Suchergebnisse

HeteroNanoCarb-2019 Conference, Advances and applications in carbon related nanomaterials: From pure to doped structures including heteroatom layers, 2019, December 09th -- 13th, Centro de Ciencias de Benasque Pedro Pascual, in Benasque (Aragon, Spain). ; Graphene oxide (GO) is an elusive but highly fascinating tunable nanostructure. Dispersible in aqueous solutions, it can be easily processed into macroscopic functional materials such as papers, aerogels and thin films for different kinds of applications. Equally, it can be used as versatile platform for the formation of functional hybrid optoelectronic materials. GO-ing on with GO research, we will present our latest findings on the use of GO as unique interface layer. We will demonstrate that GO can be employed in a controllable way to enable or block charge transfer in optoelectronic device structures. Emphasis is given on the unique and highly dynamic charge-transfer interface interactions established with conjugated polymers facilitating improved thin film operation of interest for optoelectronic device structures. ; Funding by EU (Project H2020-ITN 2014 642742), Spanish MINEICO (Project ENE2016-79282-C5-1-R, AEI/FEDER) and Government of Aragon (DGA-T03-17R, FEDER, UE), is gratefully acknowledged.

Reduced graphene oxide (rGO) has been used as a support for piperazine to provide heterogeneous bifunctional organocatalyst (rGO-NH) that is able to efficiently promotvintage organic transformations such as Knoevenagel, Michael and aldol reactions. The obtained results suggest a significant role of the support in the course of these reactions ; We thank the Spanish Government (CTQ-2012-35957) and CAM (AVANCAT CS2009/PPQ-1634) for financial support. E.R. thanks the Spanish Ministry for a predoctoral fellowship (FPU/AP-2010-0807). R.S. thanks the Spanish Ministry of Science for a postdoctoral contract (PTQ-11-04601)

4 figures.-- Supplementary information available. ; Graphene oxide (GO) is widely used as a component in thin film optoelectronic device structures for practical reasons because its electronic and optical properties can be controlled. Progress critically depends on elucidating the nanoscale electronic structure of GO. However, direct experimental access is challenging because of its disordered and nonconductive character. Here, we quantitatively mapped the nanoscopic charge distribution and charge dynamics of an individual GO sheet by using Kelvin probe force microscopy (KPFM). Charge domains are identified, presenting important charge interactions below distances of 20 nm. Charge dynamics with very long relaxation times of at least several hours and a logarithmic decay of the time correlation function are in excellent agreement with Monte Carlo simulations, revealing an universal hopping transport mechanism best described by Efros–Shklovskii's law. ; This research was financed by the Ministerio de Ciencia e Innovación and the Agencia Estatal de Investigación (MICINN/AEI, Spain) and associated Funds of the European Union through the projects "Nano and Meso Scales: Modelling, Structure and Characterization" (PID2019-104272RB-C52/AEI/10.13039/501100011033 and "Photoelectrochemical hydrogen production by optimized graphene-based interfaces" (PID2019-104272RB-C51/AEI/10.13039/501100011033) and the Fundación Séneca through the projects 19907/GERM/15 and 20860/PI/18, as well as the Gobierno de Aragón (Grupo Reconocido DGA-T03_20R). ; E.C. acknowledges funding of his predoctoral contract by Spanish MINEICO and associated European Social Funds (BES2017-080020). ; Peer reviewed

Work presented at the CMAN - 2020 Online Summit on Carbon Materials and Nanotechnology, 29/09/2020, organised by STEMIO (Science Technology Engineering Mathematics International Organization). ; [Background/ Objectives and Goals] Amino-terminated oligoglycines non-covalently self-assemble, through cooperative hydrogen bonding formation, into biocompatible rigid 2D nanostructures called tectomers, either in solution or in surface-promoted processes [1,2]. We here explore the ability of tectomers to form hybrids with graphene oxide (GO), so the interaction at the interface of these 2D nanomaterials is maximized, providing new functionalities to GO. [Methods] GO/tectomer hybrids were prepared by mixing oligoglycine peptide solutions with aqueous GO solutions. The resulting composites were characterized by electron- and atomic force microscopies techniques, by UV-vis and X-ray photoelectron (XPS) spectroscopies, and contact angle measurements. [Expected Results/ Conclusion/ Contribution] Tectomers strongly interact with GO leading to GO instant flocculation and to the formation of novel multilayered hybrid assemblies. Hydrogen bonding formation accounts for the strong interfacial interaction of tectomers with GO [2]. Because of this high affinity of tectomers to GO, tectomers efficiently coat wet-spun GO fibers. We also show that, due to their versatile surface chemistry, tectomers act as supramolecular peptidic adhesives for the immobilization of a variety of carbon nanomaterials, nanoparticles, molecules and drugs on the GO fiber surface therefore allowing GO fiber functionalization. This tectomer-based functionalization strategy can be extended to other fibers, fabrics and substrates, making it very attractive for technological and smart textile applications [3]. ; This work was partially funded by the Aragón regional government (Spain, project E25_20R).

