The efficiency of polymer electrolyte membrane fuel cells is strongly depending on the electrocatalyst performance, that is, its activity and stability. We have designed a catalyst material that ...combines both, the high activity for the decisive cathodic oxygen reduction reaction associated with nanoscale Pt alloys, and the excellent durability of an advanced nanostructured support. Owing to the high specific activity and large active surface area, the catalyst shows extraordinary mass activity values of 1.0 A mgPt−1. Moreover, the material retains its initial active surface area and intrinsic activity during an extended accelerated aging test within the typical operation range. This excellent performance is achieved by confined‐space alloying of the nanoparticles in a controlled manner in the pores of the support.
Forever young catalysts: An excellently performing electrocatalyst for the oxygen reduction reaction (ORR) is prepared by confined‐space alloying of nanoparticles in the pores of a carbon support. Owing to the high specific activity and the small particle size even after thermal annealing, the catalyst has a high mass activity. The nanoparticles are also highly stable in accelerated aging tests.
The production and use of nanoparticles (NPs) in different fields increased in the last years. However, some NPs have toxicological properties, making these materials potential emerging pollutants. ...Therefore, it is important to investigate the uptake, transformation, translocation, and deposition of NPs in plants. In this work, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and micro X-ray fluorescence (μ-XRF) were used to investigate the uptake and translocation of La2O3 NPs to stem and leaves of Pfaffia glomerata (Spreng.) Pedersen after in vitro cultivation of plants in the presence of 400 mg L–1 of La2O3 NPs. By using LA-ICP-MS and μ-XRF, image of the spatial distribution of La in the leaves was obtained, where higher concentration of La was observed in the main veins. Differences in the signal profile of La in leaves of plants cultivated in the presence of bulk La2O3 (b-La2O3) and La2O3 NPs were observed. Sharp peaks of La indicated that NPs were transported to the stems and leaves of plants treated with La2O3 NPs. Both LA-ICP-MS and μ-XRF techniques have shown to be useful for detecting NPs in plants, but LA-ICP-MS is more sensitive than μ-XRF and allowed better detection and visualization of La distribution in the whole leaf.
Recently, the ANITA collaboration reported on two upward-going extensive air shower events consistent with a primary particle that emerges from the surface of the Antarctic ice sheet. These events ...may be of ν τ origin, in which the neutrino interacts within the Earth to produce a τ lepton that emerges from the Earth, decays in the atmosphere, and initiates an extensive air shower. In this paper we estimate an upper bound on the ANITA acceptance to a diffuse ν τ flux detected via τ -lepton-induced air showers within the bounds of standard model uncertainties. By comparing this estimate with the acceptance of Pierre Auger Observatory and IceCube and assuming standard model interactions, we conclude that a ν τ origin of these events would imply a neutrino flux at least two orders of magnitude above current bounds.
Understanding the mechanisms of absorption and transport of foliar nutrition is a key step towards the development of advanced fertilization methods. This study employed X-ray fluorescence (XRF) and ...X-ray absorption near edge spectroscopy (XANES) to trace the in vivo absorption and transport of ZnO and ZnSO4(aq) to soybean leaves (Glycine max). XRF maps monitored over 48 h showed a shape change of the dried ZnSO4(aq) droplet, indicating Zn2+ absorption. Conversely, these maps did not show short movement of Zn from ZnO. XRF measurements on petioles of leaves that received Zn2+ treatments clarified that the Zn absorption and transport in the form of ZnSO4(aq) was faster that of ZnO. Solubility was the major factor driving ZnSO4(aq) absorption. XANES speciation showed that in planta Zn is transported coordinated with organic acids. Because plants demand Zn during their entire lifecycle, the utilization of sources with different solubilities can increase Zn use efficiency.
An in-depth understanding of the active site requires advanced operando techniques and the preparation of defined catalysts. We elucidate here the mechanism of the selective catalytic reduction of NO ...by NH3 (NH3–SCR) over a Fe-ZSM-5 zeolite catalyst. 1.3 wt % Fe-ZSM-5 with low nuclearity Fe sites was synthesized, tested in the SCR reaction and characterized by UV–vis, X-ray absorption near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) spectroscopy. Next, this defined Fe-zeolite catalyst was studied by complementary high-energy-resolution fluorescence-detected XANES (HERFD-XANES) and valence-to-core X-ray emission spectroscopy (V2C XES) under different model in situ and realistic working (operando) conditions identical to the catalyst test bench including the presence of water vapor. HERFD-XANES uncovered that the coordination (between 4 and 5), geometry (tetrahedral, partly 5-fold), and oxidation state of the Fe centers (reduced in NH3, partly in SCR mixture, slight reduction in NO) strongly changed. V2C XES supported by DFT calculations provided important insight into the chemical nature of the species adsorbed on Fe sites. The unique combination of techniques applied under realistic reaction conditions and the corresponding catalytic data unraveled the adsorption of ammonia via oxygen on the iron site. The derived reaction model supports a mechanism where adsorbed NO x reacts with ammonia coordinated to the Fe3+ site yielding Fe2+ whose reoxidation is slow.
