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

Abstract

Taking inspiration from natural photonic crystal architectures, we report herein the successful fabrication of zirconia inverse opal (ZrO 2 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 ZrO 2 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/ZrO 2 IO catalysts prepared using the ZrO 2 IO films demonstrated outstanding performance for the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH 4 , 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.

Filling in the gaps: The nature of light transmission through solvent-filled inverse opal photonic crystals

“…Currently, there are several methods used in a wide variety of literature to approximate the effective refractive index of composite material [69,70]. Two common models applied to inverse opal materials to determine 𝑛 eff include the Drude [16,48,52,[71][72][73] and Parallel [58][59][60][61][62] models. The Drude model for inverse opal systems can be formalized as:…”

“…We present a detailed investigation into the nature of the PBG and angle-resolved structural color of TiO2 and SnO2 inverse opal structures, focusing on their spectral behavior in air, but also when infilled with a range of solvents. Only a surprisingly small number of publications [51,[58][59][60][61][62] have addressed the interesting optical properties of inverse opal materials in solvent media, including the nature of PBG bandwidth, directionality, and sensitivity of the degree of infilling. We present a full study on the effects of solvent infiltration in inverse opal materials and, to our knowledge, the first study to systematically investigate the effects of solvent infilling with variable incident angle that is fully consistent with the actual IO structure.…”

Hydrogel-Based Colloidal Photonic Crystal Devices for Glucose Sensing

“…Fortunately, they can still be used as templates to create new structures, and complete band gaps (stop-bands) might be achieved. The inverted opaline (inverse opal (IO)) structures can be directly replicated from opal-derived materials by utilizing inorganic materials, such as SiO 2 , SiC, ZrO 2 , and TiO 2 [26][27][28], or polymers such as polyurethane (PU) [29], which have attracted considerable interest in recent years owing to their novel optical and electronic properties; high specific surface areas; and potential applications in the realms of PBG materials, power sources, and catalysts.…”

Hierarchical Silica Inverse Opals as a Catalyst Support for Asymmetric Molecular Heterogeneous Catalysis with Chiral Rh‐diene Complexes

“…[1,2] In addition, IOs of oxides like SiO 2 , ZnO, Al 2 O 3 and ZrO 2 can be used as mesoporous supports for the immobilization of catalytically active metal nanoparticles (NPs) and coordination complexes. [3][4][5][6][7][8][9] However, controlling the size and dispersion of NPs embedded within such porous structures has proved to be difficult. [10] The majority of studies on catalytic applications of IOs are focused on photo-and electrocatalysis, e. g. photocatalytic reduction of CO 2 , [11] oxidation of CO, [12] degradation of organic materials for waste water treatment, [13][14][15][16] hydrogen production, [17] oxygen reduction, [18] and epoxidation of styrene.…”