In intensive care unit: A novel system to study clonal relationship among the isolates-0

Ts.<p><b>Copyright information:</b></p><p>Taken from "in intensive care unit: A novel system to study clonal relationship among the isolates"</p><p>http://www.biomedcentral.com/1471-2334/8/79</p><p>BMC Infectious Diseases 2008;8():79-79.</p><p>Published online 8 Jun 2008</p><p>PMCID:PMC2443154.</p><p></p

An Operando Investigation of (Ni–Fe–Co–Ce)O_<i>x</i> System as Highly Efficient Electrocatalyst for Oxygen Evolution Reaction

The oxygen evolution reaction (OER) is a critical component of industrial processes such as electrowinning of metals and the chlor-alkali process. It also plays a central role in the development of a renewable energy field for generation a solar fuels by providing both the protons and electrons needed to generate fuels such as H₂ or reduced hydrocarbons from CO₂. To improve these processes, it is necessary to expand the fundamental understanding of catalytically active species at low overpotential, which will further the development of electrocatalysts with high activity and durability. In this context, performing experimental investigations of the electrocatalysts under realistic working regimes (i.e., under operando conditions) is of crucial importance. Here, we study a highly active quinary transition-metal-oxide-based OER electrocatalyst by means of operando ambient-pressure X-ray photoelectron spectroscopy and X-ray absorption spectroscopy performed at the solid/liquid interface. We observe that the catalyst undergoes a clear chemical-structural evolution as a function of the applied potential with Ni, Fe, and Co oxyhydroxides comprising the active catalytic species. While CeO₂ is redox inactive under catalytic conditions, its influence on the redox processes of the transition metals boosts the catalytic activity at low overpotentials, introducing an important design principle for the optimization of electrocatalysts and tailoring of high-performance materials

In intensive care unit: A novel system to study clonal relationship among the isolates-2

4 = environmental-sub clone 5; 5 = patient's sub clone 5; 6 = patient's sub clone 6; 7 = patient's sub clone 7; 8 = patient's sub clone 8; 9 = environmental-sub clone 7; 10 = patient's sub clone 1; 11 = patient's sub clone 2; 12 = patient's sub clone 3; 13 = patient's sub clone 4; 14 = patient's sub clone 10; 15 = patient's sub clone 11; 16 = environmental-sub clone 9; 17 = environmental-sub clone 8; 18 = environmental-sub clone 10; 19 = environmental-sub clone 11; 20 = environmental-sub clone 12; 21 = environmental-sub clone 3; 22 = environmental-sub clone 4; 23 = environmental-sub clone 2; 24 = patient's sub clone 12; 25 = patient's sub clone 13; 26 = environmental-sub clone 13; 27 = environmental-sub clone 14; 28 = environmental-sub clone 15.<p><b>Copyright information:</b></p><p>Taken from "in intensive care unit: A novel system to study clonal relationship among the isolates"</p><p>http://www.biomedcentral.com/1471-2334/8/79</p><p>BMC Infectious Diseases 2008;8():79-79.</p><p>Published online 8 Jun 2008</p><p>PMCID:PMC2443154.</p><p></p

In intensive care unit: A novel system to study clonal relationship among the isolates-1

E floor near the patient beds no.1, 3,4 3, 9 = strain cultured from the desk surfaces of beds no.4 and 7; 4 = strain cultured from buttons on the ventilator of bed no.3; 5, 12 = strain cultured from ventilator keyboard of bed no.3 and 6; 7 = strain cultured from edge side of bed no.8; 8 = strain cultured from drawers of the bedside table near bed no.5; 10 = strain cultured from service desk near bed no.1; 13 = strain cultured from the floor at the entrance of ICU; 14 = strain cultured from folder of medical record of patient in the bed no.1. 15 = strain cultured from monitor keyboard of bed no.3.<p><b>Copyright information:</b></p><p>Taken from "in intensive care unit: A novel system to study clonal relationship among the isolates"</p><p>http://www.biomedcentral.com/1471-2334/8/79</p><p>BMC Infectious Diseases 2008;8():79-79.</p><p>Published online 8 Jun 2008</p><p>PMCID:PMC2443154.</p><p></p

