639 results match your criteria free-standing graphene

Epitaxy, exfoliation, and strain-induced magnetism in rippled Heusler membranes.

Nat Commun 2021 May 3;12(1):2494. Epub 2021 May 3.

Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA.

Single-crystalline membranes of functional materials enable the tuning of properties via extreme strain states; however, conventional routes for producing membranes require the use of sacrificial layers and chemical etchants, which can both damage the membrane and limit the ability to make them ultrathin. Here we demonstrate the epitaxial growth of the cubic Heusler compound GdPtSb on graphene-terminated AlO substrates. Despite the presence of the graphene interlayer, the Heusler films have epitaxial registry to the underlying sapphire, as revealed by x-ray diffraction, reflection high energy electron diffraction, and transmission electron microscopy. Read More

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Drying-Time Study in Graphene Oxide.

Nanomaterials (Basel) 2021 Apr 19;11(4). Epub 2021 Apr 19.

CompNano, School of Physical Sciences and Nanotechnology, Yachay Tech University, Urcuquí EC-100119, Ecuador.

Graphene oxide (GO) exhibits different properties from those found in free-standing graphene, which mainly depend on the type of defects induced by the preparation method and post-processing. Although defects in graphene oxide are widely studied, we report the effect of drying time in GO and how this modifies the presence or absence of edge-, basal-, and sp-type defects. The effect of drying time is evaluated by Raman spectroscopy, UV-visible spectroscopy, and transmission electron microscopy (TEM). Read More

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Graphene Buffer Layer on SiC as a Release Layer for High-Quality Freestanding Semiconductor Membranes.

Nano Lett 2021 Apr 26. Epub 2021 Apr 26.

Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.

Free-standing crystalline membranes are highly desirable owing to recent developments in heterogeneous integration of dissimilar materials. Van der Waals (vdW) epitaxy enables the release of crystalline membranes from their substrates. However, suppressed nucleation density due to low surface energy has been a challenge for crystallization; reactive materials synthesis environments can induce detrimental damage to vdW surfaces, often leading to failures in membrane release. Read More

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Mechanical strength and flexibility in [Formula: see text]-4H borophene.

Sci Rep 2021 Apr 6;11(1):7547. Epub 2021 Apr 6.

Computational Nanophysics Laboratory (CNL), Department of Physics, University of Guilan, P. O. Box 41335-1914, Rasht, Iran.

Very recently, a novel phase of hydrogenated borophene, namely [Formula: see text]-4H, has been synthesized in a free-standing form. Unlike pure borophenes, this phase shows very good stability in the air environment and possesses semiconducting characteristics. Because of the interesting stiffness and flexibility of borophenes, herein, we systematically studied the mechanical properties of this novel hydrogenated phase. Read More

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Pyridinic-Type N-Doped Graphene on Cobalt Substrate as Efficient Electrocatalyst for Oxygen Reduction Reaction in Acidic Solution in Fuel Cell.

J Phys Chem Lett 2021 Apr 5;12(14):3552-3559. Epub 2021 Apr 5.

Center for Environmental Science, College of Natural and Computational Sciences, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia.

In this study, we use density functional theory to investigate the catalytic activity of graphene (G), single vacancy defective graphene (G), quaternary N-doped graphene (NG), and pyridinic N-doped graphene (NG, 3NG, and 4NG) on Co(0001) substrate for an oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). The results show pyridinic N-doped graphene on a Co support exhibited better performance than the NG on a Co support and free-standing systems. According to the results, ORR intermediates (*OOH, *O, and *OH) become more stable due to the presence of a Co substrate. Read More

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On the Reactivity Enhancement of Graphene by Metallic Substrates towards Aryl Nitrene Cycloadditions.

Chemistry 2021 Mar 28. Epub 2021 Mar 28.

Chemistry Department, University of Massachusetts Lowell, One University Ave, Lowell, MA 01854, USA.

