8,789 research outputs found
Graphene: Microwave Enabled One‐Pot, One‐Step Fabrication and Nitrogen Doping of Holey Graphene Oxide for Catalytic Applications (Small 27/2015)
No full textPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/112226/1/smll201570159.pd
Direct Production of Graphene Nanosheets for Near Infrared Photoacoustic Imaging.
No full textHummers method is commonly used for the fabrication of graphene oxide (GO) from graphite particles. The oxidation process also leads to the cutting of graphene sheets into small pieces. From a thermodynamic perspective, it seems improbable that the aggressive, somewhat random oxidative cutting process could directly result in graphene nanosheets without destroying the intrinsic π-conjugated structures and the associated exotic properties of graphene. In Hummers method, both KMnO4 and NO2þ (nitronium ions) in concentrated H2SO4 solutions act as oxidants via different oxidation mechanisms. From both experimental observations and theoretical calculations, it appears that KMnO4 plays a major role in the observed oxidative cutting and unzipping processes. We find that KMnO4 also limits nitronium oxidative etching of graphene basal planes, therefore slowing down graphene fracturing processes for nanosheet fabrication. By intentionally excluding KMnO4 and exploiting pure nitronium ion oxidation, aided by the unique thermal and kinetic effects induced by microwave heating, we find that graphite particles can be converted into graphene nanosheets with their π-conjugated aromatic structures and properties largely retained. Without the need of any postreduction processes to remove the high concentration of oxygenated groups that results from Hummers GO formation, the graphene nanosheets as-fabricated exhibit strong absorption, which is nearly wavelength-independent in the visible and near-infrared (NIR) regions, an optical property typical for intrinsic graphene sheets. For the first time, we demonstrate that strong photoacoustic signals can be generated from these graphene nanosheets with NIR excitation. The photo-to-acoustic conversion is weakly dependent on the wavelength of the NIR excitation, which is different from all other NIR photoacoustic contrast agents previously reported.This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in ACS Nano, copyright © American Chemical Society after peer review. To access the final edited and published work see https://dx.doi.org/10.1021/nn403429v
P-Doped Porous Carbon as Metal Free Catalysts for Selective Aerobic Oxidation with an Unexpected Mechanism
No full textAn extremely simple and rapid (seconds) approach is reported to directly synthesize gram quantities of P-doped graphitic porous carbon materials with controlled P bond configuration. For the first time, it is demonstrated that the P-doped carbon materials can be used as a selective metal free catalyst for aerobic oxidation reactions. The work function of P-doped carbon materials, its connectivity to the P bond configuration, and the correlation with its catalytic efficiency are studied and established. In direct contrast to N-doped graphene, the P-doped carbon materials with higher work function show high activity in catalytic aerobic oxidation. The selectivity trend for the electron donating and withdrawing properties of the functional groups attached to the aromatic ring of benzylic alcohols is also different from other metal free carbon based catalysts. A unique catalytic mechanism is demonstrated, which differs from both GO and N-doped graphene obtained by high temperature nitrification. The unique and unexpected catalytic pathway endows the P-doped materials with not only good catalytic efficiency but also recyclability. This, combined with a rapid, energy saving approach that permits fabrication on a large scale, suggests that the P-doped porous materials are promising materials for “green catalysis” due to their higher theoretical surface area, sustainability, environmental friendliness and low cost.This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Nano, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acsnano.5b07054.Peer reviewe
ROSENTHAL, Eric Inventory of documents
No full textCOVERAGE 1904; 1 File; 011 metre.Private papers of Eric Rosenthal, author, journalist and broadcaster
Coordination Geometry and Oxidation State Requirements of Corner Sharing MnO6 Octahedra for Water Oxidation Catalysis: An Investigation of Manganite (γ-MnOOH)
No full textSurface-directed corner-sharing MnO¬6 octahedra within numerous manganese oxide compounds containing Mn3+ or Mn4+ oxidation states show strikingly different catalytic activities for water oxidation, paradoxically poorest for Mn4+ oxides, regardless of oxidation assay (photochemical and electrochemical). This is demonstrated herein by comparing crystalline oxides consisting of Mn3+ (manganite, γ-MnOOH and bixbyite, Mn2O3), Mn4+ (pyrolusite, β-MnO2) and multiple monophasic mixed-valence manganese oxides. Like all Mn4+ oxides, pure β-MnO2 has no detectable catalytic activity, while γ-MnOOH (tetragonally distorted Mn3+O6, D4h symmetry) is significantly more active, and Mn2O3 (trigonal antiprismatic Mn3+O6, D3d symmetry) is the most active. γ-MnOOH deactivates during catalytic turnover simultaneous with the disappearance of crystallographically defined corner-sharing Mn3+O6 and the appearance of Mn4+. Comparing 2D-layered crystalline birnessites (δ-MnO2), the monovalent Mn4+ form is catalytically inert, while the hexagonal polymorph, containing few out-of-layer corner-sharing Mn3+O6, has ~10-fold higher catalytic activity than the triclinic polymorph, containing in-plane edge-sharing Mn3+O6. These electronic and structural correlations point towards the more flexible (corner shared) Mn3+O6 sites, over more rigid (edge shared) sites as substantially more active catalytic centers. Electrochemical measurements show and ligand field theory predicts that among corner shared Mn3+O6 sites, those possessing D3d ligand field symmetry have stronger covalent Mn-O bonding to the six equivalent oxygen ligands, which we ascribe as responsible for more efficient and faster electrolytic water oxidation. By contrast, D4h Mn3+O6 sites have weaker Mn-O bonding to the two axial oxygen ligands, separated electrochemical oxidation waves for Mn and O, and are catalytically less efficient and exhibit slower catalytic turnover. By controlling the ligand field geometry and strength to oxygen ligands we have identified the key variables for tuning water oxidation activity by manganese oxides. We apply these findings to propose a mechanism for water oxidation by the CaMn4O5 catalytic site of natural photosynthesis.This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Catalysis, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://dx.doi.org/10.1021/acscatal.6b00099.Peer reviewe
tritrophic-dispersal-model: Code used for creating figures for "Non-hierarchical dispersal promotes stability and resilience in a tri-trophic metacommunity"
No full text<p>This is the commented code used for creating figures for the paper. Any questions regarding the code should be directed to the corresponding author and repository owner (Eric Pedersen). </p>
Eric Velazquez Spanish Language Picture Book Award 2022 Acceptance Speech
No full textAuthor Eric Velazquez gives his Silver Medal acceptance speech for Pulpo Guisado (Holiday House)https://educate.bankstreet.edu/spanishlanguageaward/1001/thumbnail.jp
Eric C. Lincoln, Professor of Sociology and Religion, 1971
No full textThis is an interview with Eric C. Lincoln. Eric was a Professor of Sociology and religion, Union Theological Seminary and author of many books and articles on Negro history. In this recording the contributors discuss local memphis politics, sociology, and race relations compared to that of other cities in the South and the rest of the country
Interview with Eric Bentley, author, drama critic, and playwright
No full textDistinguished drama critic and Bertolt Brecht scholar, Eric Bentley is interviewed by WTMJ-TV host Jim Peck and John B. Fuegi, associate professor of Comparative Literature. Bentley recalls his association with Brecht, the critical and creative aspects of literature, and his interest in writing plays for the theater.GrayscaleSoun
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