Effect of gold electronic state on the catalytic performance of nano gold catalysts in n-octanol oxidation

UIDB/50006/2020 project VIU-RSCBMT-65/2019 project 18-29-24037 (Russia) MINECO project CTQ2017-86170-R (Spain)This study aims to identify the role of the various electronic states of gold in the catalytic behavior of Au/MxOy/TiO2 (where MxOy are Fe2O3 or MgO) for the liquid phase oxidation of n-octanol, under mild conditions. For this purpose, Au/MxOy/TiO2 catalysts were prepared by deposition-precipitation with urea, varying the gold content (0.5 or 4 wt.%) and pretreatment conditions (H2 or O2), and characterized by low temperature nitrogen adsorption-desorption, X-ray powder diffraction (XRD), energy dispersive spectroscopy (EDX), scanning transmission electron microscopy-high angle annular dark field (STEM HAADF), diffuse reflectance Fourier transform infrared (DRIFT) spectroscopy of CO adsorption, temperature-programmable desorption (TPD) of ammonia and carbon dioxide, and X-ray photoelectron spectroscopy (XPS). Three states of gold were identified on the surface of the catalysts, Au0, Au1+ and Au3+, and their ratio determined the catalysts performance. Based on a comparison of catalytic and spectroscopic results, it may be concluded that Au+ was the active site state, while Au0 had negative effect, due to a partial blocking of Au0 by solvent. Au3+ also inhibited the oxidation process, due to the strong adsorption of the solvent and/or water formed during the reaction. Density functional theory (DFT) simulations confirmed these suggestions. The dependence of selectivity on the ratio of Brønsted acid centers to Brønsted basic centers was revealed.publishersversionpublishe

Study of the Affinity between the Protein Kinase PKA and Peptide Substrates Derived from Kemptide Using Molecular Dynamics Simulations and MM/GBSA

Vergara-Jaque, A (Vergara-Jaque, Ariela); Poblete, H (Poblete, Horacio); Caballero, J (Caballero, Julio) Univ Talca, Fac Ingn, Ctr Bioinformat & Simulac Mol, Talca, ChileWe have carried out a protocol in computational biochemistry including molecular dynamics (MD) simulations and MM/GBSA free energy calculations on the complex between the protein kinase A (PKA) and the specific peptide substrate Kemptide (LRRASLG). We made the same calculations on other PKA complexes that contain Kemptide derivatives (with mutations of the arginines, and with deletions of N and C-terminal amino acids). We predicted shifts in the free energy changes from the free PKA to PKA-substrate complex (DDGERES) when Kemptide structure is modified (we consider that the calculated shifts correlate with the experimental shifts of the free energy changes from the free PKA to the transition states (DDGERTS) determined by the catalytic efficiency (kcat/KM) changes). Our results demonstrate that it is possible to predict the kinetic properties of protein kinases using simple computational biochemistry methods. As an additional benefit, these methods give detailed molecular information that permit the analysis of the atomic forces that contribute to the affinity between protein kinases and their substrates

Photocatalytic hydrogen production over titania modified by gold – Metal (palladium, nickel and cobalt) catalysts

