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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.

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.

The aim of this study was to explore the influence of various n-propylamines (mono, di, and tri) and tert-butylamine on the properties of prepared peroxo-titanates and annealed TiO2. Detailed structural characterization (SEM, TEM with EDX, XRD) confirmed the 2D-foil morphology of TiO2 nanocrystals and the CHNS analysis together with XPS showed presence of carbon (under 1 wt%). The annealed TiO2 showed excellent photocatalytic activity and up to four times higher decomposition rate constant upon UV irradiation than the P25. Favourable growth of TiO2 crystals was observed especially when propylamine and tert-butylamine were used (as precursors for the peroxo-titanates). Increased photocatalytic efficiency of the highly crystalline nano-TiO2 was confirmed due to high-reactive anatase facets and the morphology composed of microsheets formed by interconnected nanocrystals. The photoinduced electron transfer was confirmed via EPR spectroscopy. This synthesis’ procedure offers a novel preparation method of highly photoactive C-doped TiO2 achieved relatively easily after annealing of lyophilized amino-peroxo-titanate.

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.

Titanium dioxide (TiO2) is used as a UV light absorber to protect wood matter from photodegradation. In this paper, interactions between wood and TiO2 coating are studied, and the efficiency of the coating is evaluated. For the experiments, two wood species were chosen: beech (Fagus sylvatica) and pine (Pinus sylvestris). Molecular and physical modifications in coated and uncoated wood exposed to UV radiation were investigated with Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) and transmission electron microscopy (TEM). UV-VIS spectroscopy was used to describe the absorption of UV light by the TiO2 planar particles chosen for the experiment. It was demonstrated that TiO2 coating protects wood against photodegradation to a limited extent. TEM micrographs showed fissures in the wood matter around clusters of TiO2 particles in beech wood.

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.

The reaction of the arylphosphonic acid esters 4,4′-[(i-PrO)2P(O)]C6H4C6H4[P(O)(Oi-Pr)2] (L1), 1,3,5-[(i-PrO)2P(O)]3C6H3 (L2), and 5-t-Bu-1,3-[(i-PrO)2P(O)]2C6H3 (L3), respectively, with bismuth halides BiX3 (X=Cl, Br, I) gave seven novel bismuth coordination polymers that have been characterized by single-crystal X-ray diffraction analysis. The solid-state structures of [(BiCl3)(L1)] (1), [(BiBr3)(L1)]·0.25CH3CN (2·0.25CH3CN), [(BiI3)2(L1)]·0.25CH3CN (3·0.25CH3CN), [(BiCl3)(L2)] (4), [(BiCl3)2(L2)] (5), [(BiBr3)2 (L2)]·CH3CN (6·CH3CN), and [(BiCl3)(L3)] (7) are presented. Thermal analysis of [(BiCl3)2(L2)] (5) is indicative of a conversion of the complexes into a bismuth phosphonate by complete i-PrX elimination, whereas for [(BiBr3)2(L2)] (6), elimination of i-PrBr and BiBr3 is assumed. Compounds 1–3 form one-dimensional coordination polymers, whereas two-dimensional networks are observed for compounds 4–7.

Huntington's disease (HD) is an autosomal dominant disease affecting neurons predominantly in the striatum due to the production of the toxic huntingtin protein. Lowering the concentration of mutant huntingtin is a promising therapeutic approach, and a suitable delivery system is fascinating. Nanoparticles (NPs) minimize the host immune response and have no limit concerning the number of NPs administered. They are safe, targeted, and effective for RNA therapeutics providing a significant mode to cross the blood–brain barrier for a broad range of clinical applications. The present study generated and characterized magnetic NPs (MNPs) using the co-precipitation method with a mean particle size of around 10–20 nm. The dynamic light scattering and zeta potential measurements showed that NPs exhibited narrow size distribution and sufficient colloidal stability. These oleic acid-coated MNPs were further cross-linked with polyethyleneimine and designed to deliver interfering RNA into human embryonic kidney cells (HEK-293) driven by an external magnetic field. These MNPs showed low cytotoxicity with high transfection efficiency. Furthermore, a transient downregulation was observed in endogenous huntingtin protein obtained by RT-PCR and Western blot analysis. Thus, these MNPs may represent a promising and efficient platform for siRNA delivery and provide a potential treatment strategy for HD. [ABSTRACT FROM AUTHOR]

The aim of this study was to explore the influence of various n-propylamines (mono, di, and tri) and tert -butylamine on the properties of prepared peroxo-titanates and annealed TiO 2. Detailed structural characterization (SEM, TEM with EDX, XRD) confirmed the 2D-foil morphology of TiO 2 nanocrystals and the CHNS analysis together with XPS showed presence of carbon (under 1 wt%). The annealed TiO 2 showed excellent photocatalytic activity and up to four times higher decomposition rate constant upon UV irradiation than the P25. Favourable growth of TiO 2 crystals was observed especially when propylamine and tert -butylamine were used (as precursors for the peroxo-titanates). Increased photocatalytic efficiency of the highly crystalline nano-TiO 2 was confirmed due to high-reactive anatase facets and the morphology composed of microsheets formed by interconnected nanocrystals. The photoinduced electron transfer was confirmed via EPR spectroscopy. This synthesis' procedure offers a novel preparation method of highly photoactive C-doped TiO 2 achieved relatively easily after annealing of lyophilized amino-peroxo-titanate. [ABSTRACT FROM AUTHOR]

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 H 2 /CO 2 gas pair, showing high hydrogen permeability while keeping extremely high H 2 /CO 2 ideal selectivity that exceeds the Robeson 2008 upper bound of polymer membranes., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors.)