Pristine graphene is fairly inert chemically, and as such, most application-driven studies use graphene oxide, or reduced graphene oxide. Using substrates to modulate the reactivity of graphene represents a unique strategy in the covalent functionalization of this otherwise fairly inert material. It was found that the reactivity of pristine graphene towards perfluorophenyl azide (PFPA) can be enhanced by a metal substrate on which graphene is supported. Read More

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All Si N Nanowires Membrane Based High-Performance Flexible Solid-State Asymmetric Supercapacitor.

Small 2021 May 24;17(18):e2008056. Epub 2021 Mar 24.

State Key Laboratory of Solidification Processing, Shaanxi Province Key Laboratory of Fiber Reinforced Light Composite Materials, Carbon/Carbon Composites Research Center, Northwestern Polytechnical University, Xi'an, 710072, China.

Recently, much attention has been drawn in the development of flexible energy storage devices due to the increasing demands for flexible/portable electronic devices with high energy density, low weight, and good flexibility. Herein, vertically oriented graphene nanosheets (VGNs) are in situ fabricated on the surface of free-standing and flexible Si N nanowires (NWs) membrane by plasma-enhanced chemical vapor deposition (PECVD), which are directly used as flexible nanoscale conductive substrates. NiCo O hollow nanospheres (HSs) and FeOOH amorphous nanorods (NRs) are finally prepared on Si N @VGNs, which are served as the positive and negative electrodes, respectively. Read More

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Self-assembled graphene-based microfibers with eclectic optical properties.

Sci Rep 2021 Mar 9;11(1):5451. Epub 2021 Mar 9.

Faculty of Chemistry, Bu-Ali Sina University, Hamedan, 6517838695, Iran.

The construction of graphene-based microfibers with reinforced mechanical and electrical properties has been the subject of numerous researches in recent years. However, the fabrication of graphene-based fibers with remarkable optical features still remains a challenge and has not been addressed so far. This paper aims to report a series of flexible self-assembled fibers, synthesized through a few-minute sonication of thermally oxidized graphene oxide nanosheets, so-called Nanoporous Over-Oxidized Graphene (NOG), in an acidic medium. Read More

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Free-standing electrochemically coated MoS based 3D-printed nanocarbon electrode for solid-state supercapacitor application.

Nanoscale 2021 Mar 16;13(11):5744-5756. Epub 2021 Mar 16.

Future Energy and Innovation Laboratory, Central European Institute of Technology, Brno University of Technology, Purkyňova 123, 61200 Brno, Czech Republic.

The 3D-printing technology offers an innovative approach to develop energy storage devices because of its ability to create facile and low cost customized electrodes for modern electronics. Among the recently explored 2D nanomaterials beyond graphene, molybdenum sulfide (MoS) has been found as a promising material for electrochemical energy storage devices. In this study, a nanocarbon-based conductive filament was 3D-printed and then activated by solvent treatment, followed by electrodeposition of MoS on the printed nanocarbon electrode's surface. Read More

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Quasi-static 3D structure of graphene ripple measured using aberration-corrected TEM.

Nanoscale 2021 Mar 15;13(11):5847-5856. Epub 2021 Mar 15.

Division of Applied Physics, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan.

Free-standing graphene has a three-dimensional (3D) structure, called a ripple, rather than a perfect two-dimensional (2D) crystal. Since theoretical calculations suggest that a ripple strongly influences various fundamental physicochemical properties of graphene, it is important to clarify the ripple structure quantitatively in experiments. This paper proposes a new method of measuring the 3D atomic structure of a ripple by using aberration-corrected transmission electron microscopy (TEM). Read More

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Mechanics of penta-graphene with vacancy defects under large amplitude tensile and shear loading.

Nanotechnology 2021 Apr 14;32(27). Epub 2021 Apr 14.

Faculty of Civil Engineering and Mechanics, Jiangsu University, No. 301 Xuefu Road, Zhenjiang, Jiangsu 210013, People's Republic of China.

