Mineral Particles in Foliar Fertilizer Formulations Can Improve the Rate of Foliar Uptake.

The application of foliar sprays of suspensions of relatively insoluble essential element salts is gradually becoming common, chiefly with the introduction of nano-technology approaches in agriculture. However, there is controversy about the effectiveness of such sparingly soluble nutrient sources as foliar fertilizers. In this work, we focussed on analysing the effect of adding Ca-carbonate (calcite, CaCO) micro- and nano-particles as model sparingly soluble mineral compounds to foliar fertilizer formulations in terms of increasing the rate of foliar absorption.

Impact of Tetrabutylammonium on the Oxidation of Bromide by Ozone.

The reaction of ozone with sea-salt derived bromide is relevant for marine boundary layer atmospheric chemistry. The oxidation of bromide by ozone is enhanced at aqueous interfaces. Ocean surface water and sea spray aerosol are enriched in organic compounds, which may also have a significant effect on this reaction at the interface.

Disordered Adsorbed Water Layers on TiO Nanoparticles under Subsaturated Humidity Conditions at 235 K.

The interaction of water with TiO is of substantial scientific and technological interest as it determines the activity of TiO in photocatalytic and environmental applications in nanoparticle suspensions in water, in complex appliances, or in pure form interacting with water vapor. The influence of TiO nanoparticles on the hydrogen bonding structure of water molecules is an important factor that controls hydration of other species, reactions, or nucleation processes. We use a combination of ambient-pressure X-ray photoelectron spectroscopy and electron yield near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at the oxygen K-edge to investigate the hydrogen bonding structure of adsorbed water on titania nanoparticles in equilibrium with nearly saturated water vapor at 235 K.

The opposing effect of butanol and butyric acid on the abundance of bromide and iodide at the aqueous solution-air interface.

The efficient oxidation of iodide and bromide at the aqueous solution-air interface of the ocean or of sea spray aerosol particles had been suggested to be related to their surface propensity. The ubiquitous presence of organic material at the ocean surface calls for an assessment of the impact of often surface-active organic compounds on the interfacial density of halide ions. We used in situ X-ray photoelectron spectroscopy with a liquid micro-jet to obtain chemical composition information at aqueous solution-vapor interfaces from mixed aqueous solutions containing bromide or iodide and 1-butanol or butyric acid as organic surfactants.

Pre-melting and the adsorption of formic acid at the air-ice interface at 253 K as seen by NEXAFS and XPS.

Interactions between trace gases and ice are important in environmental chemistry and for Earth's climate. In particular, the adsorption of trace gases to ice surfaces at temperatures approaching the melting point has raised interest in the past, because of the prevailing pre-melting. Here, we present Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy data at ambient partial pressure of water to better define the onset temperature of pre-melting at the interfacial region of ice.

The adsorption of silicon on an iridium surface ruling out silicene growth.

The adsorption of Si atoms on a metal surface might proceed through complex surface processes, whose rate is determined differently by factors such as temperature, Si coverage, and metal cohesive energy. Among other transition metals, iridium is a special case since the Ir(111) surface was reported first, in addition to Ag(111), as being suitable for the epitaxy of silicene monolayers. In this study we followed the adsorption of Si on the Ir(111) surface via high resolution core level photoelectron spectroscopy, starting from the clean metal surface up to a coverage exceeding one monolayer, in a temperature range between 300 and 670 K.

A surface-stabilized ozonide triggers bromide oxidation at the aqueous solution-vapour interface.

Oxidation of bromide in aqueous environments initiates the formation of molecular halogen compounds, which is important for the global tropospheric ozone budget. In the aqueous bulk, oxidation of bromide by ozone involves a [Br•OOO] complex as intermediate. Here we report liquid jet X-ray photoelectron spectroscopy measurements that provide direct experimental evidence for the ozonide and establish its propensity for the solution-vapour interface.

Coexistence of Physisorbed and Solvated HCl at Warm Ice Surfaces.

The interfacial ionization of strong acids is an essential factor of multiphase and heterogeneous chemistry in environmental science, cryospheric science, catalysis research and material science. Using near ambient pressure core level X-ray photoelectron spectroscopy, we directly detected a low surface coverage of adsorbed HCl at 253 K in both molecular and dissociated states. Depth profiles derived from XPS data indicate the results as physisorbed molecular HCl at the outermost ice surface and dissociation occurring upon solvation deeper in the interfacial region.

Chemical Composition and Properties of the Liquid-Vapor Interface of Aqueous C1 to C4 Monofunctional Acid and Alcohol Solutions.

