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Dendritic platinum-copper bimetallic nanoassemblies with tunable composition and structure： Arginine-driven self-assembly and enhanced electrocatalytic activity

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Nano Research 2016年第3期9卷 755-765页

作者： Gengtao Fu Huimin Liu Nika You Jiayan Wu Dongmei Sun Lin Xu Yawen Tang Yu Chen Key Laboratory of Macromolecular Science of Shaanxi Province School of Materials Science and Engineering Shaanxi Normal University Xi'an 710062 China Jiangsu Key Laboratory of New Power Batteries Jiangsu Collaborative Innovation Centre of Biomedical Functional Materials School ot Chemistry and Materials Science Nanjing Normal University Nanjing 210023 China Materials Science and Engineering Program & Texas Materials Institute The University of Texas atAustin Austin Texas 78712 USA

Novel self-assembled architectures have received a growing amount of attention and have significant potential for application in catalysis/electrocatalysis. Herein, we take advantage of the unique coordination and self-assembly properties of arginine for the preparation of dendritic PtCu bimetallic nanoassemblies with tunable chemical composition and structure. Strong interactions between the arginine molecules are key in driving the self-assembly of primary nanocrystals. In addition, the strong coordination interactions between arginine and metal ions is responsible for the formation of Pt-Cu alloys. We also investigated the electrocatalytic activity of various dendritic PtCu bimetallic nanoassemblies towards the methanol oxidation reaction. PtBCUl nanoassemblies exhibited excellent electrocatalytic activity and stability in comparison with other PtCu bimetallic nanoassemblies （PtlCu3, PtlCu~） and commercial Pt black, due to their unique dendritic structures and the synergistic effect between the Pt and Cu atoms.

关键词： platinum-copper nanoassemblies arginine molecules electrocatalysis methanol oxidation

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Spatial dependence of polycyclic aromatic compounds growth in counterflow flames

arXiv

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arXiv 2017年

作者： Wang, Qi Elvati, Paolo Kim, Doohyun Olof Johansson, K. Schrader, Paul E. Michelsen, Hope A. Wilson, Kevin R. Violi, Angela Department of Mechanical Engineering University of Michigan 2350 Hayward St. 2250 G.G. Brown Ann ArborMI48109-2125 United States Combustion Research Facility Sandia National Laboratories LivermoreCA94550 United States Chemical Sciences Division Lawrence Berkeley National Laboratory BerkeleyCA94720 United States Departments of Chemical Engineering Biomedical Engineering Macromolecular Science and Engineering Biophysics Program University of Michigan Ann ArborMI United States

The formation mechanisms of aromatic compounds in flame are strongly influenced by the chemical and thermal history that leads to their formation. Indeed, the complex environments that characterize combustion systems do not only affect the composition of gas-phase species, but they also determine the structure and the characteristics of the soot precursors generated. To illustrate the importance of these effects, in this work we investigate the growth mechanisms of soot precursors in an atmospheric-pressure ethylene/oxygen/argon counterflow diffusion flame, using a combination of computational and experimental techniques. In diffusion flames, flow characteristics play an important role in the formation, growth, and oxidation of particles, and soot precursors are strongly affected by the flame location. Fluid dynamics simulations and stochastic discrete modeling were employed together to identify key reaction pathways along various flow streamlines. The models were validated with experimental mass spectra obtained using aerosol mass spectrometry coupled with vacuum-ultraviolet photoionization. Results show that both the hydrogen-abstraction-acetylene-addition mechanism and oxygen-insertion reactions are responsible for the molecular growth, and their relative importance is determined by the flame conditions along the streamlines. Oxygenated species were detected in regions of high temperature, high atomic oxygen concentration, and relatively low acetylene abundance. This study also emphasizes the need to model the counterflow flame in three dimensions to capture the spatial dependence on growth mechanisms of soot precursors. Copyright © 2017, The Authors. All rights reserved.

