A selection guide for efficient graphene oxide-composite adsorbents

The performance of graphene oxide (GO) based nanofiltration membranes is strongly influenced by their interlayer spacing, governed by two competing factors: GO swelling in the liquid phase and penetrant adsorption. In this work, the structure of GO membranes was optimized via H2O2 treatment, and their performance was evaluated during nanofiltration of cationic and anionic dyes. For anionic dyes, the permeate flux remained stable, whereas cationic dyes caused a significant and irreversible flux decline. To clarify this behavior, dye adsorption experiments and in situ diffraction analyses of the GO interlayer distance were performed. The highest adsorption capacity was recorded for cationic methylene blue (MnB) at 643 mg g-1 (GO), compared to 97 mg g-1 (GO) for anionic methyl orange (MO). In the case of MO, the occupation of the interlayer space by dye molecules was compensated by slight structural expansion, maintaining flux stability. Conversely, the filtration of even a small amount of MnB solution caused a reduction in d-spacing from 12.1 ± 0.1 Å to 11.7 ± 0.1 Å, followed by further shrinkage to 11.4 ± 0.1 Å due to the electrostatic compression of the negatively charged GO with the positively charged dye molecules. Combined with physical blockage by dye molecules, this led to a rapid decline in membrane permeance described well by Poiseuille-based permeance trends. These results show that adsorption, particularly at low penetrant concentrations, can affect measured rejection rates and that adsorption can substantially alter the membrane permeance. Considering the roles of adsorption and electrostatic interactions, charged dyes are unsuitable for permeation tests intended to assess the intrinsic size-exclusion properties of two-dimensional lamellar membranes.

Improved strength and toughness of semi-aromatic polyamide 6T-co-6(PA6T/6)/GO composites via in situ polymerization

The poly(butylene succinate) (PBS)/graphene oxide (GO) composites containing different GO contents were prepared. The dispersion of GO was investigated using optical microscope (OM), scanning electron microscope (SEM), and transmission electron microscope (TEM). The results showed that GO exhibited good dispersion in the polar PBS matrix. The rheological measurements showed that the presence of GO induced largely increased melt viscosity for the composites. Specifically, high content of GO formed the percolated network structure. The non-isothermal crystallization kinetics was investigated using differential scanning calorimetry. The results showed that the non-isothermal crystallization behavior of PBS was influenced by GO content and cooling rate. At relatively small content, GO dramatically accelerated the crystallization of PBS. More integrated PBS crystalline structure was achieved by introducing GO. The nucleation effect of GO in the composites was proved further by the variation of isothermal crystallization morphologies.

Spindle-shaped microstructure of α-Fe2O3 was successfully synthesized by a simple hydrothermal method. The α-Fe2O3/graphene oxide (GO) composites was prepared using a modified Hummers’ strategy. The properties of the samples were systematically investigated by X-ray powder diffraction (XRD), UV–Vis diffuse reflectance spectrophotometer, transmission electron microscope, atomic force microscope, X-ray photoelectron spectroscopy, and Raman spectroscopy (Raman) techniques. GO nanosheets act as supporting materials for anchoring the α-Fe2O3 particles. The average crystallite sizes of the α-Fe2O3 and α-Fe2O3/GO samples are ca. 27 and 24 nm, respectively. The possible growth of α-Fe2O3 onto GO layers led to a higher absorbance capacity for visible light by α-Fe2O3/GO than α-Fe2O3 composite. The photocatalytic degradation of toluene over the α-Fe2O3 and α-Fe2O3/GO samples under xenon-lamp irradiation was comparatively studied by in situ FTIR technique. The results indicate that the α-Fe2O3/GO sample synthesized exhibited a higher capacity for the degradation of toluene. The composite of α-Fe2O3/GO could be promisingly applied in photo-driven air purification.

Improved room-temperature hydrogen storage performance of lithium-doped MIL-100(Fe)/graphene oxide (GO) composite

Using silicon/reduced graphene oxide (Si/rGO) composites as lithium-ion battery (LIB) anodes can effectively buffer the volumetric expansion and shrinkage of Si. Herein, we designed and prepared Si/rGO-b with a sandwiched structure, formed by a duple combination of ammonia-modified silicon (m-Si) nanoparticles (NP) with graphene oxide (GO). In the first composite process of m-Si and GO, a core-shell structure of primal Si/rGO-b (p-Si/rGO-b) was formed. The amino groups on the m-Si surface can not only hybridize with the GO surface to fix the Si particles, but also form covalent chemical bonds with the remaining carboxyl groups of rGO to enhance the stability of the composite. During the electrochemical reaction, the oxygen on the m-Si surface reacts with lithium ions (Li+) to form Li2O, which is a component of the solid-electrolyte interphase (SEI) and is beneficial to buffering the volume expansion of Si. Then, the p-Si/rGO-b recombines with GO again to finally form a sandwiched structure of Si/rGO-b. Covalent chemical bonds are formed between the rGO layers to tightly fix the p-Si/rGO-b, and the conductive network formed by the reintroduced rGO improves the conductivity of the Si/rGO-b composite. When used as an electrode, the Si/rGO-b composite exhibits excellent cycling performance (operated stably for more than 800 cycles at a high-capacity retention rate of 82.4%) and a superior rate capability (300 mA h/g at 5 A/g). After cycling, tiny cracks formed in some areas of the electrode surface, with an expansion rate of only 27.4%. The duple combination of rGO and the unique sandwiched structure presented here demonstrate great effectiveness in improving the electrochemical performance of alloy-type anodes.

