Here, we use Andreev reflection spectroscopy to study the spin polarization of high quality CrO2 films. We study the spin polarization as a function of growth temperature, resulting in grain size and electrical resistivity. In these films low temperature growth appears to be a necessary but not sufficient condition to guarantee the observation of high spin polarization, and this is only observed in conjunction with suppressed superconducting gap values and anomalously low interface properties. We suggest that this combination of observations is a manifestation of the long range spin triplet proximity effect.

Boron carbide thin films were synthesised by laser-assisted chemical vapour deposition (LCVD), using a CO 2 laser beam and boron trichloride and methane as precursors. Boron and carbon contents were measured by electron probe microanalysis (EPMA). Microstructural analysis was carried out by Raman microspectroscopy and glancing incidence X-ray diffraction (GIXRD) was used to study the crystallographic structure and to determine the lattice parameters of the polycrystalline films. The rhombohedral-hexagonal boron carbide crystal lattice constants were plotted as a function of the carbon content, and the non-linear observed behaviour is interpreted on the basis of the complex structure of boron carbide.

This paper reports on a new and swift hydrothermal chemical route to prepare titanate nanostructures (TNS) avoiding the use of crystalline TiO 2 as starting material. The synthesis approach uses a commercial solution of TiCl 3 as titanium source to prepare an amorphous precursor, circumventing the use of hazardous chemical compounds. The influence of the reaction temperature and dwell autoclave time on the structure and morphology of the synthesised materials was studied. Homogeneous titanate nanotubes with a high length/diameter aspect ratio were synthesised at 160 ºC and 24 h. A band gap of 3.06±0.03 eV was determined for the TNS samples prepared in these experimental conditions. This value is red shifted by 0.14 eV compared to the band gap value usually reported for the TiO 2 anatase.Moreover, such samples show better adsorption capacity and photocatalytic performance on the dye rhodamine 6G (R6G) photodegradation process than TiO 2 nanoparticles. A 98% reduction of the R6G concentration was achieved after 45 minutes of irradiation of a 10 ppm dye aqueous solution and 1g L -1 of TNS catalyst.All reagents were of analytical grade (Aldrich and Fluka) and were used as received. The solutions were prepared with Millipore Milli-Q ultra pure water. Materials TNS precursor synthesisThe TNS precursor was prepared using a procedure reported previously [20]. A titanium trichloride solution (10 wt.% in 20-30 wt.% HCl) diluted in a ratio of 1:2 in standard HCl solution (37 %) was used as titanium source. To this solution a 4 M ammonia aqueous solution was added dropwise under vigorous stirring until complete precipitation of a white

This work reports on the synthesis of chromium (III, IV) oxides films by KrF laser-assisted CVD. Films were deposited onto sapphire substrates at room temperature by the photodissociation of Cr(CO)(6) in dynamic atmospheres containing oxygen and argon. A study of the processing parameters has shown that partial pressure ratio Of O-2 to Cr(CO)(6) and laser fluence are the prominent parameters that have to be accurately controlled in order to co-deposit both the crystalline oxide phases. Films consistent with such a two-phase system were synthesised for a laser fluence of 75 mJ cm(-2) and a partial pressure ratio of about 1. (c)

