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4 páginas, 4 figuras.-- PACS number(s): 81.05.ue, 62.25.−g, 72.80.Vp.-- et al. ; We report a theoretical study suggesting a novel type of electronic switching effect, driven by the geometrical reconstruction of nanoscale graphene-based junctions. We considered junction structures that have alternative metastable configurations transformed by rotations of local carbon dimers. The use of external mechanical strain allows a control of the energy-barrier heights of the potential profiles and also changes the reaction character from endothermic to exothermic or vice versa. The reshaping of the atomic details of the junction encode binary electronic "on" or "off" states, with on/off transmission ratio that can reach up to 104–105. Our results suggest the possibility to design modern logical switching devices or mechanophore sensors, monitored by mechanical strain and structural rearrangements. ; This work was partially funded by the Alexander vonHumboldt Foundation, the European Union, the Free State of Saxony (SAB Project No. A2-13996/2379), the NANOSIM-GRAPHENE (Project No. ANR-09-NANO-016- 01), and the South Korean Ministry of Education, Science, and Technology Program (WCU ITCE Project No. R31-2008- 000-10100-0). ; Peer reviewed

4 páginas, 4 figuras.-- PACS number(s): 61.46.Km, 73.63.−b, 62.25.−g.-- et al. ; The electrical response of graphene-based materials can be tailored under mechanical stress. We report different switching behaviors that take place in mechanically deformed graphene nanoribbons prior to the breakage of the junction. By performing tight-binding molecular dynamics, the study of structural changes of graphene nanoribbons with different widths is achieved, revealing that carbon chains are the ultimate bridges before the junction breaks. The electronic and transport calculations show that binary on/off states can be switched prior to and during breakage depending on the atomic details of the nanoribbon. This work supports the interpretation of recent experiments on nonvolatile memory element engineering based on graphene break junctions. ; This work is supported by the European Union and the Freistaat Sachsen (Project No. 13857/2379), the NANOSIM-GRAPHENE Project (ANR-09-NANO-016- 01) of ANR/P3N2009, and the Alexander von Humboldt Foundation. ; Peer reviewed

WOS: 000314706300003 ; PubMed ID: 23390578 ; We propose a hybrid nano-structuring scheme for tailoring thermal and thermoelectric transport properties of graphene nanoribbons. Geometrical structuring and isotope cluster engineering are the elements that constitute the proposed scheme. Using first-principles based force constants and Hamiltonians, we show that the thermal conductance of graphene nanoribbons can be reduced by 98.8% at room temperature and the thermoelectric figure of merit, ZT, can be as high as 3.25 at T = 800 K. The proposed scheme relies on a recently developed bottom-up fabrication method, which is proven to be feasible for synthesizing graphene nanoribbons with an atomic precision. ; German Research Foundation (DFG) [SPP-1386, CU44/11-1]; German Excellence Initiative via the Cluster of Excellence "Center for Advancing Electronics Dresden" (cfAED) [EXC 1056]; European Union (ERDF); Free State of Saxony via TP A2 ("MolFunc"/"MolDiagnosik") of the Cluster of Excellence "European Center for Emerging Materials and Processes Dresden" (ECEMP); Danish Council for Independent Research (DFF); NSF [DMR 0844082]; Scientific and Technological Research Council of Turkey (TUBITAK); Ministry of Education, Science and Technology through the National Research Foundation of Korea [R31-10100] ; We would like to acknowledge the support by the priority program Nanostructured Thermoelectrics (SPP-1386) of the German Research Foundation (DFG) (Contract No. CU44/11-1), the German Excellence Initiative via the Cluster of Excellence EXC 1056 "Center for Advancing Electronics Dresden" (cfAED), the European Union (ERDF) and the Free State of Saxony via TP A2 ("MolFunc"/"MolDiagnosik") of the Cluster of Excellence "European Center for Emerging Materials and Processes Dresden" (ECEMP). H. S. acknowledges funding from the Danish Council for Independent Research (DFF). C. S. and T. C. acknowledge support from NSF (DMR 0844082) to International Institute of Materials for Energy Conversion at Texas A&M University. The parts of computations are carried out at the facilities of Laboratory of Computational Engineering of Nanomaterials also supported by ARO, ONR, and DOE grants. We also would like to thank for generous time allocation made for this project by the Supercomputing Center of Texas A&M University. C. S. acknowledges the support from The Scientific and Technological Research Council of Turkey (TUBITAK) to his research at Anadolu University. G. C. further acknowledges the World Class University program funded by the Ministry of Education, Science and Technology through the National Research Foundation of Korea (R31-10100). The Center for Information Services and High Performance Computing (ZIH) at the TU-Dresden is also acknowledged.