A nanodispersed intermetallic GaPd2/SiO2 catalyst is prepared by simple impregnation of industrially relevant high-surface-area SiO2 with Pd and Ga nitrates, followed by drying, calcination, and ...reduction in hydrogen. The catalyst is tested for CO2 hydrogenation to methanol at ambient pressure, revealing that the intrinsic activity of the GaPd2/SiO2 is higher than that of the conventional Cu/ZnO/Al2O3, while the production of the undesired CO is lower. A combination of complementary in situ and ex situ techniques are used to investigate the GaPd2/SiO2 catalyst. In situ X-ray diffraction and in situ extended X-ray absorption fine structure spectroscopy show that the GaPd2 intermetallic phase is formed upon activation of the catalyst via reduction and remains stable during CO2 hydrogenation. Identical location–transmission electron microscopy images acquired ex situ (i.e., micrographs of exactly the same catalyst area recorded at the different steps of activation and reaction procedure) show that nanoparticle size and dispersion are defined upon calcination with no significant changes observed after reduction and methanol synthesis. Similar conclusions can be drawn from electron diffraction patterns and images acquired using environmental TEM (ETEM), indicating that ETEM results are representative for the catalyst treated at ambient pressure. The chemical composition and the crystalline structure of the nanoparticles are identified by scanning TEM energy dispersive X-ray spectroscopy, selected area electron diffraction, and atomically resolved TEM images.
Global brands are faced with the challenge of conveying concepts that not only are consistent across borders but also resonate with consumers of different cultures. Building on prior research ...indicating that abstract brand concepts induce more favorable consumer responses than functional attributes, the authors introduce a generalizable and robust structure of abstract brand concepts as representations of human values. Using three empirical studies conducted with respondents from eight countries, they demonstrate that this proposed structure is particularly useful for predicting (1) brand meanings that are compatible (vs. incompatible) with each other and, consequently, more (less) favorably accepted by consumers when added to an already established brand concept; (2) brand concepts that are more likely to resonate with consumers with differing cultural orientations; and (3) consumers' responses to attempts to imbue an established brand concept with new, (in) compatible abstract meanings as a function of their own cultural orientations.
Abstract
Understanding nanoparticle root uptake and root-to-shoot transport might contribute to the use of nanotechnology in plant nutrition. This study performed time resolved experiments to probe ...Zn uptake, biotransformation and physiological effects on
Phaseolus vulgaris
(L.). Plants roots were exposed to ZnO nanoparticles (40 and 300 nm) dispersions and ZnSO
4(aq)
(100 and 1000 mg Zn L
−1
) for 48 h. Near edge X-ray absorption spectroscopy showed that 40 nm ZnO was more easily dissolved by roots than 300 nm ZnO. It also showed that in the leaves Zn was found as a mixture Zn
3
(PO
4
)
2
and Zn-histidine complex. X-ray fluorescence spectroscopy showed that root-to-shoot Zn-translocation presented a decreasing gradient of concentration and velocity, it seems radial Zn movement occurs simultaneously to the axial xylem transport. Below 100 mg Zn L
−1
, the lower stem tissue section served as a buffer preventing Zn from reaching the leaves. Conversely, it was not observed for 1000 mg Zn L
−1
ZnSO
4(aq)
. Transcriptional analysis of genes encoding metal carriers indicated higher expression levels of tonoplast-localized transporters, suggesting that the mechanism trend to accumulate Zn in the lower tissues may be associated with an enhanced of Zn compartmentalization in vacuoles. The photosynthetic rate, transpiration, and water conductance were impaired by treatments.
▶ The depth and surface Cu dopant concentration can be modulated by thermal treatment of TiO2. ▶ H2O2 can be degraded by TiO2 electron/hole pair as well as by Cu metallic and ionic species, trough of ...a Like-Fenton mechanism. ▶ The colorant degradation occurs due successive hydoxylations.
In this work the effect of doping concentration and depth profile of Cu atoms on the photocatalytic and surface properties of TiO2 films were studied. TiO2 films of about 200nm thickness were deposited on glass substrates on which a thin Cu layer (5nm) was deposited. The films were annealed during 1s to 100°C and 400°C, followed by chemical etching of the Cu film. The grazing incidence X-ray fluorescence measurements showed a thermal induced migration of Cu atoms to depths between 7 and 31nm. The X-ray photoelectron spectroscopy analysis detected the presence of TiO2, Cu2O and Cu0 phases and an increasing Cu content with the annealing temperature. The change of the surface properties was monitored by the increasing red-shift and absorption of the ultraviolet–visible spectra. Contact angle measurements revealed the formation of a highly hydrophilic surface for the film having a medium Cu concentration. For this sample photocatalytic assays, performed by methylene blue discoloration, show the highest activity. The proposed mechanism of the catalytic effect, taking place on Ti/Cu sites, is supported by results obtained by theoretical calculations.
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