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Fatemeh Kiani, Negar Ashari Astani, Reza Rahighi, Ahmad Tayyebi, Meysam Tayebi, Jafar Khezri, Ehsan Hashemi, Ursula Rothlisberger, Abdolreza Simchi
In the present work, the effect of graphene oxide (GO) nanosheets on the antibacterial activity of CuO nanowire arrays under visible light irradiation is shown. A combined thermal oxidation/electrophoretic deposition technique was employed to prepare three-dimensional networks of graphene oxide nanosheets hybridized with vertically aligned CuO nanowires. With the help of standard antibacterial assays and X-ray photoelectron spectroscopy, it is shown that the light-activated antibacterial response of the hybrid material against gram-negative Escherichia coli is significantly improved as the oxide functional groups of the GO nanosheets are reduced...
March 7, 2018: Journal of Colloid and Interface Science
Giulia Avvisati, Claudia Cardoso, Daniele Varsano, Andrea Ferretti, Pierluigi Gargiani, Maria Grazia Betti
We report an advanced organic spin-interface architecture with magnetic remanence at room temperature, constituted by metal phthalocyanine molecules magnetically coupled with Co layer(s), mediated by graphene. Fe- and Cu-phthalocyanines assembled on graphene/Co have identical structural configurations, but FePc couples antiferromagnetically with Co, up to room temperature, while CuPc couples ferromagnetically, with weaker coupling and thermal stability, as deduced by element-selective X-ray magnetic circular dichroic signals...
March 20, 2018: Nano Letters
Chunxue Hao, Bochong Wang, Fusheng Wen, Congpu Mu, Jianyong Xiang, Lei Li, Zhongyuan Liu
Through a facile self-assembled process, an ultralight reduced graphene oxide/black phosphorus (rGO/BP) composite aerogel was successfully fabricated. The BP nanosheets were homogeneously distributed throughout the rGO 3D framework, and the interfaces between rGO and BP possessed four kinds of interconnections, such as wrapping, wearing, bridging and weak linking. As an ultralight composite, the rGO/BP aerogel could easily stand on the stamen of a flower. Compared with pure rGO aerogel, the rGO/BP composite aerogel exhibited enhanced microwave absorption ability...
March 20, 2018: Nanotechnology
Hao Li, Ming Li, Zhan Kang
The competition between the out-of-plane rigidity and the van der Waals interaction leads to the scrolled and folded structural configurations of graphene. These configuration changes, as compared with the initially planar geometry, significantly affect the electronic, optical and mechanical properties of graphene, promising exciting applications in graphene-nanoelectronics. We propose a finite-deformation theoretical model, in which no presumed assumptions on the geometries of deformed configurations are required...
March 20, 2018: Nanotechnology
Suji Gim, Hyung-Kyu Lim, Hyungjun Kim
The solid-liquid interface is of great interest because of its highly heterogeneous character and its ubiquity in various applications. The most fundamental physical variable determining the strength of the solid-liquid interface is the solid-liquid interfacial tension, which is usually measured according to the contact angle. However, an accurate experimental measurement and a reliable theoretical prediction of the contact angle remain lacking because of many practical issues. Here, we propose a first principles-based simulation approach to quantitatively predict the contact angle of an ideally clean surface using our recently developed multiscale simulation method of density functional theory in classical explicit solvents (DFT-CES)...
March 20, 2018: Journal of Physical Chemistry Letters
Peitao Xiao, Fanxing Bu, Ranran Zhao, Mohamed F Aly Aboud, Imran Shakir, Yuxi Xu
Synthesis of ultrasmall metal-organic frameworks (MOFs) nanoparticles has been widely recognized as a promising route to greatly enhance their properties but remains a considerable challenge. Herein, we report one facile and effective spatial-confined thermal pulverization strategy to successfully transform bulk Co-MOFs particles into sub-5 nm nanocrystals encapsulated within N-doped carbon/graphene (NC/G) by using conducting polymer coated Co-MOFs/graphene oxide as precursors. This strategy involves a feasible mechanism: calcination of Co-MOFs at proper temperature in air induces the partial thermal collapse/distortion of the framework, while the uniform coating of conducting polymer can significantly improve the decomposition temperature and maintain the component stability of Co-MOFs, thus leading to the pulverization of bulk Co-MOFs particles into ultrasmall nanocrystals without oxidation...
March 20, 2018: ACS Nano
Marek E Schmidt, Ahmed M M Hammam, Takuya Iwasaki, Teruhisa Kanzaki, Manoharan Muruganathan, Shinichi Ogawa, Hiroshi Mizuta
Carbon nanoscrolls (CNS) with their open ended morphology have recently attracted interest due to the potential application in gas capture, biosensors and interconnects. However, CNS currently suffer from the same issue that have hindered widespread integration of CNTs in sensors and devices: Formation is done ex-situ, and the tubes have to be placed with precision and reliability - a difficult task with low yield. Here, we demonstrate controlled in-situ formation of electrically contacted CNS from suspended graphene nanoribbons (GNRs) with slight tensile stress...
