Suchergebnisse

We report on the stepwise formation of N-doped nanohelicenes, nanographenes, nanodomes and graphenes from the same heteroaromatic precursor through subsequent dehydrogenations on Pt(111) upon thermal annealing. The combined experimental (UHV-STM) and computational (DFT) studies provide a full atomistic description of the intermediate reaction stages. This journal is © The Royal Society of Chemistry. ; This work is supported by Spanish research projects MAT 2011-26534 and CSD2007-41, European Union Seventh Framework Programme under the grant agreement no 604391 Graphene Flagship, the Czech Science Foundation (P207/10/2207) and the Institute of Organic Chemistry and Biochemistry AS CR (RVO: 61388963). JIM acknowledges the CSIC-JAEDOC Fellowship Program. ; Peer Reviewed

Understanding the connection of graphene with metal surfaces is a necessary step for developing atomically precise graphene-based technology. Combining high-resolution STM experiments and DFT calculations, we have unambiguously unveiled the atomic structure of the boundary between a graphene zigzag edge and a Pt(111) step. The graphene edges minimize their strain by inducing a 3-fold edge-reconstruction on the metal side. We show the existence of an unoccupied electronic state that is mostly localized on the C-edge atoms of one particular graphene sublattice, which could have implications in the design of graphene based devices. © 2014 American Chemical Society. ; We acknowledge financial support from Spanish Grants MAT2010-17720, MAT2011-23627, MAT2011-26534, CSD2008-00041, CSD2010-00024, PLE2009-0061 (MINECO, Spain) and S2009/MAT-1467 (CAM, Spain). The research leading to these results has received funding from the European Union Seventh Framework Programme under Grant agreement No. 604391 Graphene Flagship. P.P. and P.M. were supported by the Ramón y Cajal and "Rafael Calvo Rodés" programs, respectively. ; Peer Reviewed

The intrinsic atomic mechanisms responsible for electronic doping of epitaxial graphene Moirés on transition metal surfaces is still an open issue. To better understand this process we have carried out a first-principles full characterization of the most representative Moiré superstructures observed on the Gr/Pt(111) system and confronted the results with atomically resolved scanning tunneling microscopy experiments. We find that for all reported Moirés the system relaxes inducing a non-negligible atomic corrugation both, at the graphene and at the outermost platinum layer. Interestingly, a mirror "anti-Moiré" reconstruction appears at the substrate, giving rise to the appearance of pinning-points. We show that these points are responsible for the development of the superstructure, while charge from the Pt substrate is injected into the graphene, inducing a local n-doping, mostly localized at these specific pinning-point positions. ; We acknowledge funding from the Spanish MINECO (Grant MAT2014-54231-C4-1-P), the EU via the ERC-Synergy Program (Grant ERC-2013-SYG-610256 Nanocosmos), and computing resources from CTI-CSIC. The research leading to these results has received funding from the European Union Seventh Framework Programme under Grant agreement No. 604391 Graphene Flagship. J.I.M. acknowledges funding from both the CSIC-JaeDoc Fellowship Program (co-funded by the European Social Fund) and Nanocosmos. P.M. was supported by the "Rafael Calvo Rodés" Program. ; Peer reviewed

The properties of water at the nanoscale are crucial in many areas of biology, but the confinement of water molecules in sub-nanometre channels in biological systems has received relatively little attention. Advances in nanotechnology make it possible to explore the role played by water molecules in living systems, potentially leading to the development of ultrasensitive biosensors. Here we show that the adsorption of water by a self-assembled monolayer of single-stranded DNA on a silicon microcantilever can be detected by measuring how the tension in the monolayer changes as a result of hydration. Our approach relies on the microcantilever bending by an amount that depends on the tension in the monolayer. In particular, we find that the tension changes dramatically when the monolayer interacts with either complementary or single mismatched single-stranded DNA targets. Our results suggest that the tension is mainly governed by hydration forces in the channels between the DNA molecules and could lead to the development of a label-free DNA biosensor that can detect single mutations. The technique provides sensitivity in the femtomolar range that is at least two orders of magnitude better than that obtained previously with label-free nanomechanical biosensors and with label-dependent microarrays. ; D.R. acknowledges the fellowship funded by the Autonomic Community of Madrid (CAM). J.T, M.C, J.M and D.R acknowledge financial support by Spanish Ministry of Science (MEC) under grant No. TEC2006-10316 and CAM under grant No. 200550M056. C.B. acknowledges funding provided by MEC under grant No. BIO2007-67523. Work at Centro de Astrobiología was supported by European Union (EU), Instituto Nacional de Técnica Aeroespacial (INTA), MEC and CAM. All the authors acknowledge A. Cebollada, J.M. García-Martín, J. García, J.L. Costa-Kramer, M. Arroyo-Hernández and J.V. Anguita for their assistance in the gold deposition on the cantilevers. ; Peer reviewed