Penta-graphene is a new two-dimensional metastable carbon allotrope composed entirely of carbon pentagons with unique electronic and mechanical properties. In this work we evaluate the mechanical properties of new classes of defective penta-graphene (DPG) subjected to tensile and shear loading by using molecular dynamics simulations. The types of defects considered here are monovacancy at either 4-coordinated C1 site or 3-coordinated C2 site, and double vacancy (DV). Read More

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Conversion of Amorphous Carbon on Silicon Nanostructures into Similar Shaped Semi-Crystalline Graphene Sheets.

J Nanosci Nanotechnol 2021 Sep;21(9):4949-4954

International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, 305-0044, Japan.

Graphene sheets displaying partial crystallinity and nanowire structures were formed on a silicon substrate with silicon nanowires by utilizing an amorphous carbon source. The carbon source was deposited onto the silicon nanostructured substrate by breaking down a polymer precursor and was crystallized by a nickel catalyst during relatively low temperature inert gas annealing. The resulting free-standing graphene-based material can remain on the substrate surface after catalyst removal or can be removed as a separate film. Read More

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September 2021

Colloidal Nanostructures of Transition-Metal Dichalcogenides.

Acc Chem Res 2021 Mar 4;54(6):1517-1527. Epub 2021 Mar 4.

ConspectusLayered transition-metal dichalcogenides (TMDs) are intriguing two-dimensional (2D) compounds where metal and chalcogen atoms are covalently bonded in each monolayer, and the monolayers are held together by weak van der Waals forces. Distinct from graphene, which is chemically inert, layered TMDs exhibit a wide range of electronic, optical, catalytic, and magnetic properties dependent upon their compositions, crystal structures, and thicknesses, which make them fundamentally and technologically important. TMD nanostructures are traditionally synthesized using gas-phase chemical deposition methods, which are typically limited to small-scale samples of substrate-bound planar materials. Read More

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Metallated Graphynes as a New Class of Photofunctional 2D Organometallic Nanosheets.

Angew Chem Int Ed Engl 2021 May 7;60(20):11326-11334. Epub 2021 Apr 7.

Department of Applied Biology and Chemical Technology and Research Institute for Smart Energy, The Hong Kong Polytechnic University (PolyU), Hung Hom, Hong Kong, P. R. China.

Two-dimensional (2D) nanomaterials are attracting much attention due to their excellent electronic and optical properties. Here, we report the first experimental preparation of two free-standing mercurated graphyne nanosheets via the interface-assisted bottom-up method, which integrates both the advantages of metal center and graphyne. The continuous large-area nanosheets derived from the chemical growth show the layered molecular structural arrangement, controllable thickness and enhanced π-conjugation, which result in their stable and outstanding broadband nonlinear saturable absorption (SA) properties (at both 532 and 1064 nm). Read More

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A reactive molecular dynamics study on the mechanical properties of a recently synthesized amorphous carbon monolayer converted into a nanotube/nanoscroll.

Phys Chem Chem Phys 2021 Apr;23(15):9089-9095

Institute of Physics, University of Brasília, Brasília 70919-970, Brazil.

Recently, laser-assisted chemical vapor deposition has been used to synthesize a free-standing, continuous, and stable monolayer amorphous carbon (MAC). MAC is a pure carbon structure composed of randomly distributed five, six, seven, and eight atom rings, which is different from that of disordered graphene. More recently, amorphous MAC-based nanotubes (a-CNT) and nanoscrolls (a-CNS) were proposed. Read More

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A Fishing-Net-Like 3D Host for Robust and Ultrahigh-Rate Lithium Metal Anodes.

Small 2021 Mar 23;17(11):e2007231. Epub 2021 Feb 23.

State Key Laboratory of Control and Simulation of Power System and Generation Equipments, Tsinghua University, Beijing, 100084, China.

