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A novel immobilized Ca 0.6 Ho 0.4 MnO 3 photocatalyst has been developed with high photocatalytic activity for Rhodamine 6G (Rh6G) photodegradation under visible light irradiation. The nanocrystalline Ca 0.6 Ho 0.4 MnO 3 films were successfully deposited by RFmagnetron sputtering on unheated quartz glass substrates using Ca 0.6 Ho 0.4 MnO 3 powder as sputtering target and its photocatalytic functionalities have been explored. The visible-lightresponsive photocatalytic activity of Ca 0.6 Ho 0.4 MnO 3 films was evaluated by the photodegradation of Rh6G aqueous solutions under visible light irradiation. The reusability of Ca 0.6 Ho 0.4 MnO 3 films on fresh dye samples was studied, showing an efficient reuse, without decreasing the photocatalytic decolorization efficiency. Furthermore, X-ray diffraction of the reused films did not reveal additional phases indicating high photochemical stability of the films even after reusing them in successive runs. The photocatalytic efficiency of the nanocrystalline Ca 0.6 Ho 0.4 MnO 3 films was further compared with TiO 2 films also produced by sputtering and the results revealed a significant improvement in photocatalytic activity over TiO 2 under visible light irradiation. Almost complete photodecolorization of a 5 ppm Rh6G solution was achieved in 4 h, while only 64% of dye degradation was observed in TiO 2 photoassisted process. This work provides a feasible route to fabricate high-performance immobilized ABO 3 -based nanomaterials, and the finding opens up a new venue for designing visible light sensitive ternary compounds for photocatalytical applications.

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With the aim of producing materials with enhanced optical and photocatalytic properties, titanate nanotubes (TNTs) modified by cobalt doping (Co-TNT) and by Na(+)→ Co ion-exchange (TNT/Co) were successfully prepared by a hydrothermal method. The influence of the doping level and of the cobalt position in the TNT crystalline structure was studied. Although no perceptible influence of the cobalt ion position on the morphology of the prepared titanate nanotubes was observed, the optical behaviour of the cobalt modified samples is clearly dependent on the cobalt ions either substituting the Ti(4+) ions in the TiO6 octahedra building blocks of the TNT structure (doped samples) or replacing the Na(+) ions between the TiO6 interlayers (ion-exchange samples). The catalytic ability of these materials on pollutant photodegradation was investigated. First, the evaluation of hydroxyl radical formation using the terephthalic acid as a probe was performed. Afterwards, phenol, naphthol yellow S and brilliant green were used as model pollutants. Anticipating real world situations, photocatalytic experiments were performed using solutions combining these pollutants. The results show that the Co modified TNT materials (Co-TNT and TNT/Co) are good catalysts, the photocatalytic performance being dependent on the Co/Ti ratio and on the structural metal location. The Co(1%)-TNT doped sample was the best photocatalyst for all the degradation processes studied.

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CaMn3O6 films with hierarchical nanostructures were deposited for the first time on unheated quartz glass substrates by the radio frequency (RF) magnetron sputtering technique using a polycrystalline CaMnO3 sample as sputtering target, and their photocatalytic activity was evaluated on the decolorization of Rhodamine 6G (Rh6G) aqueous solutions. The films scanning electron microscope (SEM) images evidence a growth of nanorods (NRs) arrays with planar endings and a narrow size distribution centered at about 30 nm in diameter. The CaMn3O6 films surface is uniform and presents a high density of nanorods (116 nanorods per μm2). The high surface area combined with the tunnels crystallographic structure, evidenced by X-ray diffraction (XRD), results in an effective photocatalyst for Rh6G degradation under visible light irradiation. Based on the photodegradation experiments, it is suggested that a process of dye self-sensitization can be one of the key factors of the superior photocatalytic performance of CaMn3O6 NRs. The kinetics of photocatalytic degradation of Rh6G follows a first-order reaction. Furthermore, XRD of the used films did not reveal additional phases indicating high photochemical stability, and the diffuse reflection infrared Fourier transform spectrum (DRIFT) does not show adsorbed organic species on the CaMn3O6 NRs surface. This work provides a potential route to develop high-performance immobilized nanostructures, and the achievements open up many possibilities to tailor visible light active materials for environmental applications.

Novel titanate nanotubes sensitized with ethylenediamine demonstrated promising photocatalytic performances for the degradation of psychoactive substances, caffeine and theophylline, and phenol removal.