March 20, 2018: Nanotechnology
HongYing Mei, Wen Xu, Chao Wang, HaiFeng Yuan, Chao Zhang, Lan Ding, Jin Zhang, Chao Deng, YiFan Wang, Francois M Peeters
Magneto-optical (MO) properties of bi- and tri-layer graphene are investigated utilizing terahertz time-domain spectroscopy (THz TDS) in the presence of a strong magnetic fleld at room-temperature. In the Faraday conflguration and applying optical polarization measurements, we measure the real and imaginary parts of the longitudinal and transverse MO conductivities of difierent graphene samples. The obtained experimental data flt very well with the well-known MO Drude formula, from which we obtain key sample and material parameters of bi- and tri-layer graphene, such as the electron efiective mass, the
 electronic relaxation time and the electron density...
March 20, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Filippo Savazzi, Francesca Risplendi, Giuseppe Mallia, Nicholas M Harrison, Giancarlo Cicero
Graphene oxide (GO) is a versatile 2D material, whose properties can be tuned by changing the type and concentration of oxygen containing functional groups attached to its surface. However, a detailed knowledge of the dependence of the chemo/physical features of this material on its chemical composition is largely unknown. In this paper, we combine classical molecular dynamics and density functional theory simulations to predict the structural and electronic properties of GO at low degree of oxidation and suggest a revision of the Lerf-Klinowski model...
March 20, 2018: Journal of Physical Chemistry Letters
Sungsik Lee, Arokia Nathan, Jack Alexander-Webber, Philipp Braeuninger-Weimer, Abhay A Sagade, Haichang Lu, David Hasko, John Robertson, Stephan Hofmann
A positive shift in the Dirac point in graphene field-effect transistors was observed with Hall-effect measurements coupled with Kelvin-probe measurements at room temperature. This shift can be explained by the asymmetrical behavior of the contact resistance by virtue of the electron injection barrier at the source contact. As an outcome, an intrinsic resistance is given to allow a retrieval of an intrinsic carrier mobility found to be decreased with increasing gate bias, suggesting the dominance of short-range scattering in a single-layer graphene field-effect transistor...
March 21, 2018: ACS Applied Materials & Interfaces
Xiaoshuai Wu, Yan Qiao, Zhuanzhuan Shi, Wei Tang, Chang Ming Li
Interfacial electron transfer between electroactive biofilm and the electrode is crucial step for microbial fuel cells (MFCs) and other bioelectrochemical systems. Here, a hierarchically porous nitrogen-doped CNTs/reduced graphene oxide (rGO) composite with polyaniline as nitrogen source has been developed for MFCs anode. This composite possesses nitrogen atoms doped surface for improved flavin redox reaction and a three-dimensional (3D) hierarchically porous structure for rich bacterial biofilm growth. The N-CNTs/rGO anode delivers a maximum power density of 1137 mW m-2 in Shewanella putrefaciens CN32 microbial fuel cells, which is 8...
March 20, 2018: ACS Applied Materials & Interfaces
Shweta D Dabhi, Basant Roondhe, Prafulla K Jha
Understanding the interactions between biomolecules and boron nitride nanostructures is key for their use in nanobiotechnology and medical engineering. In this study, we investigated the adsorption of nucleobases adenine (A), guanine (G), cytosine (C), thymine (T) and uracil (U) over armchair and zigzag boron nitride nanoribbons (BNNR) using density functional theory to define the applicability of BNNR for the sensing of nucleobases and DNA sequencing. To appropriately account for dispersion, the van der Waals forces (DFT-D2)-type method developed by Grimme was also included in the calculations...
March 20, 2018: Physical Chemistry Chemical Physics: PCCP
Huda S AlSalem, Chloe Holroyd, Melissa Danial Iswan, Andrew B Horn, Melissa A Denecke, Sven P K Koehler
We report the unambiguous detection of phenyl groups covalently attached to functionalised graphene using non-linear spectroscopy. Sum-frequency generation was employed to probe graphene on a gold surface after chemical functionalisation using a benzene diazonium salt. We observe a distinct resonance at 3064 cm-1 which can clearly be assigned to an aromatic C-H stretch by comparison with a self-assembled monolayer on a gold substrate formed from benzenethiol. Not only does sum-frequency generation spectroscopy allow one to characterise functionalised graphene with higher sensitivity and much better specificity than many other spectroscopic techniques, but it also opens up the possibility to assess the coverage of graphene with functional groups, and to determine their orientation relative to the graphene surface...
March 20, 2018: Physical Chemistry Chemical Physics: PCCP
Martin Konečný, Miroslav Bartosik, Jindrich Mach, Vojtěch Švarc, David Nezval, Jakub Piastek, Pavel Procházka, Aleš Cahlík, Tomas Sikola
The article shows how the dynamic mapping of surface potential (SP) measured by Kelvin Probe Force Microscopy in combination with a calculation of diffusion-like equation and the theory based on the Brunauer-Emmett-Teller (BET) model of water condensation and electron hopping can provide the information concerning the resistivity of low conductive surfaces and their water coverage. This is enabled by a study of charge transport between isolated and grounded graphene sheets on a silicon dioxide surface at different relative humidity (RH) with regard to the use of graphene in ambient electronic circuits, and especially in sensors...
