Modification of Graphene Oxide with Amphiphilic Double-Crystalline Block Copolymer Polyethylene-b-poly(ethylene oxide) with Assistance of Supercritical CO2 and Its Further Functionalization

Investigating the Reduction/Oxidation Reversibility of Graphene Oxide for Photocatalytic Applications

The aim of the study was to analyze the reversibility of the cycle of graphene oxide (GO), reduced GO, and GO obtained by consecutive reoxidation of reduced GO. Accordingly, GO was heated in three different atmospheres (oxidizing, inert, and reducing, i.e., air, nitrogen, and argon/hydrogen mixture, respectively) at 400 °C to obtain reduced GO with varying composition. The bare GO and the RGO samples were oxidized or reoxidized with HNO₃. The thermal properties, composition, bonds, and structure of the samples were investigated with TG/DTA, EDX, Raman spectroscopy, and XRD. Their photocatalytic activity was tested by decomposing methyl orange dye under UV light irradiation.

Effects of graphene derivatives on polyvinylidene fluoride membrane modification evaluated with XDLVO theory and quartz crystal microbalance with dissipation

In this study, the different graphene derivatives, graphene oxide (GO), carboxylic acid-modified graphene (G-COOH), and amine-modified graphene (G-NH₂ ), were used to prepare polyvinylidene fluoride (PVDF) composite membranes. The membrane modification performance was evaluated using the extended Derjaguin-Landau-Verwey-Overbeek theory and quartz crystal microbalance dissipation monitoring. The results show that the addition of low-dose GO and G-NH₂ can improve membrane surface porosity and permeability. The hydrophilicity and electron donor monopolarity of PVDF/GO composite membranes were enhanced by adding more than 0.024 wt% GO, thus improving its antifouling ability. In addition, the enhancement of hydrophilicity, free energy of cohesion, and antifouling ability of composite membrane modified with G-COOH and G-NH₂ was more significant compared with that of GO with the same dosage, which implies the important role of functional group in additives. This study provides new insights for the blending modification of PVDF membranes by systematically comparing the addition of graphene derivatives with different functional groups. PRACTITIONER POINTS: The comprehensive comparison of membrane modification with different graphene derivatives was investigated. The enhancement of hydrophilicity and antifouling ability of membranes modified with G-COOH and G-NH₂ was more significant than that of GO. The free energy of cohesion of nanocomposite membrane was affected by the functional group of additives. G-NH₂ composite membrane had the best comprehensive performance with great hydrophilicity, permeability, and antifouling performance.

Influence of graphene oxide nanosheets on the cotransport of cu-tetracycline multi-pollutants in saturated porous media

Antibiotic-heavy metal multi-pollutants are produced by intensive livestock farming and become an increasingly prominent problem. In this study, the transport behavior of tetracycline (TC) and its chelate with copper ions (Cu-TC) in saturated sand column with and without graphene oxide (GO) prefilled was investigated by laboratory breakthrough experiments. The effects of pH, ionic strength, and the cotransport with GO were studied detailedly. The results showed that the prepared nano-GO had a single- or multilayered sheet structure with a diameter of several μm. The surface of GO contained abundant oxygen-containing functional groups, which imparted it strong hydrophilicity and electronegativity. Pollutant transport experiments showed that decrease of H⁺ weakened the transport ability of TC and Cu-TC. Both Na⁺ and Ca²⁺ promoted the transport of TC, with Ca²⁺ having a much greater effect. The presence of Na⁺ inhibited the transport of Cu-TC, while Ca²⁺ promoted Cu-TC transport. The addition of Cu²⁺ was more favorable for the transport of Cu-TC than TC alone. In the GO-prefilled column, the effluent concentrations of TC and Cu-TC greatly decreased due to adsorption onto GO surfaces. The transport of Cu-TC was more related to GO concentration than TC alone due to the high affinity between GO and Cu-TC. Moreover, the transport behavior of GO in the sand column was consistent with that of the corresponding TC or Cu-TC, indicating that GO could cotransport with TC and Cu-TC multi-pollutants. Our study showed that the GO would interact with TC and Cu-TC and thus have significant influences on the fate and transport of these pollutions in porous media.

Polyethylene glycol-stabilized nano zero-valent iron supported by biochar for highly efficient removal of Cr(VI)

In this study, polyethylene glycol (PEG)-stabilized nano zero-valent iron (nZVI) supported by biochar (BC) (PEG-nZVI@BC) was prepared to remedy Cr(VI) with high efficiency. The morphology, functional groups, and crystalline structure of PEG-nZVI@BC composites were characterized, revealing that when PEG was added, a large number of -OH functional groups were introduced, and nZVI was effectively dispersed on the BC surface with a smaller particle size. The results of Cr(VI) remediation experiments showed Cr(VI) removal rate by PEG-nZVI@BC (97.38%) was much greater than that by BC-loaded nZVI (nZVI@BC) (51.73%). The pseudo second-order and Sips isotherm models provide the best simulation for Cr(VI) removal experimental data, respectively. The main remediation mechanism of Cr(VI) was reduction and co-precipitation of Cr-containing metal deposits onto PEG-nZVI@BC. Ecotoxicity assessment revealed PEG-nZVI@BC (1.00 g/L) has little influence on rice germination and growth, but resisted the toxicity of Cr(VI) to rice. The modified Community Bureau of Reference (BCR) sequential extraction showed pyrolysis could increase the percentage of oxidizable and residual Cr and diminish the environmental risk of Cr release from post-removal composites.

