Please cite this article as: E. Albiter, M.A. Valenzuela, S. Alfaro, G. Valverde-Aguilar, F.M. Martínez-Pallares, Photocatalytic deposition of Ag nanoparticles on TiO 2 : metal precursor effect on the structural and photoactivity properties, Journal of Saudi Chemical Society (2015), doi: http://dx.Abstract A series of 1 wt. % Ag-TiO 2 photocatalysts were obtained by photodeposition using different organic (acetylacetonate, Ag-A) and inorganic (nitrate, Ag-N, and perchlorate, Ag-C) silver precursors in order to determinate the influence of the silver precursor on the final properties of the photocatalysts. The resulting photocatalytic materials were characterized by different techniques (UV-Vis DRS, TEM/HRTEM and XPS) and their photocatalytic activity was evaluated in the degradation of rhodamine B (used as model pollutant) in aqueous solution under simulated solar light. The photocatalytic reduction of Ag species to Ag 0 on TiO 2 was higher with silver nitrate as precursor compared to acetylacetonate or perchlorate. All the Ag-modified TiO 2 photocatalysts exhibited a surface plasmon resonance effect in the visible region (400-530 nm) indicating different metal particle size depending on the Ag precursor used in their synthesis. A higher photocatalytic activity was obtained with all the Ag/TiO 2 samples compared with nonmodified TiO 2 . The descending order of photocatalytic activity was as follows: Ag-A/TiO 2 ≈ Ag-N/TiO 2 > Ag-C/TiO 2 > TiO 2 -P25. The enhanced photoactivity was attributed to the presence of different amounts Ag 0 nanoparticles homogeneously distributed on Ag 2 O and TiO 2 , trapping the photogenerated electrons and avoiding charge recombination.

The photosensitized oxidation of 9,10-dimethylanthracene with singlet oxygen in acetonitrile was investigated using a safranin O/silica composite as an heterogeneous delivery system of the photosensitizer. The only detected product was the corresponding endoperoxide (9,10-endoperoxianthracene) and its formation rate depended on the initial concentration of DMA, the light intensity and the amount of the composite. The kinetics of this reaction was compared with that of the reported kinetic model of photosensitized oxidations of organic compounds in homogeneous reactions. It was found that both reactions followed the same model, suggesting that the actual reaction between photoproduced singlet oxygen and 9,10-dimethylanthracene was performed in homogeneous media and the surface of the composite was not involved in the reaction.

In this work, we present an investigation concerning the evaluation of the catalytic properties of Ni nanoparticles supported on ZrO2, SiO2, and MgAl2O4 for CO2 hydrogenation to methane. The supports were prepared by coprecipitation and sol-gel, while Ni was incorporated by impregnation (10–20 wt %). X-ray diffraction, nitrogen physisorption, temperature-programmed reduction, H2 pulse chemisorption, Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy were the main characterization techniques employed. A laboratory fixed-bed reactor operated at atmospheric pressure, a temperature range of 350–500 °C, and a stoichiometric H2/CO2 molar ratio was used for catalyst evaluation. The most outstanding results were obtained with nickel catalysts supported on ZrO2 with CO2 conversions of close to 60%, and selectivity to methane formation was 100% on a dry basis, with high stability after 250 h of reaction time. The majority presence of tetragonal zirconia, as well as the strong Ni–ZrO2 interaction, were responsible for the high catalytic performance of the Ni/ZrO2 catalysts.

No abstract

A series of cationic dyes, methylene blue (MB), safranin O (SF), toluidine blue (TB), and neutral red (NR), were successfully incorporated into a silica matrix by using ultrasound irradiation during the Stöber process. Several analyses were performed, including scanning dynamic light scattering (DLS), electron microscopy (SEM), nitrogen physisorption, FTIR spectroscopy, UV-vis, and diffuse reflectance spectroscopy. The entrapped dyes on silica were evaluated in singlet oxygen (1O2) generation under visible light irradiation, by means of the photosensitized oxidation of 9,10-dimethylanthracene (DMA). According to the results, the photocatalytic performance of the silica composites was improved, and the leakage of the dye from the particles was suppressed. Among these four different types of dye-doped silica composites, the SiO2-SF composite showed the most efficient delivery of1O2.

ZnO is an exciting material for photocatalysis applications due to its high activity, easy accessibility of raw materials, low production costs, and nontoxic. Several ZnO nano and microstructures can be obtained, such as nanoparticles, nanorods, micro flowers, microspheres, among others, depending on the preparation method and conditions. ZnO is a wide bandgap semiconductor presenting massive recombination of the generated charge carriers, limiting its photocatalytic efficiency and stability. It is common to mix it with metal, metal oxide, sulfides, polymers, and nanocarbon-based materials to improve its photocatalytic behavior. Therefore, ZnO–nanocarbon composites formation has been a viable alternative that leads to new, more active, and stable photocatalytic systems. Mainly, graphene is a well-known two-dimensional material, which could be an excellent candidate to hybridize with ZnO due to its excellent physical and chemical properties (e.g., high specific surface area, optical transmittance, and thermal conductivity, among others). This review analyses ZnO–graphene nanocomposites’ recent advances, addressing the synthesis methods and the resulting structural, morphological, optical, and electronic properties. Moreover, we examine the ZnO–graphene composites’ role in the photocatalytic degradation of organic/inorganic pollutants.

Coupling metal-organic frameworks (MOFs) with inorganic semiconductors has been successfully tested in a variety of photocatalytic reactions. In this work we present the synthesis of TiO2/HKUST-1 composites by grinding, solvothermal, and chemical methods, using different TiO2 loadings. These composites were used as photocatalysts for hydrogen production by the photoreforming of a glycerol-water mixture under simulated solar light. Several characterization techniques were employed, including X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), infrared spectroscopy (FTIR), and time-resolved microwave conductivity (TRMC). A synergetic effect was observed with all TiO2/HKUST-1 composites (mass ratio TiO2/MOF 1:1), which presented higher photocatalytic activity than that of individual components. These results were explained in terms of an inhibition of the charge carrier (hole-electron) recombination reaction after photoexcitation, favoring the electron transfer from TiO2 to the MOF and creating reversible Cu1+/Cu0 entities useful for hydrogen production.

Organic synthesis through semiconductor photocatalysis has become an important research area in photochemistry in the last two decades. Significant examples of organic transformations employed for synthetic purposes are oxidation and reduction reactions, isomerization reactions, C-H bond activations and C-C and C-N bond forming reactions. In this review, the use of irradiated semiconductors and different operation conditions in the reduction of organic compounds is surveyed. Here, the photocatalytic reduction of nitroarenes, aldehydes, ketones and miscellaneous compounds will be discussed. This review is concluded with some perspectives of our group on the directions toward which future research may be aimed.