The hydrogen (H) dimer structures formed upon room-temperature H adsorption on single layer graphene (SLG) grown on SiC(0001) are addressed using a combined theoretical–experimental approach. Our study includes density functional theory (DFT) calculations for the full (6√3 × 6√3)R30° unit cell of the SLG/SiC(0001) substrate and atomically resolved scanning tunneling microscopy images determining simultaneously the graphene lattice and the internal structure of the H adsorbates. We show that H atoms normally group in chemisorbed coupled structures of different sizes and orientations. We make an atomic scale determination of the most stable experimental geometries, the small dimers and ellipsoid-shaped features, and we assign them to hydrogen adsorbed in para dimers and ortho dimers configuration, respectively, through comparison with the theory. ; P.M acknowledges financial support from a R. C. Rodes grant. The research leading to these results has received funding from the European Union Seventh Framework Program under grant agreement no. 604391 Graphene Flagship. We acknowledge financial support by the Spanish project MAT2011-26534. M.S., P.M., and P.J acknowledge the financial support of GACR project no. 14-02079S. ; Peer reviewed

The electronic structure of the TiO2 (110)-(1 × 2) surface has been studied by means of angular resolved ultraviolet photoemission spectroscopy (ARUPS). The valence band dispersion along the high symmetry surface directions, [001] and [1–10], has been recorded. The experimental data show no dispersion of the band-gap Ti 3d states. However, the existence of dispersive bands along the [001] direction located at about 7 eV below the Fermi level is reported. The existence of two different contributions in the emission from the defects-related state located in the gap of the surface is univocally shown for the first time. ; This work has been supported by the Spanish CYCIT (MAT2011-26534) and the Ministry of Science and Innovation (CSD2007-41 NANOSELECT). C.S.S. gratefully acknowledges Ministerio de Educación for the financial support inside the "FPU programme" under the AP2005-0433 grant. M.G. G. and P.A. are grateful for the support by the Fonds National Suisse pour la Recherche Scientifique through Div. II and the Swiss National Center of Competence in Research MaNEP. M.B.-R. acknowledges financial support from the Gipuzkoako Foru Aldundia and the European Union 7th Framework Programme (FP7/2007–2013) under grant agreement no. FP7-PEOPLE-2010-RG276921. ; Peer reviewed

We investigated the adsorption of pentacene on the (111) surface of platinum, which is an archetypal system for a junction with a low charge-injection barrier. We probed the structural and electronic configurations of pentacene by scanning tunnelling microscopy (STM), X-ray photoemission spectroscopy (XPS), and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy measurements. We simulated the interface by means of ab initio methods based on the density functional theory (DFT) framework, while including the dispersion forces. We found that the molecules adsorb at the bridge site of the close-compact atom rows with the long axis parallel to the substrate's directions, in a slightly distorted geometry, driven by the good match between the position of the carbon atoms of the molecule and the underlying lattice of the surface. Most importantly, a chemical bond is formed at the interface, which we attribute to the high chemical reactivity of the Pt substrate. ; This work was performed in the PCAM network of European doctorate. S.S.H. acknowledges support from the European Union Seventh Framework Programme under grant agreement no. 607232 (THINFACE) and the computing infrastructure at the Vienna Scientific Cluster. L.F. acknowledges financial support from CNR-INFN national project (PREMIALE 2012) EOS 'Organic Electronics for Innovative research instrumentation'. ESISNA group acknowledge funding from MAT2014-54231-C4-1-P. ; Peer reviewed

We have deposited 4-aminophenol on Pt(111) surfaces in ultra-high vacuum and studied the strength of its adsorption through a combination of STM, LEED, XPS and ab initio calculations. Although an ordered (2√3 × 2√3)R30° phase appears, we have observed that molecule–substrate interaction dominates the adsorption geometry and properties of the system. At RT the high catalytic activity of Pt induces aminophenol to lose the H atom from the hydroxyl group, and a proportion of the molecules lose the complete hydroxyl group. After annealing above 420 K, all deposited aminophenol molecules have lost the OH moiety and some hydrogen atoms from the amino groups. At this temperature, short single-molecule oligomer chains can be observed. These chains are the product of a new reaction that proceeds via the coupling of radical species that is favored by surface diffusion. ; We acknowledge funding from the Spanish MINECO (Grants MAT2014-54231-C4-1-P, MAT2014-54231-C4-4-P and MAT2013-47898-C2-2-R), the EU via the ERC-Synergy Program (Grant ERC-2013-SYG-610256 NANOCOSMOS), and computing resources from CTI-CSIC. MKS and GOI acknowledge financial support from FCT (Grant No. PTDC/CTM-NAN/121108/2010 and SFRH/BPD/90562/2012), Ministry of Science and Technology, Portugal. HJS would like to acknowledge the MICINN for a "Ramón y Cajal" Senior Research Fellowship, Spain. JIM acknowledges funding from both the CSIC-JAE-Doc Fellowship Program (co-funded by the European Social Fund). The research leading to these results has received funding from the European Union Seventh Framework Programme under Grant agreement No. 604391 Graphene Flagship. ; Peer reviewed

