Suchergebnisse

Available online March 22, 2013.- El pdf del artículo es la versión post-print.-Supplementary data associated with this article can be found on pages 21-23. ; We here present an effective strategy to prepare enhanced composites using poly(vinyl alcohol) (PVA) and multiwalled carbon nanotubes (MWCNT). It contains two essential steps. First, the elaboration of homogeneous aqueous MWCNT dispersions and the selection of the most effective dispersing agent. In a sequential dispersion protocol for seven common dispersants, including surfactants and polymers, the dispersion quality and dispersion ability, independent of the intrinsic nature of the dispersing agent were established using zeta-potential and UV-Vis-spectroscopy. Second, the combination of the most effective dispersing agent, namely dodecylbenzenesulfonate (SDBS) with a polymer dispersant of high affinity towards the PVA matrix, namely polyvinylpyrrolidone (PVP). This resulted in homogeneous PVA-MWCNT composites with significantly improved glass transition temperature by up to 12 ºC as a function of the sequential order of dispersant addition. The presented dispersion strategy is straightforward and thus may provide a fast, reliable and general guide for fabricating nanotube composites with improved performance. ; This research was supported by Spanish Ministry of Science and Innovation (MICINN) under project MAT2010-15026, CSIC under project 201080E124, and the Government of Aragon (DGA) under project DGA-T66 CNN. The authors thank Nanocyl S.A. (Sambreville, Belgium) for providing nanotube samples. ; Peer reviewed

6 pages, 2 figures, 2 tables.- First published online 26 April, 2013 ; The synthesis of Pd nanoparticles (Pd-NPs) supported on multiwalled carbon nanotubes (MWCNTs) and the catalytic performance of the resulting material (Pd-NPs/MWCNTs) on hydrogenation reactions are presented. Facile preparation approaches based on the decomposition of Pd precursors in the presence of MWCNTs lead to homogeneous dispersions of supported Pd-NPs with average size of 4 nm and Pd loads about 12%. The catalytic performance of this material was evaluated in hydrogenation reactions of α,β-unsaturated ketones, alkenes, cyclic di-, tri-and tetraenes, aromatic compounds, terpenes and terpenoids, resulting in very high activity offering short reaction times, high conversion rates, notable selectivity, and acceptable recyclabitiliy under mild conditions. ; Financial support from the Spanish Ministerio de Economía y Competitividad (MINECO) and the European Regional Development Fund (ERDF) under projects CTQ2011-22589 and MAT2010-15026, CSIC under project 201080E124, and the Regional Government of Aragon and the European Social Fund (ESF) under projects (DGA-PI086-08 and E-97, and DGA-ESF T66 CNN) is gratefully acknowledged. M. C. thanks MICINN and ESF for her Grant Nº BES- 2008-003503. ; Peer reviewed

The type and distribution of oxygen functional groups in graphene oxide and reduced graphene oxide remain still a subject of great debate. Local analytic techniques are required to access the chemistry of these materials at a nanometric scale. Electron energy loss spectroscopy in a scanning transmission electron microscope can provide the suitable resolution, but GO and RGO are extremely sensitive to electron irradiation. In this work we employ a dedicated experimental set-up to reduce electron illumina- tion below damage limit. GO oxygen maps obtained at a few nanometres scale show separated domains with diferent oxidation levels. The C/O ratio varies from about 4:1 to 1:1, the latter corresponding to a complete functionalization of the graphene flakes. In RGO the residual oxygen concentrates mostly in regions few tens nanometres wide. Specific energy-loss near-edge structures are observed for diferent oxidation levels. By combining these findings with first principles simulations we propose a model for the highly oxidized domains where graphene is fully functionalized by hydroxyl groups forming a 2D-sp3 carbon network analogous to that of graphane. ; AT, AZ and OS acknowledge support from the Agence Nationale de la Recherche (ANR), program of future investment TEMPOS-CHROMATEM (No. ANR-10-EQPX-50). The work has also received funding from the European Union in Seventh Framework Programme (No. FP7/2007 -2013) under Grant Agreement No. n312483 (ESTEEM2). AMB and WKM are grateful for Financial support from the Spanish Ministry MINECO and the European Regional development Fund (project ENE2013-48816-C5-5-R) and from the Regional Government of Aragon and the European Social Fund (DGA-ESF-T66 Grupo Consolidado). The authors are grateful to P. Launois, S. Rouziere and C.P. Ewels for useful discussion. ; Peer reviewed