Constructing an architectural host is demonstrated to be an effective strategy for long-life lithium metal anodes (LMAs). Herein, an integrated 3D host for stable and ultrahigh-rate LMAs is developed by a binary highly conductive network of 2D reduced graphene oxide (rGO) and 1D carbon nanofibers (CNF) anchored with 0D ultrasmall MgZnO nanoparticles (MgZnO/CNF-rGO). A facile net-fishing strategy is proposed to combine the rGO nanosheets with free-standing CNF matrix as interconnected paths for fast electron transport. Read More

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Hierarchical N,P co-doped graphene aerogels framework assembling vertically grown CoMn-LDH nanosheets as efficient bifunctional electrocatalyst for rechargeable Zinc-air battery.

J Colloid Interface Sci 2021 May 1;590:476-486. Epub 2021 Feb 1.

Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Linggong road 2#, Dalian 116024, China.

Exploiting the low-cost and high-efficiency bifunctional oxygen electrocatalysts to substitute platinum-group metals is highly desirable but challenging for energy storage/conversion technologies. Herein, we develop a combined gelation/self-assemble/freeze drying process to fabricate a free-standing porous architectures through vertical anchoring two-dimensional (2D) CoMn-LDH nanosheets on three-dimensional (3D) hierarchical N,P co-doped graphene aerogels (NPGA) framework. This unique configuration endows CoMn-LDH/NPGA outstanding catalytic activity toward both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with a potential difference of ca. Read More

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Observation of chiral edge states in gapped nanomechanical graphene.

Sci Adv 2021 Jan 6;7(2). Epub 2021 Jan 6.

Department of Electronic Engineering, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong.

Emerging in diverse areas of physics, edge states have been exploited as an efficient strategy of manipulating electrons, photons, and phonons for next-generation hybrid electro-optomechanical circuits. Among various edge states, gapless chiral edge states harnessing quantum spin/valley Hall effects in graphene or graphene-like materials are especially unique. Here, we report on an experimental demonstration of chiral edge states in gapped "nanomechanical graphene"-a honeycomb lattice of free-standing silicon nitride nanomechanical membranes with broken spatial inversion symmetry. Read More

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January 2021

Complementary LEEM and eV-TEM for imaging and spectroscopy.

Ultramicroscopy 2021 Mar 7;222:113199. Epub 2021 Jan 7.

Huygens-Kamerlingh Onnes Laboratory, Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, Leiden, The Netherlands.

Transmission electron microscopy at very low energy is a promising way to avoid damaging delicate biological samples with the incident electrons, a known problem in conventional transmission electron microscopy. For imaging in the 0-30 eV range, we added a second electron source to a low energy electron microscopy (LEEM) setup, enabling imaging and spectroscopy in both transmission and reflection mode at nanometer (nm) resolution. The latter is experimentally demonstrated for free-standing graphene. Read More

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Mechanics of free-standing inorganic and molecular 2D materials.

Nanoscale 2021 Jan;13(3):1443-1484

Physics of Supramolecular Systems and Surfaces, Bielefeld University, 33615 Bielefeld, Germany.

The discovery of graphene has triggered a great interest in inorganic as well as molecular two-dimensional (2D) materials. In this review, we summarize recent progress in the mechanical characterization of free-standing 2D materials, such as graphene, hexagonal boron nitride (hBN), transition metal-dichalcogenides, MXenes, black phosphor, carbon nanomembranes (CNMs), 2D polymers, 2D metal organic frameworks (MOFs) and covalent organic frameworks (COFs). Elastic, fracture, bending and interfacial properties of these materials have been determined using a variety of experimental techniques including atomic force microscopy based nanoindentation, in situ tensile/fracture testing, bulge testing, Raman spectroscopy, Brillouin light scattering and buckling-based metrology. Read More

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January 2021

Deuterium Adsorption on Free-Standing Graphene.

Nanomaterials (Basel) 2021 Jan 8;11(1). Epub 2021 Jan 8.

