Abstract
Carbon nanospheres were used as templates for the first time to prepare titania inverse opal photonic crystal. From the spheres, opal colloid crystals were made by vertical deposition on microscope slides, and TiO2 was grown on them using atomic layer deposition (ALD). For this technique, the relatively high thermal stability and the presence of oxygen containing functional groups on the surface of the carbon spheres are beneficial. Subsequent annealing burned out the template spheres, leaving behind the inverse opal structures. The upper solid TiO2 layer was removed with argon ion sputtering. The samples were characterized with SEM, Raman spectroscopy, XRD, EDX, UV–Vis diffuse reflectance spectroscopy and their photocatalytic activity was investigated in decomposing organic dyes under UV and visible illumination. A new approach was used to test photocatalysis on the surface by utilizing UV–Vis reflectance and Raman spectroscopy in conjunction.
Highlights
Photonic crystals, the inverse opal variants are in the center of many researches because of their favorable and tunable optical properties, which prevent the propagation of light in certain directions with specified frequencies [1,2]
The higher temperature tolerance and surface functional groups of the carbon spheres make them more suitable templates for atomic layer deposition than polymer spheres and are easier to remove than silica spheres
Facecentered cubic colloid crystals were prepared from the templates by taking advantage of colloidal self-assembly, and atomic layer deposition was utilized to fill the gaps between the spheres with titania
Summary
The inverse opal variants are in the center of many researches because of their favorable and tunable optical properties, which prevent the propagation of light in certain directions with specified frequencies [1,2] They can be made from a wide variety of dielectric materials, e.g. silicon, silica, titania, ZnO or CdSe, with methods such as sol-gel technique, atomic layer deposition (ALD) or electrodeposition [3,4,5,6,7,8]. Inverse opals can be prepared by top-down methods, but bottom-up techniques are more convenient, as they take advantage of the colloidal self-assembly [22,23,24] In these approaches, a colloid crystal is prepared from the template spheres, among which the most widely used are polystyrene, poly(methyl methacrylate) and silica, the gaps between the spheres are filled with the chosen dielectric material. The polymers can be burned out, and silica is usually removed by dissolving it with hydrogen fluoride [29,30,31]
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