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 ...

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Electrodeposited conducting polymer films derived from aromatic monomers are known to possess properties that depend significantly on the deposition protocol, particularly the electrochemical control function employed. This study explores the underlying reasons for this common observation for the specific case of polypyrrole films deposited from aqueous media onto gold electrodes under potentiostatic, potentiodynamic and galvanostatic control. Although the control functions impose different conditions, the control parameters (potential, potential range and scan rate, and current) were selected so as generate films at comparable rates; this avoids inappropriate attribution of structural and compositional variations to different thickness regimes, irrespective of how they were generated. In each case, film deposition was periodically interrupted and the film characterised by specular neutron reflectivity measurements. By using d 4pyrrole monomer in H 2 O solvent, the isotopic selectivity of neutron reflectivity was used to extract polymer and solvent concentration profiles as a function of distance from the electrode/film interface. Spatial integration of these profiles was used to quantify total film solvent populations; these are expressed as solvent volume fractions. Films grown under the three different control regimes have measurably distinct solvent volume fraction profiles and there is evolution of these profiles with increasing thickness. Ultimately, for the conditions employed, the order of increasing porosity (i.e. solvent content) by control function was potentiostatic < potentiodynamic < galvanostatic. At the end of the deposition process, the films were transferred to monomer-free electrolyte and redox cycled. This resulted in an overall increase in film solvation, but little difference in solvation with redox state (doping level). We conclude that film structure and associated solvation level do retain some memory of deposition protocol, but also respond to the medium of exposure.