Photocatalytic metamaterials: TiO2 inverse opals

Dipartimento di Chimica Analitica, Università di Torino, Via P: Giuria, 5, 10125 Torino, Italy.
Chemical Communications (Impact Factor: 6.83). 06/2011; 47(21):6147-9. DOI: 10.1039/c1cc11243k
Source: PubMed


The study of the photocatalytic activity of TiO(2) inverse opals showed that these structures behave as metamaterials: their properties arise principally from the 3D periodic structure of the material and marginally from porosity, reflectivity and scattering.

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    • "To clarify the relative importance of slow light, light scattering and improved mass transfer due to the porosity Sordello et al. performed the photocatalytic degradation of phenol at two different wavelengths on TiO 2 inverse opal and TiO 2 disordered macroporous powders (Sordello et al. 2011a). The wavelengths used were 365 nm, where, for the TiO 2 inverse opal employed, the slow photon effect was maximized, and 254 nm, where, on the contrary, the slow light was negligible. "

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    ABSTRACT: TiO2-based nanomaterials play currently a major role in the development of novel photochemical systems and devices. One of the key parameters determining the photoactivity of TiO2-based materials is the position of the band edges. Although its knowledge is an important prerequisite for understanding and optimizing the performance of photochemical systems, it has been often rather neglected in recent research, particularly in the field of heterogeneous photocatalysis. This paper provides a concise account of main methods for the determination of the position of the band edges, particularly those suitable for measurements on nanostructured materials. In the first part, a survey of key photophysical and photochemical concepts necessary for understanding the energetics at the semiconductor/solution interface is provided. This is followed by a detailed discussion of several electrochemical, photoelectrochemical, and spectroelectrochemical methods that can be applied for the determination of band edge positions in compact and nanocrystalline thin films, as well as in nanocrystalline powders.
    Full-text · Article · Jan 2011 · Advances in Physical Chemistry
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    ABSTRACT: The optical and photoelectrochemical behaviour of TiO2 inverse opals and TiO2 disordered macroporous structures has been investigated by means of UV-vis spectroscopy, cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy. These techniques, together with photonic band structure calculations, confirmed the better absorption of light of TiO2 inverse opals, due to the slow light phenomenon, and indeed the status of metamaterials for such structures. TiO2 inverse opals and TiO2 disordered macroporous structures are shown to have the same recombination rate of photogenerated charge carriers, but TiO2 inverse opals are characterized by a better reactivity towards O2 which can also contribute to the improvement of the photocatalytic activity observed by several groups.
    No preview · Article · Nov 2011 · Journal of Materials Chemistry
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