Quantum interference (QI) phenomena between electronic states in molecular circuits offer a new opportunity to design new types of molecular devices such as molecular sensors, interferometers, and thermoelectric devices. Controlling the QI effect is a key challenge for such applications. For the development of single molecular devices employing QI effects, a systematic study of the relationship between electronic structure and the quantum interference is needed. In order to uncover the essential topological requirements for the appearance of QI effects and the relationship between the QI-affected line shape of the transmission spectra and the electronic structures, we consider a homogeneous toy model where all on-site energies are identical and model four types of molecular junctions due to their topological connectivities. We systematically analyze their transmission spectra, density of states, and thermoelectric properties. Even without the degree of freedom for on-site energies an asymmetric Fano peak could be realized in the homogeneous systems with the cyclic configuration. We also calculate the thermoelectric properties of the model systems with and without fluctuation of on-site energies. Even under the fluctuation of the on-site energies, the finite thermoelectrics are preserved for the Fano resonance, thus cyclic configuration is promising for thermoelectric applications. This result also suggests the possibility to detect the cyclic configuration in the homogeneous systems and the presence of the QI features from thermoelectric measurements. ; European project Synaptic Molecular Networks for Bioinspired Information Processing (SYMONE) (318597); German Research Foundation (DFG); European Union; The Science Academy, Turkey; TUBITAK-BIDEB (113C032); TUBITAK-ULAKBIM High Performance and Grid Computing Center (TRUBA Resources); EU (318516)

Emerging pollutants are an essential class of recalcitrant contaminants that are not eliminated from water after conventional treatment. Here, a photocatalytic microporous membrane based on polyvinylidene difluoride-co-trifluoroethylene (PVDF−TrFE) with immobilised TiO2 nanoparticles, prepared by solvent casting, was tested against representative emerging pollutants. The structure and composition of these polymeric membranes were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, porosimetry, and contact angle goniometry. The nanocomposites exhibited a porous structure with a uniform distribution of TiO2 nanoparticles. The addition of TiO2 did not change the structure of the polymeric matrix; however, it increased the wettability of the nanocomposite. The nanocomposites degraded 99% of methylene blue (MB), 95% of ciprofloxacin (CIP), and 48% of ibuprofen (IBP). The microporous nanocomposite exhibited no photocatalytic efficiency loss after four use cycles, corresponding to 20 h of UV irradiation. The reusability of this system confirms the promising nature of polymer nanocomposites as the basis for cost-effective and scalable treatments of emerging pollutants. ; P.M. Martins thanks the FCT for the grant SFRH/BD/98616/2013. The authors acknowledge funding from the Basque Government Industry Department under the ELKARTEK Program and the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) (including the FEDER financial support). This work was also supported by the Graduate Academy of the Technische Universität Dresden. ; M.; visualization, J.M.R.; supervision, G.C., S.L.-M. Funding: This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the strategic project UID/FIS/04650/2013 by FEDER funds through the COMPETE 2020–Programa Operacional Competitividade e Internacionalização (POCI) with the reference project ...

This article is part of the themed collection: Recent Open Access Articles. ; We present the chemical anchoring of a DMBI-P molecule-rotor to the Au(111) surface after a dissociation reaction. At the temperature of 5 K, the anchored rotor shows a sequential unidirectional rotational motion through six defined stations induced by tunneling electrons. A typical voltage pulse of 400 mV applied on a specific location of the molecule causes a unidirectional rotation of 60° with a probability higher than 95%. When the temperature of the substrate increases above 20 K, the anchoring is maintained and the rotation stops being unidirectional and randomly explores the same six stations. Density functional theory simulations confirm the anchoring reaction. Experimentally, the rotation shows a clear threshold at the onset of the C–H stretch manifold, showing that the molecule is first vibrationally excited and later it decays into the rotational degrees of freedom. ; This work has received funding from the European Union's Horizon 2020 research and innovation program under the project MEMO, grant agreement no. 766864. Support by the Initiative and Networking Fund of the German Helmholtz Association, Helmholtz International Research School for Nanoelectronic Networks NanoNet (VH-KO-606) is gratefully acknowledged. Computer resources were obtained at the RES computers Finisterrae II in project RES-QCM-2019-1-0024 and Cibeles in project RES-QS-2019-3-0012 and are gratefully acknowledged. F.L. thanks the Fonds der Chemischen Industrie (FCI) for a Liebig Fellowship and C.J. the WPI MANA project for financial support. ; Peer reviewed