Understanding the Oxygen Evolution Reaction Mechanism on CoO_<i>x</i> using <i>Operando</i> Ambient-Pressure X‑ray Photoelectron Spectroscopy

Photoelectrochemical water splitting is a promising approach for renewable production of hydrogen from solar energy and requires interfacing advanced water-splitting catalysts with semiconductors. Understanding the mechanism of function of such electrocatalysts at the atomic scale and under realistic working conditions is a challenging, yet important, task for advancing efficient and stable function. This is particularly true for the case of oxygen evolution catalysts and, here, we study a highly active Co₃O₄/Co­(OH)₂ biphasic electrocatalyst on Si by means of <i>operando</i> ambient-pressure X-ray photoelectron spectroscopy performed at the solid/liquid electrified interface. Spectral simulation and multiplet fitting reveal that the catalyst undergoes chemical-structural transformations as a function of the applied anodic potential, with complete conversion of the Co­(OH)₂ and partial conversion of the spinel Co₃O₄ phases to CoO­(OH) under precatalytic electrochemical conditions. Furthermore, we observe new spectral features in both Co 2p and O 1s core-level regions to emerge under oxygen evolution reaction conditions on CoO­(OH). The <i>operando</i> photoelectron spectra support assignment of these newly observed features to highly active Co⁴⁺ centers under catalytic conditions. Comparison of these results to those from a pure phase spinel Co₃O₄ catalyst supports this interpretation and reveals that the presence of Co­(OH)₂ enhances catalytic activity by promoting transformations to CoO­(OH). The direct investigation of electrified interfaces presented in this work can be extended to different materials under realistic catalytic conditions, thereby providing a powerful tool for mechanism discovery and an enabling capability for catalyst design

Microscopic View on a Chemical Vapor Deposition Route to Boron-Doped Graphene Nanostructures

Single layer boron-doped graphene layers have been grown on polycrystalline copper foils by chemical vapor deposition using methane and diborane as carbon and boron sources, respectively. Any attempt to deposit doped layers in one-step has been fruitless, the reason being the formation of very reactive boron species as a consequence of diborane decomposition on the Cu surface, which leads to disordered nonstoichiometric carbides. However, a two-step procedure has been optimized: as a first step, the surface is seeded with pure graphene islands, while the boron source is activated only in a second stage. In this case, the nonstochiometric boron carbides formed on the bare copper areas between preseeded graphene patches can be exploited to easily release boron, which diffuses from the peripheral areas inward of graphene islands. The effective substitutional doping (of the order of about 1%) has been demonstrated by Raman and photoemission experiments. The electronic properties of doped layers have been characterized by spatially resolved photoemission band mapping carried out on single domain graphene flakes using a photon beam with a spot size of 1 μm. The whole set of experiments allow us to clarify that boron is effective at promoting the anchoring carbon species on the surface. Taking the cue from this basic understanding, it is possible to envisage new strategies for the design of complex 2D graphene nanostructures with a spatially modulated doping

Influence of Excess Charge on Water Adsorption on the BiVO₄(010) Surface

We present a combined computational and experimental study of the adsorption of water on the Mo-doped BiVO4(010) surface, revealing how excess electrons influence the dissociation of water and lead to hydroxyl-induced alterations of the surface electronic structure. By comparing ambient pressure resonant photoemission spectroscopy (AP-ResPES) measurements with the results of first-principles calculations, we show that the dissociation of water on the stoichiometric Mo-doped BiVO4(010) surface stabilizes the formation of a small electron polaron on the VO4 tetrahedral site and leads to an enhanced concentration of localized electronic charge at the surface. Our calculations demonstrate that the dissociated water accounts for the enhanced V4+ signal observed in ambient pressure X-ray photoelectron spectroscopy and the enhanced signal of a small electron polaron inter-band state observed in AP-ResPES measurements. For ternary oxide surfaces, which may contain oxygen vacancies in addition to other electron-donating dopants, our study reveals the importance of defects in altering the surface reactivity toward water and the concomitant water-induced modifications to the electronic structure

