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In the present work Cu 2 O shape tailored microcrystals were obtained and investigated. The used shape-tailoring approach was based upon the variation of the starting precursor (copper(II) acetate and copper(II) chloride, the latter one being also much more cheaper and easily accessible), the synthesis temperature (60, 70 and 80 °C, respectively) and the shape tailoring agent applied (PVP vs. EDTA). It was found that cubic and polyhedral monodisperse microcrystals were obtained, which showed enhance visible light photocatalytic activity in the degradation of methyl orange. The activity was dependent of the formation of metallic Cu (the formed metallic nanoparticles were obtained when PVP was used), the microcrystals' size and morphology. The band-gap values were directly linkable to the obtained photocatalytic activity, while in the first derivative DRS spectra the electron transition contribution of facet (111) was also found, alongside of the polycrystalline Cu 2 O electron transition contribution. Also, the surface hydrophylicity played a crucial role in the determination of the photocatalytic properties as evidenced by IR measurements and DLS investigations as well. Unlabelled Image • The nature of the precursor predetermined the Cu 2 O microparticles' morphology • Hydrophylicity was a key issue in the determination of the Cu 2 O's photoactivity • Shape-tailored Cu 2 O's (111) facet influenced the visible light absorption properties • EDTA stabilized efficiently Cu 2 O microparticles, inhibiting metallic Cu formation [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Proofs for the titanates photosensitization with the surface charge transfer Ti-complexes. • The surface CT complexes photosensitize titanates under Vis as well as UV light. • The visible-light induced photocatalytic activity of materials is as high as under UV. • High improvement of the photocurrents generation under UV light by the surface complexation. Abstract For the first time, photosensitization of selected alkaline titanates with surface charge transfer complexes has been proven. Activation of BaTiO 3 , SrTiO 3 and CaTiO 3 to visible as well as ultraviolet light has been achieved by impregnation with catechol, salicylic acid and 2,3-naphthalenediol. Simple modification of titanates with organic compounds forming inner-sphere CT complexes with Ti atoms located at the surface of semiconductors resulted in coloration of the materials. Even though acceptor electronic states of titanates are characterized by a higher energy compared with titania (even up to 0.75 eV higher for CaTiO 3), complexes formed at their surface absorb in similar or even broader optical range of visible light. Beside changes in the absorption properties, used modifications also strongly influenced their photoelectrochemical and photocatalytic properties. In contrast to similarly modified titanium dioxide, modified titanates show significantly improved photocatalytic activity not only under visible light but also within ultraviolet range of radiation. Remarkably increased efficiency of photocurrent generation within the UV range of radiation may suggest that apart from observed electron transfer from HOMO of the complex to conduction band (CB) of the semiconductor also an indirect photosensitization mechanism involving the electron transfer from the excited complexes to the CB of titanates may take place. [ABSTRACT FROM AUTHOR]

A series of CuC 2 O 4 /TiO 2 heterostructures with different mass ratio have been prepared via a simple precipitation method. Compared to bare P25 TiO 2 and pure CuC 2 O 4 , the as-prepared CuC 2 O 4 /TiO 2 exhibited superior activity and stability for the degradation of propylene under visible light. Results of X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectroscopy (DRS) indicated that there is an intimate interaction between CuC 2 O 4 and P25 TiO 2 nanoparticles by means of the coordination bond of O on the surface of TiO 2 with Cu atom in CuC 2 O 4 molecular. The strong activity of CuC 2 O 4 /TiO 2 heterostructure is due to the interfacial charge transfer (IFCT) from the valence band of the TiO 2 to the CuC 2 O 4 nanoparticles. In addition, compared to Cu (II)/TiO 2 synthesized using the same amount of CuSO 4 solution, CuC 2 O 4 /TiO 2 exhibited much higher visible light activity for the degradation of propylene because of higher atom ratio of Cu to Ti, more visible light absorption and stronger action between CuC 2 O 4 and TiO 2 . [ABSTRACT FROM AUTHOR]