Physical characterization of sunflower seeds dehydrated by using electromagnetic induction and low-pressure system

Drying is a widely used food preservation process in which water removal minimizes much of the moisture that causes deterioration reactions that impact the bioproduct quality. The objects of studying are high oleic sunflower seeds which are recognized as a worldwide source of edible oil; consequently, they have significant importance on health and food security. This work presents part of the results of a systematic study to compare the affectations on the several physical parameters of sunflower seeds and kernels with the Thermo-Solar Dehydration method (TSD) compared to Dehydration with Electromagnetic Induction at Low Pressures (DEMILP), finding that the in the last one the time to reach the 8% of the total moisture content was 2.5 times shorter, interesting physical effects and an increment of 5% in the volumetric expansion coefficient, reflected in a reduction of the cut resistance (Dehull) of 0.5KgF significant advantages for the food drying industry

Exceptional oxidation activity with size-controlled supported gold clusters of low atomicity

[EN] The catalytic activity of gold depends on particle size, with the reactivity increasing as the particle diameter decreases. However, investigations into behaviour in the subnanometre regime (where gold exists as small clusters of a few atoms) began only recently with advances in synthesis and characterization techniques. Here we report an easy method to prepare isolated gold atoms supported on functionalized carbon nanotubes and their performance in the oxidation of thiophenol with O-2. We show that single gold atoms are not active, but they aggregate under reaction conditions into gold clusters of low atomicity that exhibit a catalytic activity comparable to that of sulfhydryl oxidase enzymes. When clusters grow into larger nanoparticles, catalyst activity drops to zero. Theoretical calculations show that gold clusters are able to activate thiophenol and O-2 simultaneously, and larger nanoparticles are passivated by strongly adsorbed thiolates. The combination of both reactants activation and facile product desorption makes gold clusters excellent catalysts.Financial support from the Spanish Science and Innovation Ministry (Consolider Ingenio 2010-MULTICAT CSD2009-00050, Subprograma de apoyo a Centros y Universidades de Excelencia Severo Ochoa SEV 2012 0267, MAT2011-28009 and MAT2010-20442 projects) and Xunta de Galicia (Grupos Ref.Comp.2010/41) is acknowledged. M.J.Y. and E. L. acknowledge the support of the National Centre for Research Resources (5 G12RR013646-12) and the National Institute on Minority Health and Health Disparities (G12MD007591) from the National Institutes of Health and of the National Science Foundation for support with grants DMR-1103730 and PREM: NSF PREM Grant # DMR 0934218. We also acknowledge the support of Consejo Nacional De Ciencia y Tecnologia. 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New insights into the chemistry of thiolate-protected palladium nanoparticles

This paper establishes the chemical nature of Pd nanoparticles protected by alkanethiolates that were prepared through a ligand place-exchange approach and the two-phase method, first developed for Au nanoparticles by Brust and Schiffrin. After 10 years since the first study on this kind of Pd nanoparticles was published, the surface composition of the particles is a matter of debate in the literature and it has not been unambiguously assessed. The nanoparticles were studied by means of several techniques: UV–visible spectroscopy, scanning transmission electron microscopy, Fourier-transform infrared spectroscopy, extended X-ray absorption fine structure, and X-ray photoelectron spectroscopy. The experimental data, obtained for the 3 nm diameter Pd particles, prepared by both synthetic routes, are consistent with nanoparticles composed by Pd(0) cores surrounded by a submonolayer of sulfide species, which are protected by alkanethiolates. Also, we unambiguously demonstrate that the chemical nature of these particles is very similar to that experimentally found for alkanethiolate-modified bulk Pd. The results from this paper are important not only for handling thiolate-protected Pd nanoparticles in catalysis and sensing, but also for the basic comprehension of metallic nanoparticles and the relation of their surface structure with the synthesis method.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Ultra-small rhenium clusters supported on graphene

The adsorption of very small rhenium clusters (2-13 atoms) supported on graphene was studied by high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM). The atomic structure of the clusters was fully resolved with the aid of density functional theory calculations and STEM simulations. It was found that octahedral and tetrahedral structures work as seeds to obtain more complex morphologies. Finally, a detailed analysis of the electronic structure suggested that a higher catalytic effect can be expected in Re clusters when adsorbed on graphene than in isolated ones.Fil: Miraflores, Orlando. University of Texas; Estados UnidosFil: Bonafé, Franco Paúl. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Santiago, Ulises. University of Texas; Estados UnidosFil: Larios Rodriguez, Eduardo. Universidad de Sonora; MéxicoFil: Velázquez Salazar, Jesús J.. University of Texas; Estados UnidosFil: Mariscal, Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Yacaman, Miguel José. University of Texas; Estados Unido

Synthesis, characterization, and growth simulations of Cu–Pt bimetallic nanoclusters

Highly monodispersed Cu–Pt bimetallic nanoclusters were synthesized by a facile synthesis approach. Analysis of transmission electron microscopy (TEM) and spherical aberration (Cs)-corrected scanning transmission electron microscopy (STEM) images shows that the average diameter of the Cu–Pt nanoclusters is 3.0 ± 1.0 nm. The high angle annular dark field (HAADF-STEM) images, intensity profiles, and energy dispersive X-ray spectroscopy (EDX) line scans, allowed us to study the distribution of Cu and Pt with atomistic resolution, finding that Pt is embedded randomly in the Cu lattice. A novel simulation method is applied to study the growth mechanism, which shows the formation of alloy structures in good agreement with the experimental evidence. The findings give insight into the formation mechanism of the nanosized Cu–Pt bimetallic catalysts

Modification of TiO2 by bimetallic Au–Cu nanoparticles for wastewater treatment

International audienceAu, Cu and bimetallic Au–Cu nanoparticles were synthesized on the surface of commercial TiO2 compounds (P25) by reduction of the metal precursors with tetrakis(hydroxymethyl) phosphonium chloride (THPC) (0.5% in weight). The alloyed structure of Au–Cu NPs was confirmed by HAADF-STEM, EDS, HRTEM and XPS techniques. The photocatalytic properties of the modified TiO2 have been studied for phenol photodegradation in aqueous suspensions under UV-visible irradiation. The modification by the metal nanoparticles induces an increase in the photocatalytic activity. The highest photocatalytic activity is obtained with Au–Cu/TiO2 (Au–Cu 1 : 3). Their electronic properties have been studied by time resolved microwave conductivity (TRMC) measurements to follow the charge-carrier dynamics. TRMC measurements show that the TiO2 modification with Au, Cu and Au–Cu nanoparticles plays a role in charge-carrier separations increasing the activity under UV-light. Indeed, the metal nanoparticles act as a sink for electrons, decreasing the charge carrier recombination. The TRMC measurements also show that the bimetallic Au–Cu nanoparticles are more efficient in electron scavenging than the monometallic Au and Cu ones