a hydrolyzed titania precursor were post-modified by impregnation in aqueous GQDs suspension without any structural distortion. Photonic band gap engineering by varying the inverse opal macropore size resulted in selective performance enhancement for both salicylic acid photocatalytic degradation and photocurrent generation under UV–VIS and visible light, when red-edge slow photons overlapped with the composite’s absorption edge, whereas stop band reflection was attenuated by the strong UVA absorbance of the GQD-TiO2 photonic films. Photoelectrochemical and photoluminescence measurements indicated that the observed improvement, which surpassed similarly modified benchmark mesoporous P25 TiO2 films, was further assisted by GQDs electron acceptor action and visible light activation to a lesser extent, leading to highly efficient photocatalytic films.

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