Here we report on a novel chemical route to synthesize homogenous cobalt doped titanate nanotubes (CoTNT), using an amorphous Co-doped precursor. The influence of the synthesis temperature, autoclave dwell time and metal doping on the structural and microstructural as well as on the optical properties of the synthesized titanate nanotubes is studied and discussed. The optical band gaps of the CoTNT samples are red shifted in comparison with the values determined for the undoped samples, such red shifts bringing the absorption edge of the CoTNT samples into the visible region. CoTNT materials also demonstrate particular high adsorption ability for methylene blue, the amount of the adsorbed dye being higher than the one predictable for a monolayer formation. This suggests the possibility of intercalation of the dye molecule between the TiO 6 layers of the TNT structure. It is also shown that the methylene blue sensitized Co-doped nanostructures are highly stable under UV radiation and present a strong and broad absorption in the visible region. O or even the lepidocrocite-type titanates with compositions Na x Ti 2-x/4 x/4 O 4 or H x Ti 2-x/4 x/4 O 4, where stands for vacancy [4][5][6][7][8].The TNTs' ion-exchange ability makes them potential materials for effective photocatalysts and solar energy cells applications [9][10][11]. However, they present a critical drawback: their high charge recombination rate and wide band gap (ca. 3.3 eV) limit the electron and hole photo-generation under visible irradiation. Therefore, the synthesis of TNT-based materials with either a broader range of light absorption and/or a lower charge recombination rate would be an important achievement toward the development of successful photoactive materials. Several works have been published on this issue including metal doping [12,13], co-sensitized with semiconductor nanoparticles and porphyrin zinc co-sensitization [14] or phthalocyanin-sensitization [15]. of 31This work reports on a swift chemical route to synthesize homogenous cobalt doped titanate nanotubes (CoTNTs), extending the hydrothermal process used to prepare undoped TNTs previously reported by our group [9]. It is shown that Co doping stabilizes the morphology of the TNTs in a synthesis temperature range of 160 ºC to 200 ºC, and brings TNTs' absorption edge to the visible region. The adsorption ability of the synthesized materials for methylene blue (MB) is studied and it is shown that not only the MB-sensitized CoTNT materials are highly stable under UV irradiation but also they present a strong and broad absorption in the visible region of the electromagnetic spectrum. Materials and MethodsAll reagents were of analytical grade (Aldrich and Fluka) and were used as received. The solutions were prepared with Millipore Milli-Q ultra-pure water. Materials TNTs precursor synthesisThe TNT precursor was prepared using a procedure previously reported by our group [16].The used titanium source was a titanium trichloride solution (10 wt.% in 20-30 wt.% HCl) diluted in a ratio of 1:2 ...

Titanate nanotubes (TNT) with different sodium contents have been synthesised using a hydrothermal approach and a swift and highly controllable post-washing processes. The influence of the sodium/proton replacement on the structural and morphological characteristics of the prepared materials was analysed. Different optical behaviour was observed depending on the Na + /H + samples' content. A band gap energy of 3.27±0.03 eV was estimated for the material with higher sodium content while a value of 2.81±0.02 eV was inferred for the most protonated material, which therefore exhibits an absorption edge in the near visible region. The point of zero charge of the materials was determined and the influence of the sodium content on the adsorption of both cationic and anionic organic dyes was studied. The photocatalytic performance of the TNT samples was evaluated in the rhodamine 6G degradation process. Best photodegradation results were obtained when using the most protonated material as catalyst, although this material has shown the lowest R6G adsorption capability.

A swift chemical route to synthesize Co-doped SnO 2 nanopowders is described. Pure andcrystalline nanoparticles were synthesized, with mean grain sizes < 5 nm and the dopant element homogeneously distributed in substitutional sites of the SnO 2 matrix. The UV-visible diffuse reflectance spectra of the Sn 1-x Co x O 2- samples reveal red shifts, the optical bandgap energies decreasing with increasing Co concentration. The samples' Urbach energies were calculated and correlated with their bandgap energies. The photocatalytic activity of the Sn 1-x Co x O 2- samples was investigated for the 4-hydroxylbenzoic acid (4-HBA) degradation process. A complete photodegradation of a 10 ppm 4-HBA solution was achieved using 0.02% (w/w) of Sn 0.95 Co 0.05 O 2- nanoparticles in 60 min of irradiation.

This letter reports on the magnetic properties of Ti1-xCoxO2 anatase phase nanopowders with different Co contents. It is shown that oxygen vacancies play a fundamental role in promoting the long-range ferromagnetic order in the material studied, in addition to the transition-metal doping. Furthermore, the results allow ruling out the premise of a strict connection between Co clustering and the ferromagnetism observed in the Co:TiO2 anatase system.Comment: 13 pages, 5 figure