Metal‐organic frameworks (MOFs) often suffer from poor stability, making them suitable precursors for metal oxides/porous carbon catalysts in the oxygen evolution reaction via pyrolysis. High‐temperature treatment, however, leads to significant loss of active sites. To address this, Fe‐MOFs, FeCo‐MOFs, and FeCo‐MOFs/graphene oxide (GO) composites using a one‐pot hydrothermal method are synthesized and annealed at a low temperature of 300 °C. Characterization reveals that FeCo‐MOFs/GO composites possess unique nanowire structures mixed with a small amount of nanoflakes. It is believed that introducing graphene oxide plays a critical role in forming this structure, because the defects in GO provide numerous nucleation sites for nanowire growth. With high specific surface area and good stability, these nanostructures show a low overpotential of 261.5 mV at a current density of 10 mA cm−2 and a Tafel slope of 20.47 mV dec−1 in 1 mol L−1 KOH alkaline water electrolysis. Density functional theory calculations further indicate that the synergistic effect of Fe and Co atoms enhances the catalytic activity.

Water contamination by heavy metals poses serious risks to human health, ecosystems, and food security. Established and commonly used remediation methods have limitations in terms of cost, sustainability, and environmental impact, especially in under-resourced, developing, and underdeveloped countries. Recently, the emergence of biodegradable polymer blend foams filled with carbonaceous materials, such as graphene oxide and carbon nanotubes, offers environmentally friendly adsorbents for heavy metals in water. However, a consolidated, synthetic overview of the evidence on material design, properties, adsorption capacities, and efficiencies remains lacking for these foams. The current systematic review aims to synthesise and critically evaluate the existing evidence on the fabrication, properties, adsorption mechanisms, and applicability of biodegradable polymer blend foams filled with carbonaceous materials for adsorbing heavy metals in water. The review also seeks to develop a consolidated evidence document that will inform policy, guide future research, and assist the development and implementation of sustainable treatment technologies for the removal of heavy metals in water in resource-limited areas. This systematic review protocol is based on the question, "What is the adsorption efficiency and capacity of biodegradable polymer blend foams filled with carbonaceous materials in the removal of heavy metals from water?" A comprehensive search will be conducted using electronic bibliographic sources like Web of Science (core collections), Scopus, ScienceDirect, and search engines like PubMed, together with grey literature like Google Scholar, targeting peer-reviewed studies on laboratory and pilot-scale investigations of biodegradable polymer blend foams filled with carbonaceous materials for the removal of heavy metals from water. Eligibility criteria include studies on any type of water contaminated with heavy metals such as lead, copper, chromium, and cadmium. The extraction of data will be focused on material composition, processing techniques, characterisation, and adsorption performance. Quantitative data will be tabulated and, where applicable, subjected to meta-analysis. Researchers, consultants, and municipalities - especially in South Africa- will be consulted to contextualise findings and assist in translating evidence into practical water treatment solutions.

Composites based on poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS)—graphene oxide (GO) are increasingly considered for sensing applications. In this work we aim at patterning and prototyping microscale geometries of PEDOT:PSS: GO composites for the modification of commercially available electrochemical sensors. Here, we demonstrate the laser-induced forward transfer of PEDOT:PSS: GO composites, a remarkably simple procedure that allows for the fast and clean transfer of materials with high resolution for a wide range of laser fluences (450–750 mJ/cm2). We show that it is possible to transfer PEDOT:PSS: GO composites at different ratios (i.e., 25:75 %wt and 50:50 %wt) onto flexible screen-printed electrodes. Furthermore, when testing the functionality of the PEDOT:PSS: GO modified electrodes via LIFT, we could see that both the PEDOT:PSS: GO ratio as well as the addition of an intermediate release layer in the LIFT process plays an important role in the electrochemical response. In particular, the ratio of the oxidation peak current to the reduction peak current is almost twice as high for the sensor with a 50:50 %et PEDOT:PSS: GO pixel. This direct transfer methodology provides a path forward for the prototyping and production of polymer: graphene oxide composite based devices.

Preparation and enhanced CO2 adsorption capacity of UiO-66/graphene oxide composites

3-Nitrobenzantrone (3-NBA) is a mutagenic and genotoxic compound, mainly generated during the burning of fossil fuels and that has been found in different environmental matrices. Due to these characteristics, the development of remediation techniques to reduce the 3-NBA environment concentration is extremely necessary. Currently, nanomaterials have been used to remediate organic pollutants present in the water. Among them, graphene oxide (GO) has been used in various applications due to its versatile chemical composition, large surface area and good solubility which allow physical or chemical adsorption of organic pollutants. The aim of this work was to study the capacity of GO to adsorb 3-NBA in water. We used biological tests to determine the GO adsorption capacity, especially the Salmonella/microsome test (Ames test) because the 3-NBA is very powerful in this type of test. Salmonella/microsome tests have shown that GO is really capable of adsorbing 3-NBA. This adsorption is dependent on the amount of GO used in the tests with higher GO concentrations leading to higher 3-NBA adsorption. Chemical processes involving basic washing GO with NaOH solution led to an increase in the adsorption capacity of the GO samples. We suggest that this increase can be attributed to the removal of surface residues from the GO synthesis (known as oxidation debris) and to the partial removal of oxygenated groups present in the GO surface, depending on models used to describe the GO chemical structure.

Synergistic interaction of bacteria with graphene oxide for high performance supercapacitor

Impact of enhanced interfacial strength on physical, mechanical and tribological properties of copper/reduced graphene oxide composites: Microstructural investigation

Quick responding humidity sensor based on polyaniline/reduced graphene oxide composite

Poly(vinyl alcohol)/graphene oxide (PVA/GO) composites were studied by molecular mechanics and molecular dynamics methods to analyze the effect of GO sheet addition on PVA material. The properties ...