1 figure.-- Work presented at the 9th Nanodays Workshop on Advanced Materials, Munich (Germany), Sept. 13-15, 2017 ; Intrinsically conducting polymers form the base for the development of plastic electronic devices and hold great promise in optoelectronic applications such as thin film organic field-effect transitors, OLEDS and solar cells. Control of morphology and aggregation states by nanostructuring is essential for improving the device performance. In the last decade, research has focused on liquid phase assembly processes. These afford conjugated polymers in the form of nanoparticles or nanowires, which are dispersible in aqueous dispersions and allow for the fabrication of thin films with well-defined characteristics from environmentally-friendly solutions. Moreover, the liquid phase self-assembly processes provide unique opportunities for the development of novel composite materials with graphene based materials [1, 2]. Here we present our results of our recent work on the development of novel composite materials based of graphene oxide and poly (3-hexylthiophene) (P3HT) [3]. We show that liquid phase assembly processes in the presence of water-soluble graphene oxide sheets lead to the formation P3HT nanoparticles (P3HTNPs) in intimate contact with surrounding sheets of graphene oxide. During the synthesis, graphene oxide acts as a >good> solvent and induces important changes on the internal aggregation structure and the related interchain coupling. At the same time, the charge-transfer properties as a function of GO concentration are modified. Both effects are intimately coupled and lead to the stabilization of of P3HTNPs-GO donor-acceptor nanostructures offering improved charge transport and charge separation characteristics in thin films. ; Funding by EU (Project H2020-ITN 2014 642742), Spanish MINECO (ENE2013-48816-C5-5-R) and Government of Aragon (DGA-ESF-T66), is gratefully acknowledged.

The study is devoted to the possibility of surface modifying of graphene oxide with organic functional groups and/or metal nanoparticles. The presence of many oxygen-containing groups makes it possible to conduct surface methylation as well as allows them to be the centers of crystallization for metal clusters and nanoparticles. The obtained substances are characterized by different physicochemical analysis methods such as elemental analysis, x-ray diffractive analysis, IR spectroscopy and electron microscopy.

The game-changing role of graphene oxide (GO) in tuning the excitonic behavior of conjugated polymer nanoparticles is described for the first time. This is demonstrated by using poly(3-hexylthiophene) (P3HT) as a benchmark conjugated polymer and employing an in-situ re-precipitation approach resulting in P3HT nanoparticles (P3HTNPs) with sizes of 50 - 100 nm in intimate contact with GO. During the self-assembly process, GO changes the crystalline packing of P3HT chains in the forming P3HTNPs from H to H/J aggregates exhibiting exciton coupling constants as low as 2 meV, indicating favorable charge separation along the P3HT chains. Concomitantly, π-π interface interactions between the P3HTNPs and GO sheets are established resulting in the creation of P3HTNPs-GO charge-transfer complexes whose energy bandgaps are lowered by up to 0.5 eV. Moreover, their optoelectronic properties, pre-established in the liquid phase, are retained when processed into thin films from the stable aqueous dispersions, thus eliminating the critical dependency on external processing parameters. These results can be transferred to other types of conjugated polymers. Combined with the possibility of employing water based "green" processing technologies, charge-transfer complexes of conjugated polymer nanoparticles and GO open new pathways for the fabrication of improved optoelectronic thin film devices. ; This work has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 642742. AMB, and WKM acknowledge Spanish MINEICO (project ENE2016-79282-C5-1-R) and the Gobierno de Aragón (Grupo Reconocido DGA T03_17R), and associated EU Regional Development Funds). ; Peer reviewed