Dipartimento di Fisica and INFN Sezione di Roma 1, Sapienza Università di Roma, P.le Aldo Moro 2, 00185 Rome, Italy.

A suitable way to modify the electronic properties of graphene-while maintaining the exceptional properties associated with its two-dimensional (2D) nature-is its functionalisation. In particular, the incorporation of hydrogen isotopes in graphene is expected to modify its electronic properties leading to an energy gap opening, thereby rendering graphene promising for a widespread of applications. Hence, deuterium (D) adsorption on free-standing graphene was obtained by high-energy electron ionisation of D2 and ion irradiation of a nanoporous graphene (NPG) sample. Read More

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January 2021

In Situ Growth of Oriented Polyaniline Nanorod Arrays on the Graphite Flake for High-Performance Supercapacitors.

ACS Omega 2020 Dec 8;5(50):32395-32402. Epub 2020 Dec 8.

Fine Chemical Industry Research Institute, School of Chemistry, Sun Yat-sen University, Guangzhou 510275, Guangdong, China.

Polyaniline with oriented nanorod arrays could provide high surface area and relaxed nanostructure to optimize ion diffusion paths, thus enhancing the performance of the device. In this paper, we designed an all-solid symmetrical supercapacitor with good performance based on polyaniline nanorod arrays in situ-grown on a graphite flake free-standing substrate. The specific capacitance, cycle stability, and energy density of the prepared supercapacitor device were 135 F/g, 75. Read More

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December 2020

Fracture and Fatigue of AlO-Graphene Nanolayers.

Nano Lett 2021 01 29;21(1):437-444. Epub 2020 Dec 29.

Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Canada M5S 3G8.

AlO-graphene nanolayers are widely used within integrated micro/nanoelectronic systems; however, their lifetimes are largely limited by fracture both statically and dynamically. Here, we present a static and fatigue study of thin (1-11 nm) free-standing AlO-graphene nanolayers. A remarkable fatigue life of greater than one billion cycles was obtained for films <2. Read More

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January 2021

An Ultra-Long-Life Flexible Lithium-Sulfur Battery with Lithium Cloth Anode and Polysulfone-Functionalized Separator.

ACS Nano 2021 Jan 28;15(1):1358-1369. Epub 2020 Dec 28.

Institute for Frontier Materials, Deakin University, 75 Pigdons Road, Waurn Ponds, VIC 3216, Australia.

Flexible and high-performance batteries are urgently required for powering flexible/wearable electronics. Lithium-sulfur batteries with a very high energy density are a promising candidate for high-energy-density flexible power source. Here, we report flexible lithium-sulfur full cells consisting of ultrastable lithium cloth anodes, polysulfone-functionalized separators, and free-standing sulfur/graphene/boron nitride nanosheet cathodes. Read More

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January 2021

Hierarchical NiCoSe nanoneedles/nanosheets with N-doped 3D porous graphene architecture as free-standing anode for superior sodium ion batteries.

J Colloid Interface Sci 2021 Apr 9;587:260-270. Epub 2020 Dec 9.

Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China. Electronic address:

In order to cope with the problem of insufficient lithium metal reserves, sodium ion batteries (SIBs) are proposed and extensively studied for the next-generation batteries. In our work, hierarchical NiCoSe nanoneedles/nanosheets are deposited on the skeleton of N-doped three dimensional porous graphene (NPG) by a convenient solvothermal method and subsequent gas-phase selenization process. Compared with NiCoSe powder, the optimized NiCoSe/N-doped porous graphene composite (denoted as NCS@NPG) as self-supporting anode exhibits the excellent electrode activity for SIBs, with a specific capacity of 500 mAh/g and 257 mAh/g at a current density of 0. Read More

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Mechanochemical Formation of Protein Nanofibril: Graphene Nanoplatelet Hybrids and Their Thermoelectric Properties.

ACS Sustain Chem Eng 2020 Nov 17;8(47):17368-17378. Epub 2020 Nov 17.