[EN] On-surface synthesis, complementary to wet chemistry, has been demonstrated to be a valid approach for the synthesis of tailored graphenic nanostructures with atomic precision. Among the different existing strategies used to tune the optoelectronic and magnetic properties of these nanostructures, the introduction of non-hexagonal rings inducing out-of-plane distortions is a promising pathway that has been scarcely explored on surfaces. Here, we demonstrate that non-hexagonal rings, in the form of tropone (cycloheptatrienone) moieties, are thermally transformed into phenyl or cyclopentadienone moieties upon an unprecedented surface-mediated retro–Buchner-type reaction involving a decarbonylation or an intramolecular rearrangement of the CO unit, respectively. ; We acknowledge the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (ERC-2015-STG-677023 and ERC-2013-SYG-610256 NANOCOSMOS) and the innovation program under grant agreement No. 696656 (GrapheneCore1-Graphene-based disruptive technologies) and grant agreement No. 785219 (GrapheneCore2-Graphenebased disruptive technologies) for financial support. Grants PGC2018-101181-B-I00 and MAT2017- 85089-C2-1-R funded by MCIN/AEI/10.13039/501100011033 and "ERDF A way of making Europe" by the "European Union", and grant PID2020-113142RB-C21 funded by MCIN/AEI/ 10.13039/501100 011033 also provided financial support. We also acknowledge Comunidad de Madrid via Programade Investigación Tecnologías 2018 (FOTOART-CM S2018/NMT-4367), the Swiss National Science Foundation (grant number 200020-182015), the NCCR MARVEL funded by the Swiss National Science Foundation (grant number 51NF40-182892) and FEDER/Junta de Andalucía-Consejería de Economía y Conocimiento (B-FQM-428-UGR20). C. S. S. and N. R. A. acknowledge Grants RYC2018-024364-I and BES-2015-072642, respectively, funded by MCIN/AEI/ 10.13039/501100011033 and "ESF Investing in your future". I. R. M. acknowledges the University of Granada for her postdoctoral contract (Contrato Puente-Plan Propio UGR). F.V. thanks Ministerio de Universidades for the FPU grant (FPU18/05938). ; Peer reviewed

Herein we describe a distorted ribbon-shaped nanographene exhibiting unprecedented combination of optical properties in graphene-related materials, namely upconversion based on two-photon absorption (TPA-UC) together with circularly polarized luminescence (CPL). The compound is a graphene molecule of ca. 2 nm length and 1 nm width with edge defects that promote the distortion of the otherwise planar lattice. The edge defects are an aromatic saddle-shaped ketone unit and a [5]carbohelicene moiety. This system is shown to combine two-photon absorption and circularly polarized luminescence and a remarkably long emission lifetime of 21.5 ns. The [5]helicene is responsible for the chiroptical activity while the push–pull geometry and the extended network of sp2 carbons are factors favoring the nonlinear absorption. Electronic structure theoretical calculations support the interpretation of the results. ; This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (ERC-2015-STG-677023). We also thank the Ministerio de Economía y Competitividad (MINECO, Spain) (CTQ2015-70283-P, CTQ2014-53598-R, MAT2014-54231-C4-1P, FIS2016-77578-R) and the "Unidad de Excelencia Química Aplicada a Biomedicina y Medioambiente (UGR)". A. G. C., C. S. S. and C. M. C. acknowledge funding from MINECO (Spain) for RyC-2013-12943, IJCI-2014-19291 and BES-2016-076371 contracts, respectively. I. R. M. thanks UGR (Spain) for a postdoctoral scholarship. I. M. and E. M. thank the Fundação para a Ciência e a Tecnologia for financial support (IF/00759/2013 and post-doc grant SFRH/BPD/75782/2011). We thank the CSIRC-Alhambra for supercomputing facilities.

