Versatile fabrication of spherical inverse opals from diverse materials including Bi₂O₃/g-C₃N₄ and MXene/H-TiO₂ using hierarchical microspheres as templates

Abstract

Inverse opals with spherical morphologies, fabricated to accommodate a diverse range of material systems, are of significant importance for applications requiring particle-dispersed functional materials with photonic management capabilities. In this paper, hierarchical microspheres (HMs) with tier-1 diameters ranging from 5 μm to 250 μm, and silica or polystyrene as tier-2 microspheres of various diameters, are prepared using microfluidic methods and used as templates for spherical inverse opals. Hierarchical microsphere-based inverse opals (HMIOs), made from various individual materials such as Al₂O₃, TiO₂, ZnO, SiO₂, Bi₂O₃, and g-C₃N₄, as well as from composites like Bi₂O₃/g-C₃N₄ and Al₂O₃/TiO₂, are obtained using atomic layer deposition, sol-gel filling, and chemical vapor deposition methods. The wavelength of the reflection peaks induced by the photonic stop band is primarily determined by the periodicity of the pores, while the reflection peak intensity in HMIOs depends on the orderliness of the pores, which increases with their primary diameter. Among the materials, Bi₂O₃/g-C₃N₄ HMIOs exhibit the best photocatalytic degradation performance due to the matched energy levels. MXene-incorporated hydrogenated TiO₂ HMIOs, produced through microfluidic processing, also demonstrate an enhanced photocatalytic degradation rate, which is 1.74 times higher than that of the corresponding material without MXene.