Single and Multiple Doping in Graphene Quantum Dots: Unraveling the Origin of Selectivity in the Oxygen Reduction Reaction

Singly and multiply doped graphene oxide quantum dots have been synthesized by a simple electrochemical method using water as solvent. The obtained materials have been characterized by photoemission spectroscopy and scanning tunneling microscopy, in order to get a detailed picture of their chemical and structural properties. The electrochemical activity toward the oxygen reduction reaction of the doped graphene oxide quantum dots has been investigated by cyclic voltammetry and rotating disk electrode measurements, showing a clear decrease of the overpotential as a function of the dopant according to the sequence: N ∼ B > B,N. Moreover, assisted by density functional calculations of the Gibbs free energy associated with every electron transfer, we demonstrate that the selectivity of the reaction is controlled by the oxidation states of the dopants: as-prepared graphene oxide quantum dots follow a two-electron reduction path that leads to the formation of hydrogen peroxide, whereas after the reduction with NaBH_4, the same materials favor a four-electron reduction of oxygen to water

Substrate Grain-Dependent Chemistry of Carburized Planar Anodic TiO₂ on Polycrystalline Ti

Mixtures or composites of titania and carbon have gained considerable research interest as innovative catalyst supports for low- and intermediate-temperature proton-exchange membrane fuel cells. For applications in electrocatalysis, variations in the local physicochemical properties of the employed materials can have significant effects on their behavior as catalyst supports. To assess microscopic heterogeneities in composition, structure, and morphology, a microscopic multitechnique approach is required. In this work, compact anodic TiO₂ films on planar polycrystalline Ti substrates are converted into carbon/titania composites or multiphase titanium oxycarbides through carbothermal treatment in an acetylene/argon atmosphere in a flow reactor. The local chemical composition, structure, and morphology of the converted films are studied with scanning photoelectron microscopy, micro-Raman spectroscopy, and scanning electron microscopy and are related with the crystallographic orientations of the Ti substrate grains by means of electron backscatter diffraction. Different annealing temperatures, ranging from 550 to 850 °C, are found to yield different substrate grain-dependent chemical compositions, structures, and morphologies. The present study reveals individual time scales for the carbothermal conversion and subsequent surface re-oxidation on substrate grains of a given orientation. Furthermore, it demonstrates the power of a microscopic multitechnique approach for studying polycrystalline heterogeneous materials for electrocatalytic applications

Fast One-Pot Synthesis of MoS₂/Crumpled Graphene p–n Nanonjunctions for Enhanced Photoelectrochemical Hydrogen Production

Aerosol processing enables the preparation of hierarchical graphene nanocomposites with special crumpled morphology in high yield and in a short time. Using modular insertion of suitable precursors in the starting solution, it is possible to synthesize different types of graphene-based materials ranging from heteroatom-doped graphene nanoballs to hierarchical nanohybrids made up by nitrogen-doped crumpled graphene nanosacks that wrap finely dispersed MoS₂ nanoparticles. These materials are carefully investigated by microscopic (SEM, standard and HR TEM), diffraction (grazing incidence X-ray diffraction (GIXRD)) and spectroscopic (high resolution photoemission, Raman and UV−visible spectroscopy) techniques, evidencing that nitrogen dopants provide anchoring sites for MoS₂ nanoparticles, whereas crumpling of graphene sheets drastically limits aggregation. The activity of these materials is tested toward the photoelectrochemical production of hydrogen, obtaining that N-doped graphene/MoS₂ nanohybrids are seven times more efficient with respect to single MoS₂ because of the formation of local p–n MoS₂/N-doped graphene nanojunctions, which allow an efficient charge carrier separation