Fullerol ionic fluids

http://pubs.rsc.org/en/Content/ArticlePDF/2010/NR/C0NR00307G/2010-06-08?page=SearchWe report for the first time an ionic fluid based on hydroxylated fullerenes (fullerols). The ionic fluid was synthesized by neutralizing the fully protonated fullerol with an amine terminated polyethylene/polypropylene oxide oligomer (Jeffamine(R)). The ionic fluid was compared to a control synthesized by mixing the parially protonated from (sodium form) of hte fullerols with the same oligomeric amine in the same ratio as in the ionic fluids (20 wt% fullerol). In the fullerol fluid the ionic bonding significantly perturbs the thermal transitions and melting/crystallization behavior of the amine. In contrast, both the normalized heat of fusion and crystallization of the amine in the control are similar to those of the neat amine consistent with a physical mixture of the fullerols/amine with minimal interactions. In addition to differences in thermal behavior, the fullerol ionic fluid exhibits a complex viscoelastic behavior intermediate between the neat Jeffamine (R) (liquid-like) and the control (solid-like).This publication is based on work supported in part by Award No. KUS-C1-018-02 made by King Abdullah University of Science and Technology (KAUST)

Anisotropy and magnetization reversal with chains of submicron-sized Co hollow spheres

Magnetic properties with chains of hcp Co hollow spheres have been studied. The diameter of the spheres ranges from 500 to 800 nm, with a typical shell thickness of about 60 nm. The shell is polycrystalline with an average crystallite size of 20 to 35 nm. The blocking temperature determined by the zero-field-cooling MZFC(T) measurement at H = 90 Oe is about 325 K. The corresponding effective anisotropy is determined as, Keff = 4.6*10^4 J/m^3. In addition, the blocking temperature and the effective anisotropy determined by the analysis on HC(T) are 395 K and 5.7*10^4 J/m^3, respectively. The experimentally determined anisotropy is smaller by one order of magnitude than the magnetocrystalline anisotropy of the bulk hcp Co, which is about 3 to 5*10^5 J/m^3. A further analysis on HC(T) shows that the magnetization reversal follows a nucleation rotational mode with an effective switching volume, V* = 2.3*10^3 nm^3. The corresponding effective diameter is calculated as 16.4 nm. It is slightly larger than the coherence length of Co, about 15 nm. The possible reason for the much reduced magnetic anisotropy is discussed briefly.Comment: 10 pages, 5 figures, submitted to PR

Graphene Fluoride: A Stable Stoichiometric Graphene Derivative and its Chemical Conversion to Graphene

Stoichoimetric graphene fluoride monolayers are obtained in a single step by the liquid-phase exfoliation of graphite fluoride with sulfolane. Comparative quantum-mechanical calculations reveal that graphene fluoride is the most thermodynamically stable of five studied hypothetical graphene derivatives; graphane, graphene fluoride, bromide, chloride, and iodide. The graphene fluoride is transformed into graphene via graphene iodide, a spontaneously decomposing intermediate. The calculated bandgaps of graphene halides vary from zero for graphene bromide to 3.1 eV for graphene fluoride. It is possible to design the electronic properties of such two-dimensional crystals

Graphene/Carbon Dot Hybrid Thin Films Prepared by a Modified Langmuir-Schaefer Method

The special electronic, optical, thermal, and mechanical properties of graphene resulting from its 2D nature, as well as the ease of functionalizing it through a simple acid treatment, make graphene an ideal building block for the development of new hybrid nanostructures with well-defined dimensions and behavior. Such hybrids have great potential as active materials in applications such as gas storage, gas/liquid separation, photocatalysis, bioimaging, optoelectronics, and nanosensing. In this study, luminescent carbon dots (C-dots) were sandwiched between oxidized graphene sheets to form novel hybrid multilayer films. Our thin-film preparation approach combines self-assembly with the Langmuir-Schaefer deposition and uses graphene oxide nanosheets as template for grafting C-dots in a bidimensional array. Repeating the cycle results in a facile and low-cost layer-by-layer procedure for the formation of highly ordered hybrid multilayers, which were characterized by photoluminescence, UV-visible, X-ray photoelectron, and Raman spectroscopies, as well as X-ray diffraction and atomic force microscopy.</p

