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Abstract: Herein, we report the formation of TiO2/LDH self-assembled nanocomposite systems using the memory effect property of the layered clay-type materials. Two different synthesis approaches, based on the modification of the initial brucite-like sheets composition, were used in order to investigate the influence of the Ti4+ location on the quality of the final products: the reconstruction of a calcined MgAl-LDH in a TiOSO4·xH2O aqueous solution and the reconstruction of a calcined MgAlTi-LDH in aqueous solution. The reconstruction process, monitored using X-ray diffraction, IR spectroscopy, UV–vis diffuse reflectance spectroscopy, SEM and thermal analysis, produced different structural changes strongly related with the brucite-like sheets composition. The photocatalytic activity of the obtained nanocomposite systems was evaluated for the degradation of the methyl-orange (MO) dye. An intimate contact has been created between the anatase and the brucite-like sheets in the nanocomposite systems, which had a direct influence on the HO radical production enhancing thus the photocatalytic performances. When comparing the as-synthesized catalysts, the MgAlTi-LDH solid manifests very powerful photocatalytic effect due to the segregation of small, well defined TiO2 nanoparticles on the highly hydroxilated layered surface. Up to 93% of the dye could be removed by a TiO2/LDH-type nanocomposite system. Controlled thermal treatment of photocatalytic systems allowed us to tailor the quality of the photocatalytic active sites deposited on the layered support. The use of the TiO2/LDHs nanocomposites showed multiple advantages highlighted by the increased activity per mass, higher efficiencies at a decreased solid/liquid ratio, decreased reaction times, reduced agglomeration and easy to separate at the end of the processes. [Copyright &y& Elsevier]

Highlights: [•] Self-assemblies of CeO2 nanoparticles on ZnTi-LDHs or Zn2TiO4 systems are obtained. [•] The composition of the brucite-type layer influences the catalyst performances. [•] Good dispersion of the metal cations within the layers. [ABSTRACT FROM AUTHOR]

Abstract: Sn4+-containing LDH was prepared using the co-precipitation method at constant pH, and characterized using X-ray diffraction, UV–vis diffuse reflectance spectroscopy and TG/DTG methods. The obtained product was further exposed to different thermal treatments in order to obtain nano-sized coupled ZnO/SnO2 systems with enhanced photocatalytic performances than the ones obtained by mixing the two semiconductor oxides. The formation of a well-defined ZnO/SnO2 system and the crystallite size, fully investigated using XRD, micro-Raman scattering and UV–vis DR techniques, were found to be influenced by the nature of the precursors and the calcination temperature. The photocatalytic activity of the ZnO/SnO2 systems, evaluated for the photodegradation of methyl orange (MO) dye, was studied as a function of the initial pH, catalyst loading and the calcination temperature. The metal dispersion supplied by layered structures proved to be an advantage when preparing coupled ZnO/SnO2 systems, the photocatalytic activity being ∼2.3 times higher comparing with the physical mixtures performances. The maximum photocatalytic activity of the coupled ZnO/SnO2 system having a layered precursor was observed when using neutral pH, at a catalyst loading of 1g/L calcined at 600°C for 4h. [Copyright &y& Elsevier]

Abstract: Combined TiO2/SiO2 mesoporous materials were prepared by deposition of TiO2 nanoparticles synthesised via the acid-catalysed sol–gel method. In the first synthesis step a titania solution is prepared, by dissolving titaniumtetraisopropoxide in nitric acid. The influences of the initial titaniumtetraisopropoxide concentration and the temperature of dissolving on the final structural properties were investigated. In the second step of the synthesis, the titania nanoparticles were deposited on a silica support. Here, the influence of the temperature during deposition was studied. The depositions were carried out on two different mesoporous silica supports, SBA-15 and MCF, leading to substantial differences in the catalytic and structural properties. The samples were analysed with N2-sorption, X-ray diffraction (XRD), electron probe microanalysis (EPMA) and transmission electron microscopy (TEM) to obtain structural information, determining the amount of titania, the crystal phase and the location of the titania particles on the mesoporous material (inside or outside the mesoporous channels). The structural differences of the support strongly determine the location of the nanoparticles and the subsequent photocatalytic activity towards the degradation of rhodamine 6G in aqueous solution under UV irradiation. [Copyright &y& Elsevier]