关键词： Ethylene

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The Influence of Chemical Modification on Linker Rotational Dynamics in Metal–Organic Frameworks

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Angewandte Chemie 2018年第28期130卷

作者： Joshua T. Damron Jialiu Ma Ricardo Kurz Kay Saalwächter Adam J. Matzger Ayyalusamy Ramamoorthy Department of Chemistry University of Michigan 930 N. University Ave. Ann Arbor MI 48109-1055 USA Institut für Physik-NMR Halle/Saale Germany Macromolecular Science and Engineering University of Michigan 2300 Hayward Avenue Ann Arbor MI 48109-1055 USA Biophysics Program University of Michigan 930 N. University Ave. Ann Arbor MI 48109-1055 USA

The robust synthetic flexibility of metal–organic frameworks (MOFs) offers a promising class of tailorable materials, for which the ability to tune specific physicochemical properties is highly desired. This is achievable only through a thorough description of the consequences for chemical manipulations both in structure and dynamics. Magic angle spinning solid‐state NMR spectroscopy offers many modalities in this pursuit, particularly for dynamic studies. Herein, we employ a separated‐local‐field NMR approach to show how specific intraframework chemical modifications to MOF UiO‐66 heavily modulate the dynamic evolution of the organic ring moiety over several orders of magnitude.

关键词： DFT-Rechnungen Dynamik Metall-organische Gerüste Mikroporöse Materialien NMR-Spektroskopie

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Gradient sequence π-conjugated copolymers

Gradient sequence π-conjugated copolymers

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作者： Palermo, Edmund F. McNeil, Anne J. Department of Chemistry and Macromolecular Science and Engineering Program University of Michigan 930 North University Avenue Ann ArborMI48109-1055 United States

ISBN: (纸本)9780841230019

Gradient sequence copolymers exhibit a gradual change in comonomer composition along the polymer chain. These novel materials are interesting because they exhibit unique properties compared to their random, alternating and block copolymer counterparts. We describe herein the synthesis and characterization of the first π-conjugated gradient sequence copolymers, which have only recently been accessible via a controlled, chain-growth synthetic method. We demonstrate that the gradient sequence copolymers exhibit unique thermal, optical and morphological properties compared to the analogous block and random copolymers. In addition, we show that gradient sequence copolymers can act as additives to modulate the thin film morphologies and phase separation behavior of polymer/polymer and polymer/fullerene blends. The impact of gradient sequence copolymer-based additives in stabilizing bulk heterojunction organic solar cells is also described. © 2014 American Chemical Society.

关键词： Phase separation

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Comparisons and development of electrochemical sensors using G-PANI composite based on filter paper and transparency film substrate

Comparisons and development of electrochemical sensors using...

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Nanotechnology 2014: Graphene, CNTs, Particles, Films and Composites - 2014 NSTI Nanotechnology Conference and Expo, NSTI-Nanotech 2014

作者： Ruecha, N. Rodthongkum, N. Cate, D.M. Chailapakul, O. Henry, C.S. Program in Macromolecular Science Faculty of Science Chulalongkorn University Pathumwan Bangkok 10330 Thailand Metallurgy and Materials Science Research Institute Chulalongkorn University Pathumwan Bangkok 10330 Thailand School of Biomedical Engineering Colorado State University Fort Collins CO 80523 United States Electrochemistry and Optical Spectroscopy Research Unit Department of Chemistry Chulalongkorn University Pathumwan Bangkok 10330 Thailand Department of Chemistry Colorado State University Fort Collins CO 80523 United States