The photocatalytic production of hydrogen on modified Au/TiO2-based photocatalysts by using water/methanol mixtures was studied. The main goal was to study the effect of surface modification of Au/TiO2 with Pd, Ni and Co on H2 production under UV light irradiation (λ ca. 254 nm). Catalysts were produced by depositing Pd, Ni or Co precursors (nitrates hydrated salts) on TiO2 (Evonik, P25) by incipient wetness impregnation followed by thermal treatment under H2 (Pd and Co) or air (Ni). Thereafter, Au was incorporated by deposition-precipitation with urea (DPU method) and then the catalysts were thermally activated again under air flow. The photocatalysts were characterized by UV?Vis diffuse reflectance, HAADF-TEM, EDXS, FTIR CO adsorption, XPS and photoluminescence. In order to obtain detailed information about the composition of the nanoparticles, high-resolution elemental analyses (EDXS line scans) were performed. The Au-Pd, Au-Ni and Au-Co on TiO2 photocatalysts showed higher performance for H2 production (266, 256 and 171 mmol H2 mmolAu −1 h−1, respectively) compared to the Au/TiO2 material (106 mmol H2 mmolAu −1 h−1). PL results showed that the improved H2 production rate could be explained by an enhanced charge separation. The highest H2 production showed by the Au-Pd/TiO2 sample could be attributed to synergistic effects, derived from the interaction between Au and Pd particles. For the Au-Ni/TiO2 and Au-Co/TiO2 samples it is proposed that nickel or cobalt oxides worked as promoters (with additives effects) because of the formation of a p-n heterojunction.Fil: Barrios, Celina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina. Universidad Nacional Autónoma de México; MéxicoFil: Albiter, E.. Universidad Nacional Autónoma de México; MéxicoFil: Gracia y Jimenez, J. M.. Benemérita Universidad Autónoma de Puebla; MéxicoFil: Tiznado, H.. Universidad Nacional Autónoma de México; MéxicoFil: Romo Herrera, J.. Universidad Nacional Autónoma de México; MéxicoFil: Zanella, R.. Universidad Nacional Autónoma de México; Méxic

Fabrication of macro-mesoporous zirconia-alumina materials with a one-dimensional hierarchical structure

A series of one dimensional (1D) zirconia/alumina nanocomposites were prepared by the deposition of zirconium species onto the 3D framework of boehmite nanofibres formed by dispersing boehmite nanofibres into butanol solution. The materials were calcined at 773K and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), N2 adsorption/desorption, infrared emission spectroscopy (IES). The results demonstrated that when the molar percentage X=100*Zr/(Al+Zr) was > 30 %, extremely long ZrO2/Al2O3 composite nanorods with evenly distributed ZrO2 nanocrystals on the surface were formed. The stacking of such nanorods gave rise to a new kind of macroporous material without the use of any organic space filler\template or other specific technologies. The mechanism for the formation of long ZrO2/Al2O3 composite nanorods was proposed in this work

Dual-photosensitizer coupled nanoscintillator capable of producing type I and type II ROS for next generation photodynamic therapy

The current photodynamic therapy (PDT) is majorly hindered by the shallow penetration depth and oxygen dependency, limiting its application to deep-seated solid hypoxic tumors. Thus, it is meaningful to develop efficient X-ray mediated PDT system capable of generating reactive oxygen species (ROS) under both the normoxic and hypoxic conditions. Herein, we report the synthesis and characterization of nanocomposite, YAG:Pr@ZnO@PpIX with an amalgamation of UV-emitting Y2.99Pr0.01Al5O12 (YAG:Pr) nanoscintillator, and zinc oxide (ZnO) and protoporphyrin IX (PpIX) as photosensitizers. YAG:Pr surface was coated with a ZnO layer (∼10 nm) by atomic layer deposition, and then PpIX was covalently conjugated via a linker to give YAG:Pr@ZnO@PpIX. The photo- and cathodoluminescence analyses gave the evidences of efficient energy transfer from YAG:Pr to ZnO at ∼320 nm, and YAG:Pr@ZnO to PpIX at Soret region (350–450 nm). The nanohybrid was able to produce both, Type I and Type II ROS upon direct and indirect photoactivation with UV365nm and UV290nm, respectively. In vitro cytotoxicity of non-activated YAG:Pr@ZnO@PpIX in mouse melanoma cells revealed low toxicity, which significantly enhanced upon photoactivation with UV365nm indicating the photokilling property of the nanohybrid. Overall, our preliminary studies successfully demonstrate the potential of YAG:Pr@ZnO@PpIX to overcome the limited penetration and oxygen-dependency of traditional PDT