March 20, 2018: ACS Applied Materials & Interfaces
Dunia E Santiago, Luisa M Pastrana-Martínez, Elisenda Pulido-Melián, Javier Araña, Joaquim L Faria, Adrián M T Silva, Óscar González-Díaz, José M Doña-Rodríguez
Magnetite (Fe3 O4 ), a core-shell material (SiO2 @Fe3 O4 ), and reduced graphene oxide-Fe3 O4 (referred as rGO-MN) were used as supports of a specific highly active TiO2 photocatalyst. Thermal treatments at 200 or 450 °C, different atmospheres (air or N2 ), and TiO2 :support weight ratios (1.0, 1.5, or 2.0) were investigated. X-ray diffractograms revealed that magnetite is not oxidized to hematite when the core-shell SiO2 @Fe3 O4 material-or a N2 atmosphere (instead of air) in the thermal treatment-was employed to prepare the TiO2 -based catalysts (the magnetic properties being preserved)...
March 2, 2018: Environmental Science and Pollution Research International
Shiho Kobayashi, Yuki Anno, Kuniharu Takei, Takayuki Arie, Seiji Akita
Graphene/semiconductor Schottky junctions are an emerging field for high-performance optoelectronic devices. This study investigates not only the steady state but also the transient photoresponse of graphene field-effect transistor (G-FET) of which gate bias is applied through the Schottky barrier formed at an n-type Si/graphene interface with a thin oxide layer, where the oxide thickness is sufficiently thin for tunneling of the charge carrier. To analyze the photoresponse, we formulate the charge accumulation process at the n-Si/graphene interface, where the tunneling process through the SiOx layer to graphene occurs along with recombination of the accumulated holes and the electrons in the graphene at the surface states on the SiOx layer...
March 19, 2018: Scientific Reports
Xiang Yu, Zhen Zhang, Fei Liu, Yi Ren
Direct growth of spherical graphene with large surface area is important for various applications in sensor technology. However, the preparation of transfer-free graphene on different substrates is still a challenge. This study presents a novel approach for the transfer-free graphene growth directly on cemented carbide. The used simple thermal annealing induces an in-situ transformation of magnetron-sputtered amorphous silicon carbide films into the graphene matrix. The study reveals the role of Co, a binding phase in cemented carbides, in Si sublimation process, and its interplay with the annealing temperature in development of the graphene matrix...
March 19, 2018: Scientific Reports
Andreas Mittelberger, Christian Kramberger, Jannik C Meyer
Atomically resolved images of monolayer organic crystals have only been obtained with scanning probe methods so far. On the one hand, they are usually prepared on surfaces of bulk materials, which are not accessible by (scanning) transmission electron microscopy. On the other hand, the critical electron dose of a monolayer organic crystal is orders of magnitudes lower than the one for bulk crystals, making (scanning) transmission electron microscopy characterization very challenging. In this work we present an atomically resolved study on the dynamics of a monolayer CuPcCl16 crystal under the electron beam as well as an image of the undamaged molecules obtained by low-dose electron microscopy...
March 19, 2018: Scientific Reports
Nils M Freitag, Tobias Reisch, Larisa A Chizhova, Péter Nemes-Incze, Christian Holl, Colin R Woods, Roman V Gorbachev, Yang Cao, Andre K Geim, Kostya S Novoselov, Joachim Burgdörfer, Florian Libisch, Markus Morgenstern
Coherent manipulation of the binary degrees of freedom is at the heart of modern quantum technologies. Graphene offers two binary degrees: the electron spin and the valley. Efficient spin control has been demonstrated in many solid-state systems, whereas exploitation of the valley has only recently been started, albeit without control at the single-electron level. Here, we show that van der Waals stacking of graphene onto hexagonal boron nitride offers a natural platform for valley control. We use a graphene quantum dot induced by the tip of a scanning tunnelling microscope and demonstrate valley splitting that is tunable from -5 to +10 meV (including valley inversion) by sub-10-nm displacements of the quantum dot position...
March 19, 2018: Nature Nanotechnology
Mahroo Khaleghi, Khadijeh Didehban, Meisam Shabanian
Melamine terephthaldehyde modified graphene oxide (MTR-GO) with optimum content was easily prepared via ultrasonication method and used as anti-corrosion additive for Poly (vinyl chloride) (PVC). The effects of ultrasonicated MTR-GO on the mechanical, chemical and thermal resistance of the PVC were thoroughly studied. Change percentage of tensile strength and weight change percentage of PVC (P) and PVC/MTR-GO nanocomposite (PN) in acetone and sodium hypochlorite (NaClO) media at two different exposure temperature (20 °C and 50 °C) were examined...
May 2018: Ultrasonics Sonochemistry
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