13 pags., 8 figs. -- Open Access funded by Creative Commons Atribution Licence 4.0 ; The increasing demand for nanostructured materials is mainly motivated by their key role in a wide variety of technologically relevant fields such as biomedicine, green sustainable energy or catalysis. We have succeeded to scale-up a type of gas aggregation source, called a multiple ion cluster source, for the generation of complex, ultra-pure nanoparticles made of different materials. The high production rates achieved (tens of g/day) for this kind of gas aggregation sources, and the inherent ability to control the structure of the nanoparticles in a controlled environment, make this equipment appealing for industrial purposes, a highly coveted aspect since the introduction of this type of sources. Furthermore, our innovative UHV experimental station also includes in-flight manipulation and processing capabilities by annealing, acceleration, or interaction with background gases along with in-situ characterization of the clusters and nanoparticles fabricated. As an example to demonstrate some of the capabilities of this new equipment, herein we present the fabrication of copper nanoparticles and their processing, including the controlled oxidation (from Cu to CuO through CuO, and their mixtures) at different stages in the machine. ; This work was supported by the European Union [grant number ERC-2013-SyG 610256 NANOCOSMOS]; the Spanish MINECO [grant numbers MAT2017-85089-C2-1-R, MAT2014-54231-C4-1-P, MAT2014-54231- C4-4-P, MAT2014-59772-C2-2-P, FIS2016-77578-R, FIS2013-48087-C2-1P, FIS2016-77726-C3-1P and CSIC13-4E-1775]. ; Peer Reviewed

Graphene functionalization with organics is expected to be an important step for the development of graphene-based materials with tailored electronic properties. However, its high chemical inertness makes difficult a controlled and selective covalent functionalization, and most of the works performed up to the date report electrostatic molecular adsorption or unruly functionalization. We show hereafter a mechanism for promoting highly specific covalent bonding of any amino-terminated molecule and a description of the operating processes. We show, by different experimental techniques and theoretical methods, that the excess of charge at carbon dangling-bonds formed on single-atomic vacancies at the graphene surface induces enhanced reactivity towards a selective oxidation of the amino group and subsequent integration of the nitrogen within the graphene network. Remarkably, functionalized surfaces retain the electronic properties of pristine graphene. This study opens the door for development of graphene-based interfaces, as nano-bio-hybrid composites, fabrication of dielectrics, plasmonics or spintronics. ; The research leading to these results has received funding from the Spanish MINECO (through Grants No. MAT2014-54231-C4-1-P, MAT2016-80394-R, RYC-2014-16626 and RYC-2015-17730), from the EU via the ERC-Synergy Program (Grant No. ERC-2013-SYG-610256 Nanocosmos) and the European Union Seventh Framework Program (Grant No. 604391 Graphene Flagship), and from the Comunidad Autónoma de Madrid (CAM) via the MAD2D-CM Program (Grant No. S2013/MIT-3007). We also thank the computing resources from CTI-CSIC. R.L. acknowledges financial support from Spanish MINECO under Grant agreement No. CONSOLIDER INGENIO CSD2009-00013. ; Peer reviewed

I. Tanarro et al. -- 16 pags., 18 figs., app. ; We present a proof of concept on the coupling of radio astronomical receivers and spectrometers with chemical reactors and the performances of the resulting setup for spectroscopy and chemical simulations in laboratory astrophysics. Several experiments including cold plasma generation and UV photochemistry were performed in a 40 cm long gas cell placed in the beam path of the Aries 40 m radio telescope receivers operating in the 41–49 GHz frequency range interfaced with fast Fourier transform spectrometers providing 2 GHz bandwidth and 38 kHz resolution. The impedance matching of the cell windows has been studied using di erent materials. The choice of the material and its thickness was critical to obtain a sensitivity identical to that of standard radio astronomical observations. Spectroscopic signals arising from very low partial pressures of CH3OH, CH3CH2OH, HCOOH, OCS, CS, SO2 (<103 mbar) were detected in a few seconds. Fast data acquisition was achieved allowing for kinetic measurements in fragmentation experiments using electron impact or UV irradiation. Time evolution of chemical reactions involving OCS, O2 and CS2 was also observed demonstrating that reactive species, such as CS, can be maintained with high abundance in the gas phase during these experiments ; The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC-SyG-2013 Grant Agreement No. 610256 NANOCOSMOS and from spanish MINECO CSD2009-00038 (ASTROMOL) under the Consolider-Ingenio Program. We also thank spanish MINECO for funding under grants AYA2012-32032, AYA2016-75066-C2-1-P, FIS2013-48087-C2-1-P, FIS2016-77726-C3-1-P, FIS2016-77578-R, MAT2014- 54231-C4-1-P. ; Peer reviewed