Gold nanoparticles (AuNPs) with sizes between 3 and 10 nm were firmly supported on pristine multi-walled carbon nanotubes (MWCNT) in high yields by a facile linker-free deposition route using aqueous suspensions of pre-reduced gold precursors. For the first time, the resulting AuNP-MWCNT hybrid material was employed as catalyst for the hydrogenation of a series of substituted nitroarenes under mild reaction conditions. High catalytic activity with turnover frequencies (TOF) values up to 1200 h-1 were achieved accompanied by a remarkable chemoselectivity. Recyclability tests did neither reveal leaching nor changes in size or oxidation states of the AuNPs. The concomitant presence of Au0 and AuI accounts for both the superior catalytic performance and the high stability of the hybrid material. Preferential orientation of nitroarenes on the MWCNT surface due to π-π interactions coupled with coulombic contact of the nitro group to the AuNPs most likely explains the high chemoselectivity of the hybrid material, and further underlines the valuable role of MWCNTs for catalytic reactions. ; Financial support from Spanish MINECO and the European Regional Development Fund (projects MAT2010-15026, ENE2013-48816-C5-5-R and CTQ2011-22589), Spanish National Research Council CSIC (project 201080E124), and Regional Government of Aragon and the European Social Fund DGA-ESF (T66 Grupo Consolidado, E-97, and E-26) is gratefully acknowledged. ; Peer reviewed

In this work, a novel amperometric biosensor based on gold nanoparticles anchored on reduced graphene oxide (RGO-AuNPs) and L-lactate dehydrogenase (LDH) was developed for the sensing of Llactate. Firstly, the RGO-AuNPs modified screen printed electrodes were tested for NADH detection showing a wide dynamic range and a low detection limit. Next, the biosensor was constructed by incorporating both enzyme and RGO-AuNPs in a sol gel matrix derived from tetrametoxysilane and methyltrimetoxysilane. The enzyme loading, working pH, and coenzyme concentration were optimized. The biosensor linearly responded to L-lactate in the range of 10 μM - 5 mM and showed a good specific sensitivity of 154 μA/mM·cm2 with a detection limit of 0.13 μM. This was accompanied by good reproducibility and operational stability. Tests on artificial serum proved that L-lactate can be determined practically without interferences from commonly interfering compounds such as urate, paracetamol and L-ascorbate. Our LDH/RGO-AuNPs/SPCE based biosensor thus performs as electrochemical device for the detection of L-lactate as a viable early cancer bio-marker. ; This work was supported by Romanian National Authority for Scientific Research, grant PN-IIID- PCE-2011-3-0286 and FP7 Marie Curie PIRSES_GA_2012-318053: SMARTCANCERSENS. Ana M. Benito and Wolfgang K. Maser would like to thank the Spanish Ministry MINECO (Projects MAT2010-15026 and ENE2013-48816-C5-5-R), the Spanish National Research Council CSIC (Project 201080E124), and the regional Government of Aragon and the European Social Fund (Project DGA-ESF T66) for financial support. ; Peer reviewed

5 pages, 3 Figures, Supplementary Data ; In this communication we present a potentiometric aptasensor based on chemically modified graphene (transducer layer of the aptasensor) and aptamers (sensing layer). Graphene oxide (GO) and reduced graphene oxide (RGO) are the basis for the construction of two versions of the aptasensor for the detection of a challenging living organism such as Staphylococcus aureus. In these two versions, DNA aptamers are either covalently (in the GO case) or non-covalently (in the RGO case) attached to the transducer layer. In both cases we are able to selectively detect a single CFU/mL of S. aureus in an assay close to real time, although the noise level associated to the aptasensors made with RGO is lower than the ones made with GO. These new aptasensors, that show a high selectivity, are characterized by the simplicity of the technique and the materials used for their construction while offering ultra-low detection limits in very short time responses in the detection of microorganisms. ; Spanish Ministry of Science and Innovation (MICINN) through project grants CTQ2010-18717, MAT2010-15026 ; Spanish Higher Research Council CSIC under project 201080E124 ; Regional Government of Aragon and the European Social Fund under project DGA-FSE-T66 CNN ; Peer reviewed

