Solar Photocatalytic Activity of Ba-Doped ZnO Nanoparticles: The Role of Surface Hydrophilicity.

Bare zinc oxide (ZnO) and Ba-doped ZnO (BZO) samples were prepared by using a simple precipitation method. The effects of Barium doping on the structural, morphological, and optoelectronic properties, as well as on the physico-chemical features of the surface were investigated and correlated with the observed photocatalytic activity under natural solar irradiation. The incorporation of Ba2+ ions into the ZnO structure increased the surface area by ca. 14 times and enhanced the hydrophilicity with respect to the bare sample, as demonstrated by infrared spectroscopy and contact angle measurements. The surface hydrophilicity was correlated with the enhanced defectivity of the doped sample, as indicated by X-ray diffraction, Raman, and fluorescence spectroscopies. The resulting higher affinity with water was, for the first time, invoked as an important factor justifying the superior photocatalytic performance of BZO compared to the undoped one, in addition to the slightly higher separation of the photoproduced pairs, an effect that has already been reported in literature. In particular, observed kinetic constants values of 8∙10-3 and 11.3∙10-3 min-1 were determined for the ZnO and BZO samples, respectively, by assuming first order kinetics. Importantly, Ba doping suppressed photocorrosion and increased the stability of the BZO sample under irradiation, making it a promising photocatalyst for the abatement of toxic species.

Enhanced Solar Light Photocatalytic Activity of Ag Doped TiO2-Ag3PO4 Composites.

Composites comprised of Ag3PO4 and bare TiO2 (TiO2@Ag3PO4) or silver doped TiO2 (Ag@TiO2-Ag3PO4) have been synthesized by coupling sol-gel and precipitation methods. For the sake of comparison, also the bare components have been similarly prepared. All the samples have been characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), Fourier transformed infrared spectroscopy (FTIR), photoelectrochemical measurements, and specific surface area (SSA) analysis. The optoelectronic and structural features of the samples have been related to their photocatalytic activity for the degradation of 4-nitrophenol under solar and UV light irradiation. Coupling Ag3PO4 with silver doped TiO2 mitigates photocorrosion of the Ag3PO4 counterpart, and remarkably improves the photocatalytic activity under solar light irradiation with respect to the components, to the TiO2-Ag3PO4 sample, and to the benchmark TiO2 Evonik P25. These features open the route to future applications of this material in the field of environmental remediation.

TiO2-PANI/Cork composite: A new floating photocatalyst for the treatment of organic pollutants under sunlight irradiation.

A novel photocatalyst based on TiO2-PANI composite supported on small pieces of cork has been reported. It was prepared by simple impregnation method of the polyaniline (PANI)-modified TiO2 on cork. The TiO2-PANI/Cork catalyst shows the unique feature of floating on the water surface. The as-synthesized catalyst was characterized by X-ray diffraction (XRD), scanning electron micrograph (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), UV-vis diffuse reflectance spectra (UV-vis DRS) and the Brunauer-Emmett-Teller (BET) surface area analysis. Characterization suggested the formation of anatase highly dispersed on the cork surface. The prepared floating photocatalyst showed high efficiency for the degradation of methyl orange dye and other organic pollutants under solar irradiation and constrained conditions, i.e., no-stirring and no-oxygenation. The TiO2-PANI/Cork floating photocatalyst can be reused for at least four consecutive times without significant decrease of the degradation efficiency.

Synthesis and crystal structure of 4-fluoro-benzyl-ammonium di-hydrogen phosphate, [FC6H4CH2NH3]H2PO4.

The asymmetric unit of the title salt, [p-FC6H4CH2NH3]+·H2PO4-, contains one 4-fluoro-benzyl-ammonium cation and one di-hydrogen phosphate anion. In the crystal, the H2PO4- anions are linked by O-H⋯O hydrogen bonds to build corrugated layers extending parallel to the ab plane. The FC6H4CH2NH3+ cations lie between these anionic layers to maximize the electrostatic inter-actions and are linked to the H2PO4- anions through N-H⋯O hydrogen bonds, forming a three-dimensional supra-molecular network. Two hydrogen atoms belonging to the di-hydrogen phosphate anion are statistically occupied due to disorder along the OH⋯HO direction.

Synthesis and crystal structure of 4-(2-ammonio-eth-yl)morpholin-4-ium di-chlorido-diiodido-cadmate/chlorido-tri-iodido-cadmate (0.90/0.10).

The crystal structure of the title compound, (C6H16N2O)[CdCl1.90I2.10], a new organic-inorganic hybrid salt synthesized in the form of single crystals, consists of discrete statistically distributed di-chlorido-diiodido-cadmate/chlorido-tri-iodido-cadmate anions (occupancy ratio 0.90:0.10) and 4-(2-ammonio-eth-yl)morpholin-4-ium cations, [NH3(CH2)2NH(CH2)4O]2+. The cations are linked by inter-molecular N-H⋯O hydrogen bonds, forming corrugated chains extending parallel to the c axis. The [CdCl1.90I2.10]2- tetra-halidocadmate anions lie between the chains to maximize the electrostatic inter-actions and are connected with the organic cations via N-H⋯Cl and C-H⋯Cl(I) hydrogen bonds developing in the ab plane and leading to the formation of a three-dimensional network structure. The tetra-coordinate CdII atom has a distorted tetra-hedral conformation, with a τ4 index of 0.87.

Crystal structure of non-centrosymmetric bis-(4-meth-oxy-benzyl-ammonium) tetra-chlorido-zincate.

The structure of the title non-centrosymmetric organic-inorganic hybrid salt, (C8H12NO)2[ZnCl4], consists of two 4-meth-oxy-benzyl-ammonium cations sandwiched between anionic layers, formed by isolated tetra-chlorido-zincate tetra-hedra. The double layers extend parallel to the ac plane. The crystal packing is assured by Coulombic inter-actions and by a complex N-H⋯Cl and C-H⋯Cl hydrogen-bonding system mostly involving the positively charged ammonium groups and the chloride ligands of the isolated tetra-hedral [ZnCl4](2-) units. One of the methyl-ene-ammonium groups is disordered over two sets of sites in a 0.48 (2):0.52 (2) ratio. The crystal investigated was twinned by non-merohedry with a twin component ratio of 0.738 (2):0.262 (2).