Electronic and Photonic Materials Division, Biomolecular and Organic Electronics, Department of Physics, Chemistry, and Biology, Linköping University, Linköping 581 83, Sweden.

Hybrids between biopolymeric materials and low-cost conductive carbon-based materials are interesting materials for applications in electronics, potentially reducing the need for materials that generate environmentally harmful electronic waste. Herein we investigate a scalable ball-milling method to form graphene nanoplatelets (GNPs) by milling graphite flakes with aqueous dispersions of proteins or protein nanofibrils (PNFs). Aqueous GNP dispersions with high concentrations (up to 3. Read More

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November 2020

Printable Free-Standing Hybrid Graphene/Dry-Spun Carbon Nanotube Films as Multifunctional Electrodes for Highly Stable Perovskite Solar Cells.

ACS Appl Mater Interfaces 2020 Dec 20;12(49):54806-54814. Epub 2020 Nov 20.

Department of Nano Fusion Technology, Pusan National University, Busandaehak-ro 63beon-gil 2, Geumjeong-gu, Busan 46241, Republic of Korea.

Perovskite solar cells (PSCs) have attracted immense attention owing to their outstanding power conversion efficiency (PCE). However, their counter electrodes are commonly produced by evaporating metals, such as Ag and Au, under high vacuum conditions, which make the PSCs costly, thereby limiting their large-scale production. In this study, a free-standing hybrid graphene/carbon nanotube film was carefully designed to replace noble metal PSC counter electrodes to reduce the cost and increase the stability of PSCs. Read More

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December 2020

Free-Standing Graphene Oxide and Carbon Nanotube Hybrid Papers with Enhanced Electrical and Mechanical Performance and Their Synergy in Polymer Laminates.

Int J Mol Sci 2020 Nov 14;21(22). Epub 2020 Nov 14.

Laboratory of Bio-Inspired, Bionic, Nano, Meta Materials & Mechanics, Department of Civil, Environmental and Mechanical Engineering, University of Trento, via Mesiano 77, 38123 Trento, Italy.

Hybrid nanomaterials fabricated by the heterogeneous integration of 1D (carbon nanotubes) and 2D (graphene oxide) nanomaterials showed synergy in electrical and mechanical properties. Here, we reported the infiltration of carboxylic functionalized single-walled carbon nanotubes (C-SWNT) into free-standing graphene oxide (GO) paper for better electrical and mechanical properties than native GO. The stacking arrangement of GO sheets and its alteration in the presence of C-SWNT were comprehensively explored through scanning electron microscopy, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction. Read More

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November 2020

The electron-phonon coupling constant for single-layer graphene on metal substrates determined from He atom scattering.

Phys Chem Chem Phys 2021 Apr 12;23(13):7575-7585. Epub 2020 Nov 12.

Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal, 4, 20018 Donostia-San Sebastián, Spain.

Recent theory has demonstrated that the value of the electron-phonon coupling strength λ can be extracted directly from the thermal attenuation (Debye-Waller factor) of helium atom scattering reflectivity. This theory is here extended to multivalley semimetal systems and applied to the case of graphene on different metal substrates and graphite. It is shown that λ rapidly increases for decreasing graphene-substrate binding strength. Read More

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Bioproduced Polymers Self-Assemble with Graphene Oxide into Nanocomposite Films with Enhanced Mechanical Performance.

ACS Nano 2020 11 4;14(11):14731-14739. Epub 2020 Nov 4.

Department of Bionanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands.

Graphene oxide (GO) has recently been highlighted as a promising multipurpose two-dimensional material. However, free-standing graphene oxide films suffer from poor strength and flexibility, which limits scaling-up of production and lifetime structural robustness in applications. Inspired by the relationship between the organic and inorganic components of the hierarchical structure of nacre found in mollusk shells, we have fabricated self-assembled, layered graphene-based composite films. Read More

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November 2020