We report on the growth of non-stoichiometric nanocrystalline hydroxyapatite (nHAp) with a composition similar to natural bone by a wet-chemical in-situ precipitation route on carbon nanotubes (CNTs) with different degrees of oxygen functionalities and on graphene oxide (GO). Both, functionalization degree and morphology of CNTs and GO appear as critical parameters controlling the shape and crystallinity of the self-assembled nHAp nanoparticles in the corresponding composite materials. Crystalline nHAp nanoparticles with rod-like morphology were achieved for moderately oxidized CNTs and for GO. On CNTs these grow along the CNT's axis while on GO they form a compact layer. In both cases enhanced nHAp integration onto the respective carbon support is obtained. In vitro bioactivity of the prepared composites exhibits a fast apatite biomineralization process, induced by the presence of nHAp. Depending on its crystalline size and dispersion degree remineralization of the apatite nanoparticles takes place through the inclusion of PO4 3 and CO32 by ion exchange. Importantly, during the stage of bioactivity the integration degree of nHAp nanoparticles on the carbon nanostructures alters with time, evidencing the potential of GO as valuable bioceramic support material. ; Spanish Ministry MINECO (project MAT201015026 ; Spanish National Research Council CSIC (project 201080E124, and PhD grant JAEPre09-01155) ; Regional Government of Aragon and the European Social Fund (DGA-ESF-T66 Grupo Consolidado) ; EU COST network MP0901 NanoTP ; EU 7th Framework Program (Grant Agreement 312483-ESTEEM2) ; Peer reviewed

Resumen del trabajo presentado al ChemOnTubes, celebrado en Bruselas (Bélgica) del 3 al 7 de abril de 2016. ; This work has been funded by MINECO and European Regional Development Fund (ENE2013-48816-C5-5-R NANOSOL-MAT), CSIC (project 2015801011 Intramural), Government of Aragón and European Social Fund (DGA-ESF-T66 Grupo Consolidado) and European Commission (H2020-MSCA-ITN-2014-ETN 642742 Enabling Excellence). ; Peer reviewed

Resumen del trabajo presentado al HeteroNanoCarb: "Advances and Applications in Carbon Related Nanomaterials: From pure to doped structures including heteroatom layers", celebrado en Benasque (España) del 7 al 11 de diciembre de 2015. ; This work has been funded by the Spanish Ministry MINECO and the European Regional Development Fund under the project ENE2013-48816-C5-5-R, and the Government of Aragon and the European Social Fund (DGA-ESF-T66 Grupo Consolidado). ; Peer reviewed

Resumen del trabajo presentado al Nanomath, celebrado en Toulouse (Francia) del 27 al 30 de junio de 2016. ; This work has been funcled by MINECO ancl Europea.n Regional Development Funcl (ENE2013-48816-C5-5-R "NANOSOL-MAT"), CSIC (project 2015801011 "Int.ramural"), Government of Aragón and European Social Fund (DGA-ESF-T66 "Grupo Consolidado") ancl European Commission (H2020-MSCA-ITN-2014-ETN 642742 "Enabling Excellcnce"). ; Peer reviewed

9 pages, 9 figures.-- Available online 21 February 2014 ; The effect of -irradiation on the structure and composition of chemically synthesized few-layered graphene materials was studied. Fully oxidized graphene oxide and graphene nanoribbons, as well as their respective chemically post-reduced forms, were treated under -irradiation in an air-sealed environment. Three different irradiation doses of 60, 90 and 150 kGy were applied. Structure and composition of the irradiated materials were analyzed by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Raman spectroscopy and Xray photoelectron spectroscopy (XPS). The XRD patterns were not affected by - irradiation, and small changes were observed in the FTIR and TGA results. However, significant modifications were detected by Raman spectroscopy and XPS, particularly in the Raman G/D band intensity ratios and in the C 1s XPS profiles. Comparatively, the changes in Raman and XPS spectra after -irradiation were even greater than those occurring during the chemical reduction of graphene oxides. Our results indicate that the graphene carbon lattice was strongly affected by -irradiation, but the materials experienced small variations in their oxygen content. ; This work was funded by the Spanish MINECO under the projects TEC2010-15736, MAT2010-15026, MAT2010-16175 (CICYT) and PRI-PIBAR-2011-1, CSIC under Project 201080E124 and the Government of Aragon (DGA) and the European Social Fund (ESF) under Project DGA-ESF-T66 CNN. ; Peer reviewed