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Find video protocols related to scientific articles indexed in Pubmed.
Comparison of x-ray absorption spectra between water and ice: new ice data with low pre-edge absorption cross-section.
J Chem Phys
PUBLISHED: 07-24-2014
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The effect of crystal growth conditions on the O K-edge x-ray absorption spectra of ice is investigated through detailed analysis of the spectral features. The amount of ice defects is found to be minimized on hydrophobic surfaces, such as BaF2(111), with low concentration of nucleation centers. This is manifested through a reduction of the absorption cross-section at 535 eV, which is associated with distorted hydrogen bonds. Furthermore, a connection is made between the observed increase in spectral intensity between 544 and 548 eV and high-symmetry points in the electronic band structure, suggesting a more extended hydrogen-bond network as compared to ices prepared differently. The spectral differences for various ice preparations are compared to the temperature dependence of spectra of liquid water upon supercooling. A double-peak feature in the absorption cross-section between 540 and 543 eV is identified as a characteristic of the crystalline phase. The connection to the interpretation of the liquid phase O K-edge x-ray absorption spectrum is extensively discussed.
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Different reactivity of the various platinum oxides and chemisorbed oxygen in CO oxidation on Pt(111).
J. Am. Chem. Soc.
PUBLISHED: 04-22-2014
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We have used X-ray photoelectron spectroscopy and polarization-resolved O K-edge X-ray absorption spectroscopy to investigate the reactivity of various oxygen covered Pt(111) surfaces, which emerge under high temperature and pressure conditions, toward CO. We find that the reactivity of the O/Pt(111) system decreases monotonically with increasing oxygen coverage. Of the three surface oxygen phases, viz., chemisorbed oxygen (O(ad)), a PtO-like surface oxide, and ?-PtO2 trilayers, Oad exhibits the highest reactivity toward CO, whereas ?-PtO2 trilayers exhibit the lowest. Pt(111) surfaces fully terminated by ?-PtO2 trilayers are inert to CO. Here it is proposed that the reactive phase is either O(ad) or PtO-like surface oxide phase on bare non-CO poisoned Pt regions with PtO2 as majority spectator species.
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In?situ observation of surface species on iridium oxide nanoparticles during the oxygen evolution reaction.
Angew. Chem. Int. Ed. Engl.
PUBLISHED: 02-11-2014
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An iridium oxide nanoparticle electrocatalyst under oxygen evolution reaction conditions was probed in?situ by ambient-pressure X-ray photoelectron spectroscopy. Under OER conditions, iridium undergoes a change in oxidation state from Ir(IV) to Ir(V) that takes place predominantly at the surface of the catalyst. The chemical change in iridium is coupled to a decrease in surface hydroxide, providing experimental evidence which strongly suggests that the oxygen evolution reaction on iridium oxide occurs through an OOH-mediated deprotonation mechanism.
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Interlayer carbon bond formation induced by hydrogen adsorption in few-layer supported graphene.
Phys. Rev. Lett.
PUBLISHED: 08-20-2013
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We report on the hydrogen adsorption induced phase transition of a few layer graphene (1 to 4 layers) to a diamondlike structure on Pt(111) based on core level x-ray spectroscopy, temperature programed desorption, infrared spectroscopy, and density functional theory total energy calculations. The surface adsorption of hydrogen induces a hybridization change of carbon from the sp2 to the sp3 bond symmetry, which propagates through the graphene layers, resulting in interlayer carbon bond formation. The structure is stabilized through the termination of interfacial sp3 carbon atoms by the substrate. The structural transformation occurs as a consequence of high adsorption energy.
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Highly compressed two-dimensional form of water at ambient conditions.
Sci Rep
PUBLISHED: 01-15-2013
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The structure of thin-film water on a BaF(2)(111) surface under ambient conditions was studied using x-ray absorption spectroscopy from ambient to supercooled temperatures at relative humidity up to 95%. No hexagonal ice-like structure was observed in spite of the expected templating effect of the lattice-matched (111) surface. The oxygen K-edge x-ray absorption spectrum of liquid thin-film water on BaF(2) exhibits, at all temperatures, a strong resemblance to that of high-density phases for which the observed spectroscopic features correlate linearly with the density. Surprisingly, the highly compressed, high-density thin-film liquid water is found to be stable from ambient (300 K) to supercooled (259 K) temperatures, although a lower-density liquid would be expected at supercooled conditions. Molecular dynamics simulations indicate that the first layer water on BaF(2)(111) is indeed in a unique local structure that resembles high-density water, with a strongly collapsed second coordination shell.
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Lattice-strain control of the activity in dealloyed core-shell fuel cell catalysts.
Nat Chem
PUBLISHED: 03-11-2010
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Electrocatalysis will play a key role in future energy conversion and storage technologies, such as water electrolysers, fuel cells and metal-air batteries. Molecular interactions between chemical reactants and the catalytic surface control the activity and efficiency, and hence need to be optimized; however, generalized experimental strategies to do so are scarce. Here we show how lattice strain can be used experimentally to tune the catalytic activity of dealloyed bimetallic nanoparticles for the oxygen-reduction reaction, a key barrier to the application of fuel cells and metal-air batteries. We demonstrate the core-shell structure of the catalyst and clarify the mechanistic origin of its activity. The platinum-rich shell exhibits compressive strain, which results in a shift of the electronic band structure of platinum and weakening chemisorption of oxygenated species. We combine synthesis, measurements and an understanding of strain from theory to generate a reactivity-strain relationship that provides guidelines for tuning electrocatalytic activity.
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Tuning the metal-adsorbate chemical bond through the ligand effect on platinum subsurface alloys.
Angew. Chem. Int. Ed. Engl.
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Scratching beneath the surface: Pt-M(3d)-Pt(111) (M(3d) = Co, Ni) bimetallic subsurface alloys have been designed to show the ligand effect tunes reactivity in oxygen and hydrogen adsorption systems. The platinum-oxygen bond order was investigated by oxygen atom projection in the occupied and unoccupied space using X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS).
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What is Visualize?

JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

How does it work?

We use abstracts found on PubMed and match them to JoVE videos to create a list of 10 to 30 related methods videos.

Video X seems to be unrelated to Abstract Y...

In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.