Semiconductor-based heterogeneous photocatalysis has been one of the most promising processes for the treatment of contaminated water. Among the available catalysts, titanium dioxide (TiO2) presents the best photocatalytic properties, being chemically and biologically inert, stable, non-toxic, cheap and easy to produce. However, its energy bang gap lies in the ultraviolet (UV) range, which is responsible for a reduced spectral activation, since UV radiation corresponds to only 5% of the solar spectrum [1]. For this reason, one of the main purposes of the scientific community has been to improve the photocatalytic performance of TiO2, namely through an adequate doping of this material, or through the creation of nanocomposites, to enable photocatalysis occurrence by the incidence of visible light. One alternative concerns the application of nanocomposites of TiO2 with graphene and graphene oxide to photocatalytic processes [2]. In this work, nanocomposites of TiO2 with different weight concentrations of graphene and graphene oxide (namely 0.5%, 1%, 1.5% and 3%) were synthetized by a one-step hydrothermal method and characterized in terms of morphology, crystalline structure, vibrational modes and optical band gap. The photocatalytic activity of these nanocomposites was then evaluated through the degradation of methylene blue and ciprofloxacin solutions under UV and visible radiation. The results indicated that the studied nanocomposites presented higher degradation rates of the methylene blue than the pure TiO2, which increased with the content of graphene/graphene oxide. However, these composites proved to be less suitable to degrade the ciprofloxacin solution than the pure TiO2 nanoparticles. ; Portuguese Foundation for Science and Technology (FCT) - UID/FIS/04650/2013, PTDC/CTM-ENE/5387/2014 and SFRH/BD/98616/2013; Basque Government Industry Department under the ELKARTEK Program. ...

A green and low-cost method was used to prepare graphene oxide (GO) and reduced graphene oxide (rGO) by chemical exfoliation of graphite powder by modified Hummers method, followed by reduction using ascorbic acid. X-ray diffractometry (XRD) and field emission scanning electron microscopy (FE-SEM) were used to analyze the structure and morphology of the synthesized materials. Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy were used to identify the formation of the GO and rGO

In this study, graphene oxide (GO) and reduced graphene oxide were synthesized by pulsed Nd:YAG laser with a fundamental wavelength (1064 nm) focused on the pure graphite target which was immersed in distilled water. Different pulse energies were applied in two cases; with and without magnetic field. The synthesized GO and rGO nanoparticles were characterized by UV-visible spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM) with and without magnetic field. The data show the presence of a magnetic field which illustrated increasing oxygen functional groups of GO. This caused a change in the morphology of the surface of GO, increasing crystallite size from 12.19 nm to 71.2 nm. The interlayer distance (d-space) was reduced from 0.4 nm to 0.25 nm and the absorption peaks that appeared in the spectrum were reduced and shifted toward smallest wavelengths, while the stretching vibration of the O-H group peak was shifted toward largest wavelengths.

Abstract
Graphene oxide nanomaterials have been developed for wide-ranging applications, but has potential safety concerns for human health. Controlled inhalation exposures in human volunteers have been a vital means to determine the effects and mechanisms of ultrafine particles in air pollution, however, few studies have used this approach to explore the effects of nanomaterials. We conducted a double-blind randomised controlled study to determine whether inhalation of graphene oxide affects pulmonary or cardiovascular function. A high purity graphene oxide was synthesised with a thickness of 1-2 layers in two sizes: 'small' (lateral dimensions: 100-1700 nm) and 'ultrasmall' (30-500 nm). Graphene oxide particles at 200 µg/m3, or filtered air, were inhaled for 2 hours by 14 young healthy volunteers on repeated visits, with measurement of cardiorespiratory parameters before and across 4 hours after exposure. Graphene oxide exposure was well-tolerated with no adverse effects. Heart rate, blood pressure, lung function and inflammatory markers were unaffected by graphene oxide irrespective of particle size. GO did not change blood biomarkers of coagulation, however, there was a mild increase in thrombus formation in an ex vivo model of arterial injury. Proteomics revealed very few differential plasma proteins. Overall, acute inhalation of graphene oxide was not associated with overt detrimental effects in healthy humans. These findings demonstrate the feasibility of carefully controlled human exposures for risk assessment of graphene nanomaterials.