Technologically useful and robust graphene-based interfaces for devices require the introduction of highly selective, stable, and covalently bonded functionalities on the graphene surface, whilst essentially retaining the electronic properties of the pristine layer. This work demonstrates that highly controlled, ultrahigh vacuum covalent chemical functionalization of graphene sheets with a thiol-terminated molecule provides a robust and tunable platform for the development of hybrid nanostructures in different environments. We employ this facile strategy to covalently couple two representative systems of broad interest: metal nanoparticles, via S–metal bonds, and thiol-modified DNA aptamers, via disulfide bridges. Both systems, which have been characterized by a multitechnique approach, remain firmly anchored to the graphene surface even after several washing cycles. Atomic force microscopy images demonstrate that the conjugated aptamer retains the functionality required to recognize a target protein. This methodology opens a new route to the integration of high-quality graphene layers into diverse technological platforms, including plasmonics, optoelectronics, or biosensing. With respect to the latter, the viability of a thiol-functionalized chemical vapor deposition graphene-based solution-gated field-effect transistor array was assessed. ; This work was supported by the European Union's Horizon 2020 research and innovation programme under grant agreement No 696656 (Graphene Flagship-core 1) and no 785219 (Graphene Flagship −core 2); UE FP7 ideas: ERC (grant ERC-2013-SYG-610256 Nanocosmos) and Spanish MINECO grants MAT2014-54231-C4-1-P, MAT2014-54231-C4-4-P, MAT2017-85089-C2-1-R, MAT2014-59772-C2-2-P, and BIO2016-79618-R (funded by EU under the FEDER programme), as well as the Nanoavansens program from the Community of Madrid (S2013/MIT-3029). This work has made use of the Spanish ICTS Network MICRONANOFABS partially supported by MINECO and also the ICTS NANBIOSIS, more specifically the Micro-Nano Technology Unit of the CIBER in Bioengineering, Biomaterials & Nanomedicine (CIBER-BBN) at the IMB-CNM. We are grateful to Matthias Muntwiler for his assistance with experiments in the PEARL beamline in the SLS facility. Finally, we acknowledge the TEM and ICP services at the CNB and ICMM institutes, respectively. CSS acknowledges the MINECO for a Juan de la Cierva Incorporación grant (IJCI-2014-19291). M. Marciello is grateful to the Comunidad de Madrid (CM) and European Social Fund (ESF) for supporting her research work through the I+D Collaborative Programme in Biomedicine NIETO-CM (B2017-BMD3731). ; Peer reviewed

8 pags, 4 figs. -- The online version contains supplementary material available at https://doi.org/10.1038/s41467-021-26184-0 ; Development of sustainable processes for hydrocarbons synthesis is a fundamental challenge in chemistry since these are of unquestionable importance for the production of many essential synthetic chemicals, materials and carbon-based fuels. Current industrial processes rely on non-abundant metal catalysts, temperatures of hundreds of Celsius and pressures of tens of bars. We propose an alternative gas phase process under mild reaction conditions using only atomic carbon, molecular hydrogen and an inert carrier gas. We demonstrate that the presence of CH2 and H radicals leads to efficient C-C chain growth, producing micron-length fibres of unbranched alkanes with an average length distribution between C23-C33. Ab-initio calculations uncover a thermodynamically favourable methylene coupling process on the surface of carbonaceous nanoparticles, which is kinematically facilitated by a trap-and-release mechanism of the reactants and nanoparticles that is confirmed by a steady incompressible flow simulation. This work could lead to future alternative sustainable synthetic routes to critical alkane-based chemicals or fuels. ; We thank Jose Criado for the artwork schematics of the system, in figures 4 and S1; Funding: We thank the European Research Council for funding support under Synergy grant ERC-2013-SyG, G.A. 610256 (NANOCOSMOS). Also, we acknowledge partial support from the Spanish MINECO through grants PID2020-113142RB-C21, PID2019106315RB-I00, and PID2019-106315RB-I00, EU ERC CoG HyMAP 648319, and from the regional government through project S2018-NMT-4367 (FotoArt-CM). AM acknowledges to the Spanish Ministry of Science (RYC2018-024561-I), to the Regional Government of Aragon (DGA E13_20R), to the National Natural Science Foundation of China (NFSC-21850410448, NSFC-21835002), and to the The Centre for Highresolution Electron Microscopy (ChEM), supported by SPST of ShanghaiTech University under contract No. EM02161943. S.K. and G.H. acknowledge funding from the Turbulent Superstructures Program of the German National Science Foundation (DFG) ; Peer reviewed