The liquid-vapor interface is playing an important role in aerosol and cloud chemistry in cloud droplet activation by aerosol particles and potentially also in ice nucleation. We have employed the surface sensitive and chemically selective X-ray photoelectron spectroscopy (XPS) technique to examine the liquid-vapor interface for mixtures of water and small alcohols or small carboxylic acids (C1 to C4), abundant chemicals in the atmosphere in concentration ranges relevant for cloud chemistry or aerosol particles at the point of activation into a cloud droplet. A linear correlation was found between the headgroup carbon 1s core-level signal intensity and the surface excess derived from literature surface tension data with the offset being explained by the bulk contribution to the photoemission signal.

Introducing Time Resolution to Detect Ce Catalytically Active Sites at the Pt/CeO Interface through Ambient Pressure X-ray Photoelectron Spectroscopy.

X-ray photoelectron spectroscopy has been employed for the qualitative and quantitative characterization of both model and real catalytic surfaces. Recent progress in the detection of photoelectrons has enabled the acquisition of spectra at pressures up to a few tens of millibars. Although reducing the pressure gap represents a remarkable advantage for catalysis, active sites may be short-lived or hidden in the majority of spectator species.

Chemical gating of epitaxial graphene through ultrathin oxide layers.

We achieved a controllable chemical gating of epitaxial graphene grown on metal substrates by exploiting the electrostatic polarization of ultrathin SiO2 layers synthesized below it. Intercalated oxygen diffusing through the SiO2 layer modifies the metal-oxide work function and hole dopes graphene. The graphene/oxide/metal heterostructure behaves as a gated plane capacitor with the in situ grown SiO2 layer acting as a homogeneous dielectric spacer, whose high capacity allows the Fermi level of graphene to be shifted by a few hundreds of meV when the oxygen coverage at the metal substrate is of the order of 0.

Incidence and prognostic significance of new onset atrial fibrillation/flutter in acute pericarditis.

Objective: Data on the incidence of new onset atrial fibrillation and flutter (AF/f) in patients with acute pericarditis are limited. We sought to determine the incidence and prognostic significance of AF/f in this setting.

Methods: Between January 2006 and June 2014, consecutive new cases of acute pericarditis were included in two urban referral centres for pericardial diseases.

Epitaxial growth of a single-domain hexagonal boron nitride monolayer.

We investigate the structure of epitaxially grown hexagonal boron nitride (h-BN) on Ir(111) by chemical vapor deposition of borazine. Using photoelectron diffraction spectroscopy, we unambiguously show that a single-domain h-BN monolayer can be synthesized by a cyclic dose of high-purity borazine onto the metal substrate at room temperature followed by annealing at T=1270 K, this method giving rise to a diffraction pattern with 3-fold symmetry. In contrast, high-temperature borazine deposition (T=1070 K) results in a h-BN monolayer formed by domains with opposite orientation and characterized by a 6-fold symmetric diffraction pattern.

Bottom-up approach for the low-cost synthesis of graphene-alumina nanosheet interfaces using bimetallic alloys.

The production of high-quality graphene-oxide interfaces is normally achieved by graphene growth via chemical vapour deposition on a metallic surface, followed by transfer of the C layer onto the oxide, by atomic layer and physical vapour deposition of the oxide on graphene or by carbon deposition on top of oxide surfaces. These methods, however, come with a series of issues: they are complex, costly and can easily result in damage to the carbon network, with detrimental effects on the carrier mobility. Here we show that the growth of a graphene layer on a bimetallic Ni3Al alloy and its subsequent exposure to oxygen at 520 K result in the formation of a 1.

Oxygen switching of the epitaxial graphene-metal interaction.

Using photoemission spectroscopy techniques, we show that oxygen intercalation is achieved on an extended layer of epitaxial graphene on Ir(111), which results in the "lifting" of the graphene layer and in its decoupling from the metal substrate. The oxygen adsorption below graphene proceeds as on clean Ir(111), giving only a slightly higher oxygen coverage. Upon lifting, the C 1s signal shows a downshift in binding energy, due to the charge transfer to graphene from the oxygen-covered metal surface.

Transfer-free electrical insulation of epitaxial graphene from its metal substrate.

High-quality, large-area epitaxial graphene can be grown on metal surfaces, but its transport properties cannot be exploited because the electrical conduction is dominated by the substrate. Here we insulate epitaxial graphene on Ru(0001) by a stepwise intercalation of silicon and oxygen, and the eventual formation of a SiO(2) layer between the graphene and the metal. We follow the reaction steps by X-ray photoemission spectroscopy and demonstrate the electrical insulation using a nanoscale multipoint probe technique.