Supercritical Fluid-Facilitated Exfoliation and Processing of 2D Materials

Since the first intercalation of layered silicates by using supercritical CO2 as a processing medium, considerable efforts have been dedicated to intercalating and exfoliating layered two-dimensional (2D) materials in various supercritical fluids (SCFs) to yield single- and few-layer nanosheets. Here, recent work in this area is highlighted. Motivating factors for enhancing exfoliation efficiency and product quality in SCFs, mechanisms for exfoliation and dispersion in SCFs, as well as general metrics applied to assess quality and processability of exfoliated 2D materials are critically discussed. Further, advances in formation and application of 2D material-based composites with assistance from SCFs are presented. These discussions address chemical transformations accompanying SCF processing such as doping, covalent surface modification, and heterostructure formation. Promising features, challenges, and routes to expanding SCF processing techniques are described.

Organophilic graphene nanosheets as a promising nanofiller for bio-based polyurethane nanocomposites: investigation of the thermal, barrier and mechanical properties

The present study focuses on the design of new nanocomposite films using bio-based thermoplastic polyurethane (TPU) as a polymer matrix and long chain amine functionalized reduced graphene oxide (G-ODA) as a nanofiller.

Epitaxial crystallization of precisely bromine-substituted polyethylene induced by carbon nanotubes and graphene

Epitaxial crystallization of precisely bromine-substituted polyethylene induced by carbon nanotubes and graphene.

Prospects of Supercritical Fluids in Realizing Graphene-Based Functional Materials

Supercritical-fluids science and technology predate all the approaches that are currently established for graphene production by several decades in advanced materials design. However, it has only recently been proposed as a plausible approach for graphene processing. Since then, supercritical fluids have emerged into contention as an alternative to existing technologies because of their scalability and versatility in processing graphene materials, which include composites, aerogels, and foams. Here, an overview is presented of such materials prepared through supercritical fluids from an advanced materials science standpoint, with a discussion on their fundamental properties and technological applications. The benefits of supercritical-fluid processing over conventional liquid-phase processing are presented. The benefits include not only better performances for advanced applications but also environmental issues associated with the synthesis process. Nevertheless, the limitations of supercritical-fluid processing are also stressed, along with challenges that are still faced toward the achievement of the great expectations from graphene materials.

Electrospun Fibers of Enteric Polymer for Controlled Drug Delivery

The production of electrospun fibers of enteric polymer for controlled delivery of drugs represents a simple and low cost procedure with promising advantages relative to the longer therapeutic window provided by cylindrical geometry in association with intrinsic properties of pH-dependent drug carriers. In this work, we have explored the incorporation of additives (block copolymers of poly(ethylene)-b-poly(ethylene oxide)) into matrix of Eudragit L-100 and the effective action of hybrid composites on delivery of nifedipine, providing improvement in the overall process of controlled release of loaded drug.

Coarse-grained molecular simulation of self-assembly for nonionic surfactants on graphene nanostructures

Self-assembly of amphiphilic molecules on the surfaces of nanoscale materials has an important application in a variety of nanotechnology. Here, we report a coarse-grained molecular dynamics simulation on the structure and morphology of the nonionic surfactant, n-alkyl poly(ethylene oxide) (PEO), adsorbed on planar graphene nanostructures. The effects of concentration, surfactant structure, and size of graphene sheet are explored. Because of the finite dimension effect, various morphological hemimicelles can be formed on nanoscale graphene surfaces, which is somewhat different from the self-assembly structures on infinite carbon surfaces. The aggregate morphology is highly dependent on the concentration, the chain lengths, and the size of graphene nanosheets. For the nonionic surfactant, the PEO headgroups show strong dispersion interaction with the carbon surface, leading to a side edge adsorption behavior. This simulation provides insight into the supramolecular self-assembly nanostructures and the adsorption mechanism for the nonionic surfactants aggregated on graphene nanostructures, which could be exploited to guide fabrication of graphene-based nanocomposites.

Synthesis and characterization of amphiphilic reduced graphene oxide with epoxidized methyl oleate

Amphiphilic reduced graphene oxide is obtained by oleo-functionalization with epoxidized methyl oleate (renewable feedstock) using a green process. The excellent diverse solvent-dispersivity of the oleo-reduced amphiphilic graphene and its reduction chemistry are confirmed in this study. Oleo-reduction of amphiphilic graphene is amenable to industrially viable processes to produce future graphene-based polymer composites and systems.