ISBN: (纸本)9781482258264

Electrochemical sensors based on filter paper and transparency film substrates have been prepared using screen-printing method for the detection of the heavy metals ions including Pb2+, Cd2+ and Zn 2+. The electrochemical characteristics of these electrodes were analyzed using cyclic voltammetry (CV) and anodic stripping voltammetry (ASV) while the surface roughness were measured using an optical profilometer. For electrochemical characterization by CV, electrodes on paper give a higher current response for ferri/ferrocyanide than transparency-based electrodes. When using ASV for the detection of heavy metals, the transparency-based device gave higher current response than paper-based device. Moreover, for the surface characterization using optical profilometry, carbon ink penetrated into the porous of filter paper but coated on the transparency film substrate affecting to surface roughness in transparency-based electrodes is higher than electrodes on paper. To improve the sensitivity of these devices, graphene (G) and polyaniline (PANI) nanocomposite was prepared by polymerization of aniline monomer in the presence of G and used for electrode modification. G/PANI nanocomposite-modified electrode was characterized by CV and used for heavy metals detection by ASV. This system will be very useful for portable environmental monitoring.

关键词： Graphene

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A powerless optical microsensor for monitoring intraocular pressure with keratoprostheses

A powerless optical microsensor for monitoring intraocular p...

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2013 17th International Conference on Solid-State Sensors, Actuators and Microsystems, TRANSDUCERS and EUROSENSORS 2013

作者： Ghannad-Rezaie, M. Gulari, M.N. De Melo Franco, R. Mian, S.I. Chronis, N. Department of Biomedical Engineering University of Michigan Ann Arbor United States Macromolecular Science and Engineering Program University of Michigan Ann Arbor United States Department of Ophthalmology and Visual Sciences University of Michigan Ann Arbor United States Department of Mechanical Engineering University of Michigan Ann Arbor United States

ISBN: (纸本)9781467359818

Frequent and accurate measurement of intraocular pressure (IOP) is required in monitoring patients who are at high risk of developing glaucoma. We present a novel electronic-free, wireless, optomechanical implantable IOP microsensor. The microsensor has a total volume of less than 1mm3 and is integrated into a keratoprosthesis (KPro). We performed ex-vivo experiments by implanting the microsensor/KPro assembly into human eyebank globes for two weeks. Our microsensor had 2 mmHg accuracy and less than 1 mmHg zero-drift. © 2013 IEEE.

关键词： Risk assessment

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A POWERLESS OPTICAL MICROSENSOR FOR MONITORING INTRAOCULAR PRESSURE WITH KERATOPROSTHESES

A POWERLESS OPTICAL MICROSENSOR FOR MONITORING INTRAOCULAR P...

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International Conference on Solid-State Sensors, Actuators and Microsystems

作者： M. Ghannad-Rezaie M. N. Gulari R. de Melo Franco S. I. Mian N. Chronis Department of Biomedical Engineering University of Michigan Macromolecular Science and Engineering Program University of Michigan Department of Ophthalmology and Visual Sciences University of Michigan

ISBN: (纸本)9781467359825

Frequent and accurate measurement of intraocular pressure (IOP) is required in monitoring patients who are at high risk of developing glaucoma. We present a novel electronic-free, wireless, optomechanical implantable IOP microsensor. The microsensor has a total volume of less than 1mm~3 and is integrated into a keratoprosthesis (KPro). We performed ex-vivo experiments by implanting the microsensor/KPro assembly into human eyebank globes for two weeks. Our microsensor had 2 mmHg accuracy and less than 1 mmHg zero-drift.

关键词： Wireless pressure sensor intraocular pressure implantable biocompatible near infrared

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Evidence of Positronium Bloch States in Porous Crystals of Zn4O-Coordination Polymers

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Physical Review Letters 2013年第19期110卷 197403-197403页

作者： Dhanadeep Dutta Jeremy I. Feldblyum David W. Gidley James Imirzian Ming Liu Adam J. Matzger Richard S. Vallery Antek G. Wong-Foy Department of Physics University of Michigan 450 Church Street Ann Arbor Michigan 48109 USA Department of Chemistry University of Michigan 930 North University Street Ann Arbor Michigan 48109 USA Macromolecular Science and Engineering University of Michigan 2300 Hayward Avenue Ann Arbor Michigan 48109-2136 USA NIST Polymers Division 100 Bureau Dr. M/S 8541 Gaithersburg Maryland 20899-8541 USA Nuclear Reactor Program Department of Nuclear Engineering North Carolina State University P.O. Box 7909 Raleigh North Carolina 27695 USA Department of Physics Grand Valley State University 151 Padnos Hall Allendale Michigan 49401 USA