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 ( 134 Cs + , 85 Sr 2+ ) and heavy metals (Pb 2+ , Cd 2+ ). The dependency on composition was found in connection with a high sorption of Pb 2+ and Cd 2+ . 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., Competing Interests: The authors declare no competing interests., (© 2022 The Author(s).)

Titanium dioxide (TiO 2 ) is used as a UV light absorber to protect wood matter from photodegradation. In this paper, interactions between wood and TiO 2 coating are studied, and the efficiency of the coating is evaluated. For the experiments, two wood species were chosen: beech ( Fagus sylvatica ) and pine ( Pinus sylvestris ). Molecular and physical modifications in coated and uncoated wood exposed to UV radiation were investigated with Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) and transmission electron microscopy (TEM). UV-VIS spectroscopy was used to describe the absorption of UV light by the TiO 2 planar particles chosen for the experiment. It was demonstrated that TiO 2 coating protects wood against photodegradation to a limited extent. TEM micrographs showed fissures in the wood matter around clusters of TiO 2 particles in beech wood.

The carbon nanomaterials and congeners, e.g., graphene or graphene oxide (GO), dispose of numerous unique properties, which are not necessarily intrinsic but might be related to a content of impurities. The oxidation step of GO synthesis introduces a considerable amount of metallic species. Therefore, large-scale purification is an actual scientific challenge. Here we describe new purification technique (salt‑washing), which is based on three consecutive steps: (a) aggregation of GO sheets with NaCl (b) washing of the aggregates and (c) removing of the salt to afford purified GO (swGO). The considerably improved purity of swGO was demonstrated by ICP and EPR spectroscopy. The microscopic methods (TEM with SEAD, AFM) proved that the salt-washing does not affect the morphology or concentration of defects, showing the aggregation of GO with NaCl is fully reversible. The eligibility of swGO for biomedical applications was tested using fibroblastic cell cultures. The determined IC 50 values clearly show a strong correlation between the purity of samples and cytotoxicity. Although the purification decreases cytotoxicity of GO, the IC 50 values are still low proving that cytotoxic effect is not only impurities-related but also an intrinsic property. These findings may represent a serious limitation for usage of GO in biomedical applications., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Herein we describe a successful protocol for graphite exfoliation using a biphasic liquid system (water/dichloromethane, DCM) containing ionic liquids (ILs; 1,3-dibenzylimidazolium benzoate- and 1-naphthoate). The use of (surface active) IL and sonication led to stable DCM/water (O/W) emulsion, which enhanced graphene formation, suppressed its re-aggregation and decreased shear/cavitation damage. The O/W emulsion stabilization by the ILs was studied by dynamic light scattering (DLS), whereas their interaction with the graphene sheets were described by Density Functional Theory (DFT) calculations. Moreover, a comprehensive investigation on cavitation-based exfoliation in the O/W systems was performed to assess the importance of operational parameters, including, the type of ultrasound processor, ultrasound power and insonation, and the influence of the exfoliation medium., (Copyright © 2019 Elsevier B.V. All rights reserved.)

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.

Design and synthesis of ordered, metal-free layered materials is intrinsically difficult due to the limitations of vapor deposition processes that are used in their making. Mixed-dimensional (2D/3D) metal-free van der Waals (vdW) heterostructures based on triazine (C 3 N 3 ) linkers grow as large area, transparent yellow-orange membranes on copper surfaces from solution. The membranes have an indirect band gap (E g,opt = 1.91 eV, E g,elec = 1.84 eV) and are moderately porous (124 m 2 g -1 ). The material consists of a crystalline 2D phase that is fully sp 2 hybridized and provides structural stability, and an amorphous, porous phase with mixed sp 2 -sp hybridization. Interestingly, this 2D/3D vdW heterostructure grows in a twinned mechanism from a one-pot reaction mixture: unprecedented for metal-free frameworks and a direct consequence of on-catalyst synthesis. Thanks to the efficient type I heterojunction, electron transfer processes are fundamentally improved and hence, the material is capable of metal-free, light-induced hydrogen evolution from water without the need for a noble metal cocatalyst (34 µmol h -1 g -1 without Pt). The results highlight that twinned growth mechanisms are observed in the realm of "wet" chemistry, and that they can be used to fabricate otherwise challenging 2D/3D vdW heterostructures with composite properties., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We present a new, simple, quick and ecologically friendly method of exfoliating graphite to produce graphene. The method is based on the intercalation of a permanganate M2MnO4 (M=K, Na, Li), which is formed by the reaction of a manganate MMnO4 with an alkali metal hydroxide MOH. The quality of exfoliation and the morphology were determined using X-ray photoelectron spectroscopy, X-ray diffraction and microscopic techniques, including transmission electron microscopy and atomic force microscopy. We observed that a stable graphene suspension could be prepared under strongly alkaline conditions in the presence of permanganate and ultrasound assistance. The use of only an alkaline environment for the direct preparation of graphene from graphite structures has not been previously described or applied. It was found that such a method of preparation leads to surprisingly high yields and a stable product for hydrophilic graphene applications., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Although they decompose rapidly to produce cyanocarbenes, ethynyl azides were generated from (chloroethynyl)arenes and trapped for the first time by 1,3-dipolar cycloaddition at cyclooctyne.