Achieving Color and Function with Structure: Optical and Catalytic Support Properties of ZrO2 Inverse Opal Thin Films

Geoffrey I N Waterhouse; Wan-Ting Chen; Andrew Chan; Dongxiao Sun-Waterhouse

doi:10.1021/acsomega.8b01334

Achieving Color and Function with Structure: Optical and Catalytic Support Properties of ZrO₂ Inverse Opal Thin Films

ACS Omega. 2018 Aug 21;3(8):9658-9674. doi: 10.1021/acsomega.8b01334. eCollection 2018 Aug 31.

Authors

Geoffrey I N Waterhouse^{1

2

3}, Wan-Ting Chen^{1

2

3}, Andrew Chan^{1

2

3}, Dongxiao Sun-Waterhouse¹

Affiliations

¹ School of Chemical Sciences, The University of Auckland, Auckland 1010, New Zealand.
² The MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington 6140, New Zealand.
³ The Dodd-Walls Centre for Photonic and Quantum Technologies, Dunedin 9054, New Zealand.

Abstract

Taking inspiration from natural photonic crystal architectures, we report herein the successful fabrication of zirconia inverse opal (ZrO₂ IO) thin-film photonic crystals possessing striking iridescence at visible wavelengths. Poly(methyl methacrylate) (PMMA) colloidal crystal thin films (synthetic opals) were first deposited on glass microscope slides, after which the interstitial voids in the films were filled with a Zr(IV) sol. Controlled calcination of the resulting composite films yielded iridescent ZrO₂ IO thin films with pseudo photonic band gaps (PBGs) along the surface normal at visible wavelengths. The PBG position was dependent on the macropore diameter (D) in the inverse opals (and thus proportional to the diameter of the PMMA colloids in the sacrificial templates), the incident angle of light with respect to the surface normal (θ), and also the refractive index of the medium filling the macropores, all of which were accurately described by a modified Bragg's law expression. Au/ZrO₂ IO catalysts prepared using the ZrO₂ IO films demonstrated outstanding performance for the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH₄, which can be attributed to the interconnected macroporosity in the films, which afforded a high Au nanoparticle dispersion and also facile diffusion of 4-nitrophenol to the catalytically active Au sites.