Positronium (Ps) is shown to exist in a delocalized state in self-assembled metalorganic crystals that have large 1.3–1.5 nm cell sizes. Belonging to a class of materials with record high accessible specific surface areas, these highly porous crystals are the first to allow direct probing with simple annihilation lifetime techniques of the transport properties of long-lived triplet Ps in what is hypothesized to be a Bloch state. Delocalized Ps has unprecedented (high) Ps mobility driven primarily by weak phonon scattering with unusual and profound consequences on how Ps probes the lattice.

关键词： POSITRONIUM COORDINATION polymers ORGANOMETALLIC compounds ANNIHILATION reactions PHONONS -- Scattering

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Photoresponse Characteristics of Archetypal Metal-Organic Frameworks (vol 116, pg 3112, 2012)

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JOURNAL OF PHYSICAL CHEMISTRY C 2012年第15期116卷 8858-8858页

作者： Feldblyum, Jeremy I. Keenan, Elizabeth A. Matzger, Adam J. Maldonado, Stephen Macromolecular Science and Engineering University of Michigan Ann Arbor MI 48109-2136 2300 Hayward Avenue United States Department of Chemistry University of Michigan Ann Arbor MI 48109-1055 930 North University United States Program in Applied Physics University of Michigan Ann Arbor MI 48109-1040 450 Church Street United States

The photoelectrochemical responses of two archetypal metal–organic frameworks (MOFs), MOF-5 and MOF-177, have been assessed. Films of MOF-5 and MOF-177 were grown on carboxylic-acid-terminated conductive fluorine-doped tin oxide substrates. Separate analyses by powder X-ray diffraction, Raman spectroscopy, and fluorescence spectroscopy collectively indicated these films prepared via a solvothermal method in diethylformamide were free of residual impurities such as ZnO clusters and residual organics. Exposure of these films to white light illumination while immersed in acetonitrile electrolytes elicited measurable photocurrents. Wavelength-dependent analysis of the photoresponses showed that the measured photocurrents were induced by ultraviolet light and that the spectral response profiles followed closely the light absorption profiles of each respective material. Attenuation of the induced photocurrents was noted after prolonged ultraviolet light illumination and/or exposure of the films to H2O(l), indicating that the observed photoresponse properties are directly related to the structural integrity of these MOFs. The cumulative data illustrate that such MOFs have innately light-sensitive properties that are atypical in high surface area materials.

关键词： Photonics Photoresponse Metal organic frameworks Quantum mechanics Materials

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Structural Relaxations of Thin Polymer Films

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Physical Review Letters 2012年第26期108卷 268304-268304页

作者： Bradley Frieberg Emmanouil Glynos Peter F. Green Macromolecular Science and Engineering Program University of Michigan Ann Arbor Michigan 48109 USA Departments of Material Science and Engineering University of Michigan Ann Arbor Michigan 48109 USA Chemical Engineering University of Michigan Ann Arbor Michigan 48109 USA

Time-dependent changes of thermodynamic properties due to structural relaxations and physical aging occur in all glasses. We show that the physical aging of thin supported films of star-shaped macromolecules, with f arms of length Narm, exhibits average aging dynamics that are sensitive to f and Narm. Regions of the films in proximity to interfaces age at substantially different rates than the interior of the film; this is also true of linear chain systems. This behavior may be reconciled in terms of a universal picture that accounts only for changes in the local Tg of the films.

关键词： POLYMERS THIN films RELAXATION phenomena THERMODYNAMICS LINEAR systems STRUCTURAL dynamics

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