Photoluminescent Carbon Dots: A Mixture of Heterogeneous Fractions

Photoluminescent carbon dots (CDs) fractions have been isolated from a gel‐like material (GM), which was synthesized using a convenient one‐step solvothermal route. In terms of purification, size exclusion chromatography (SEC) and dialysis were compared with acetone wash, which revealed the advantage of acetone wash. The pre‐purified GM with acetone wash (A‐GM) was further isolated by the reversed‐phase preparative thin layer chromatography (TLC) with acetonitrile−water mixture (7 : 3; va/vw) as the developing solvent. As a result, there were four photoluminescent bands on the TLC plate, which indicated the presence of four photoluminescent fractions. Detailed characterization measurements such as UV/Vis absorption, fluorescence emission, attenuated total reflection Fourier‐transform infrared spectroscopy, X‐ray photoelectron spectroscopy, zeta potential, dynamic light scattering, atomic force microscopy, and TEM measurements were performed on all fractions to analyze their heterogeneous optical, structural, electrical, and morphological properties. Considering the comprehensive analysis, all isolated fractions were CDs. In addition, excitation wavelength‐independent CDs were obtained with a mean size of 2.5 nm and high quantum yield (55 %). Furthermore, the study demonstrates that the excitation wavelength‐dependent photoluminescence of GM could result from the mixture of different surface states of each CD fraction rather than multiple surface states of uniform CDs nanoparticles

On a novel nanomaterial based on graphene and POSS: GRAPOSS

A novel nanomaterial which consists of graphene sheets decorated with silsesquioxane molecoles has been developed. Indeed, aminopropyl-silsesquioxane (POSS-NH2) has been employed to functionalize graphene oxide sheets (GOs). The surface grafting of GOs with POSS-NH2 has been established by infrared spectroscopy and X-ray photoelectron spectroscopy, while the morphology has been investigated by field emission electron microscopy as well as by atomic force microscopy. The combination of the amino functionalized POSS molecules with GO sheets produces a hybrid silicon/graphite-based nanomaterial, named GRAPOSS, for which the electrical conductivity of reduced GO was restored, thus allowing promising exploitations in several fields such as polymer nanocomposites.Comment: 3 pages, 4 figure

Noncovalent Functionalization of Graphene and Graphene Oxide for Energy Materials, Biosensing, Catalytic, and Biomedical Applications

This Review focuses on noncovalent functionalization of graphene and graphene oxide with various species involving biomolecules, polymers, drugs, metals and metal oxide-based nanoparticles, quantum dots, magnetic nanostructures, other carbon allotropes (fullerenes, nanodiamonds, and carbon nanotubes), and graphene analogues (MoS2, WS2). A brief description of pi-pi interactions, van der Waals forces, ionic interactions, and hydrogen bonding allowing noncovalent modification of graphene and graphene oxide is first given. The main part of this Review is devoted, to tailored functionalization for applications in drug delivery, energy materials, solar cells, water splitting, biosensing, bioimaging, environmental, catalytic, photocatalytic, and biomedical technologies. A significant part of this Review explores the possibilities of graphene/graphene oxide-based 3D superstructures and their use in lithium-ion batteries. This Review ends with a look at challenges and future prospects of noncovalently modified graphene and graphene oxideope

Synthesis of 2D Germanane (GeH):a New, Fast, and Facile Approach

Germanane (GeH), a germanium analogue of graphane, has recently attracted considerable interest because its remarkable combination of properties makes it an extremely suitable candidate to be used as 2D material for field effect devices, photovoltaics, and photocatalysis. Up to now, the synthesis of GeH has been conducted by substituting Ca by H in a beta-CaGe2 layered Zintl phase through topochemical deintercalation in aqueous HCl. This reaction is generally slow and takes place over 6 to 14 days. The new and facile protocol presented here allows to synthesize GeH at room temperature in a significantly shorter time (a few minutes), which renders this method highly attractive for technological applications. The GeH produced with this method is highly pure and has a band gap (E-g) close to 1.4 eV, a lower value than that reported for germanane synthesized using HCl, which is promising for incorporation of GeH in solar cells

Co-precipitation synthesis of reduced graphene oxide/NiAl-layered double hydroxide hybrid and its application in flame retarding poly(methyl methacrylate)

A reduced graphene oxide/NiAl-layered double hydroxide (RGO-LDH) was synthesized through a simple co-precipitation route. NiAl-layered double hydroxide (NiAl-LDH) nanoparticles were homogeneously dispersed on the reduced graphene oxide (RGO) nanosheets, which were simultaneously reduced during the process. RGO-LDH exhibited three steps of weight loss, leaving high residue. RGO-LDH was then solution blended into poly(methyl methacrylate) (PMMA) to investigate its effect on reducing flammability of the composite. With the incorporation of RGO-LDH, the thermal stability of PMMA composite was improved. Moreover, RGO-LDH endowed PMMA with the largest reduction in the heat release rate, smoke production and CO production rate relative to RGO or NiAl-LDH alone. RGO-LDH could decrease the production of volatiles including hydrocarbons, carbonyl compounds and epoxy compounds from the PMMA composite. The improved flame retardancy was ascribed to the combined effect of the physical barrier of RGO and the catalytic carbonization of NiAl-LDH. © 2013 Elsevier Ltd. All rights reserved