Ultrasound exfoliation of inorganic analogues of graphene

High-intensity ultrasound exfoliation of a bulk-layered material is an attractive route for large-scale preparation of monolayers. The monolayer slices could potentially be prepared with a high yield (up to 100%) in a few minutes. Exfoliation of natural minerals (such as tungstenite and molybdenite) or bulk synthetic materials (including hexagonal boron nitride (h-BN), hexagonal boron carbon nitride (h-BCN), and graphitic carbon nitride (g-C(3)N(4))) in liquids leads to the breakdown of the 3D graphitic structure into a 2D structure; the efficiency of this process is highly dependent upon the physical effects of the ultrasound. Atomic force microscopy (AFM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) were employed to verify the quality of the exfoliation. Herein, this new method of exfoliation with ultrasound assistance for application to mono- and bilayered materials in hydrophobic and hydrophilic environments is presented

Carbon and zeolite-based composites for radionuclide and heavy metal sorption

Zeolites have been investigated as sorbents of heavy metals from water. Since graphene oxide was already reported as promising radionuclide sorbent, we developed composite materials containing both a synthetic zeolite (type A, P or Y) and graphene oxide to be multifunctional sorbents. The extension of multifunctionality of sorbents was done by presence of third component, exfoliated graphite, to have additional properties as conductivity. The changing sorption activities of a composite was studied depending on its composition and functional modification. The composites, characterized by X-ray powder diffraction, Raman, FTIR spectroscopy and scanning electron microscopy, were tested for sorption of selected radionuclides (134Cs+, 85Sr2+) and heavy metals (Pb2+, Cd2+). The dependency on composition was found in connection with a high sorption of Pb2+ and Cd2+. Finally, optimized multifunctional sorbents (Gr-GO-COOH-A in ratio 40:40:20 and Gr:GO:A in ratio 25:25:50) were found to keep interesting high sorption activities for heavy metals and radionuclides with good conductivity properties

Effect of amines on (peroxo)titanates : characterization and thermal decomposition

This report describes the thermal behaviour of nanotitania precursors and the influence of various amines and peroxide treatment on properties of TiO2. Thermal degradation of amine-containing amorphous (peroxo)titanates was examined via TG–DTA coupled with evolved gas analysis (EGA) by mass spectrometry in inert and oxidizing atmosphere. Crystallization to anatase and subsequent transformation to rutile are studied by in situ HT-XRD, which provided information about particle growth and mutual ratio between allotropic phases. In argon, the samples underwent a two-step degradation process, involving the release of moisture and decomposition or evaporation of amine, up to 450 °C, while in air conditions, the organic component could be oxidized in an additional third step at even higher temperatures. EGA confirmed the presence of the original amine in the amino-titanates, while the organic parts reacted with oxygen evolved from the peroxide group to form oxidation products (H2O, CO2 and NOx). The crystallization of nanoanatase began simultaneously/subsequently with the second degradation step. While peroxide treatment increased the initial particle size (from 5 to 40 nm), the choice of amine had a significant impact on the anatase formation temperature (325–425 °C). The anatase particle size increased with higher formation temperature after H2O2 treatment, while the particle size of amino-titanates decreased. The rutile formation temperature was directly dependent on the anatase particle size. Hitherto prepared amine-treated (peroxo)titanates demonstrated good thermal endurance of anatase nanoparticles (800–900 °C), which could be advantageous for various photocatalytic applications. The obtained results provide a method to synthetize tailored TiO2 with desired properties by adjusting the synthetic conditions (selection of precipitation agent and peroxide treatment) and annealing temperatures

A Study of Methylene Blue Dye Interaction and Adsorption by Monolayer Graphene Oxide

The graphene oxide (GO) interaction with methylene blue (MB) cationic dye was studied in an aqueous solution at different pH during MB adsorption. The mutual interaction of MB with GO surface was studied and evaluated by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The π-π and electrostatic interaction of MB with GO surface are the main types of interactions, and the XRD data show the monomeric arrangement of MB cation with GO. The GO surface functional groups and point of zero charge (PZC) were determined by acid-base titration. Suitability of zeta-potential measurement and acid-base titration method was briefly discussed. The quality of prepared GO was evaluated by Raman spectroscopy, XRD, and atomic force microscope (AFM). The experimental adsorption equilibrium data were analyzed using Langmuir, Langmuir-Freundlich, Freundlich, and Temkin isotherms. The GO maximum adsorption capacity increases with higher pH, that is ascribed to the facile interaction of negatively charged GO with positively charged MB structure

Polyhedral oligomeric silsesquioxane-supported ionic liquid for designing nanostructured hybrid organic-inorganic networks

International audienc

Influence of ionic liquid-modified LDH on microwave-assisted polymerization of ε-caprolactone

International audienceThe study reported herein describes multifunctional effect of layered double hydroxide (LDH) modified with phosphonium-based ionic liquids (IL) containing phosphinate, carboxylate and phosphate anions on progress of ring-opening polymerization of ε-caprolactone under microwave irradiation. The extent of IL-modification had a crucial effect on the exfoliation of LDH. The non-modified LDH was able to catalyse the ring-opening polymerization of ε-caprolactone with polymer yield 89% but provided only micro-composite material. On the contrary, LDH with intercalated IL-anions promoted exfoliation of LDH after only 3 min of microwave irradiation. The developed process is fast, environmentally-friendly (solvent-free) and adaptable to various polymer matrices, since a broad variety of IL-anions might be applied

The effects of formation and functionalization of graphene-based membranes on their gas and water vapor permeation properties

The gas and water vapor permeabilities of graphene-based membranes can be affected by the presence of different functional groups directly bound to the graphene network. In this work, one type of carboxylated graphene oxide (GO-COOH) and two types of graphene oxide synthesized i) under strong oxidative conditions directly from graphite (GO-1) and ii) under mild oxidative conditions from exfoliated graphene (GO-2) were used as precursors of self-standing membranes prepared with thicknesses in the range of 12–55 μm via slow-vacuum filtration preparation method. It was observed that the permeabilities for all tested gases decreased in order GO-2 > GO-1 > GO-COOH and depended on both the arrangement of graphene sheets and their functionalization. The GO-1 membrane with a high content of oxygen-containing groups showed the best performance for water vapor permeability. The GO-2 membrane with a thickness of 43 μm exhibited a disordered GO sheet morphology and, therefore, unique gas-separation performance towards H2/CO2 gas pair, showing high hydrogen permeability while keeping extremely high H2/CO2 ideal selectivity that exceeds the Robeson 2008 upper bound of polymer membranes

Ionic Liquids as Delaminating Agents of Layered Double Hydroxide during In-Situ Synthesis of Poly (Butylene Adipate-<i>co</i>-Terephthalate) Nanocomposites

Currently, highly demanded biodegradable or bio-sourced plastics exhibit inherent drawbacks due to their limited processability and end-use properties (barrier, mechanical, etc.). To overcome all of these shortcomings, the incorporation of lamellar inorganic particles, such as layered double hydroxides (LDH) seems to be appropriate. However, LDH delamination and homogenous dispersion in a polymer matrix without use of harmful solvents, remains a challenging issue, which explains why LDH-based polymer nanocomposites have not been scaled-up yet. In this work, LDH with intercalated ionic liquid (IL) anions were synthesized by a direct co-precipitation method in the presence of phosphonium IL and subsequently used as functional nanofillers for in-situ preparation of poly (butylene adipate-co-terephthalate) (PBAT) nanocomposites. The intercalated IL-anions promoted LDH swelling in monomers and LDH delamination during the course of in-situ polycondensation, which led to the production of PBAT/LDH nanocomposites with intercalated and exfoliated morphology containing well-dispersed LDH nanoplatelets. The prepared nanocomposite films showed improved water vapor permeability and mechanical properties and slightly increased crystallization degree and therefore can be considered excellent candidates for food packaging applications