Search Results (14)

The swift recombination of photo-induced electrons and holes is a major obstacle to the catalytic efficiency of TiO₂ nanomaterials, but the incorporation of graphene oxide and out-field modification is considered a potent method to augment photocatalytic properties. In this work, a series of GO/TiO₂ photocatalysts were successfully optimized by a microwave field. As determined by transient photocurrent response and electrochemical impedance spectroscopy (EIS) tests, microwave irradiation at 600 W for 5 min on the GO/TiO₂ photocatalyst promoted interfacial charge transfer and suppressed charge recombination. Through systematic characterizations, GT(600/5) exhibited the highest photooxidation rate (81.5%, 60 min) of Rhodamine B under visible light compared to other homologous samples, owing to the minimum grain size (16.914 nm), enlarged specific surface area (151 m²/g), maximum light response wavelength (510 nm), narrowest bandgap width (2.90 eV), and stronger oxidized hydroxyl radicals (•OH). Given the environmental friendliness, greenness, and sustainability, this study could present an efficient and economical strategy for synthesizing and fine-tuning photocatalysts. Full article

In recent years, graphene oxide (GO)-based two-dimensional (2D) laminar membranes have attracted considerable attention because of their unique well-defined nanochannels and deliver a wide range of molecular separation properties and fundamentals. However, the practical application of 2D GO layered membranes suffers from instability in aqueous solutions as the interlayer d-spacing of GO membranes is prone to expansion caused by the hydration effect. In this study, the effects of the ethylenediamine (EDA) addition amount on the structure, crosslinking mechanism and separation performance of GO membranes were investigated systematically, and membrane performance was evaluated using water permeability and dye/salt rejection tests. The experimental results show that the amine groups of EDA chemically bond with the hydroxyl functional group (O=C–OH) of GO after intercalation, as evident from Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). By further controlling the amount of the intercalated EDA, the as-prepared GO composite membranes show nanoscale-tuned d-spacing promising for downstream applications. In the demonstrated dye/salt nanofiltration scenario, the EDA intercalated and crosslinked GO membrane has enhanced permeability by over five times and a better dye rejection rate of over 96% compared with pure GO membranes. These findings highlight a facile strategy for controlling nanochannels by tuning the amounts of reactive intercalants. Full article

Since the energetic material 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) has potential safety hazards during its application, it was chosen to solve this problem by coating the surface of HMX through the self-polymerization reaction of methyl methacrylate (MMA). However, its mechanical properties were poor for further application, so graphene oxide (GO), hydroxylated graphene (GO_-OH), and reduced graphene oxide (rGO) were chosen to be doped into PMMA for coating modification. The properties were also investigated. The composite microspheres were regular in shape. Furthermore, it was observed that graphene materials were present on the surface of the microspheres, and no crystal transformation of HMX occurred during the process. The thermal stability of the composite microspheres was improved, and the activation energies of the HMX/PMMA/GO, HMX/PMMA/rGO and HMX/PMMA/GO_-OH composite microspheres were increased compared with those of the HMX/PMMA microspheres. At the same time, the high-energy dropout characteristics of the composite microspheres were improved, and the impact sensitivity of all microspheres was reduced, compared with that of the HMX/PMMA microspheres. The compressive strength of pillars pressed with composite microspheres increased by 1.91, 0.92 and 3.13 MPa, respectively. The mechanical properties of the composite microspheres were improved. As a result, HMX/PMMA composite microspheres have better properties. Full article

The utilization of membranes has been extensively employed in the treatment of water and wastewater. Membrane fouling, attributed to the hydrophobic nature of membranes, constitutes a noteworthy concern in the realm of membrane separation. The mitigation of fouling can be achieved through the modification of membrane characteristics, including but not limited to hydrophilicity, morphology, and selectivity. In this study, a nanohybrid polysulfone (PSf) membrane embedded with silver–graphene oxide (Ag-GO) was fabricated to overcome problems related to biofouling. The embedment of Ag-GO nanoparticles (NPs) is the aim towards producing membranes with antimicrobial properties. The fabricated membranes at different compositions of NPs (0 wt%, 0.3 wt%, 0.5 wt%, and 0.8 wt%) are denoted as M0, M1, M2, and M3, respectively. These PSf/Ag-GO membranes were characterized using FTIR, water contact angle (WCA) goniometer, FESEM, and salt rejection. The additions of GO significantly improved the hydrophilicity of PSf membranes. An additional OH peak at 3380.84 cm⁻¹ of the nanohybrid membrane from FTIR spectra may be related to hydroxyl (-OH) groups of GO. The WCA of the fabricated membranes decreased from 69.92° to 54.71°, which confirmed the improvement in its hydrophilicity. In comparison to the pure PSf membrane, the morphology of the finger-like structure of the fabricated nanohybrid membrane slightly bent with a larger bottom part. Among the fabricated membranes, M2 achieved the highest iron (Fe) removal, up to 93%. This finding proved that the addition of 0.5 wt% Ag-GO NPs enhanced the membrane water permeability together with its performance of ionic solute removal (Fe²⁺) from synthetic groundwater. In conclusion, embedding a small amount of Ag-GO NPs successfully improved the hydrophilicity of PSf membranes and was able to achieve high removal of Fe at 10–100 mg L⁻¹ towards purification of groundwater for safe drinking water. Full article

The development of new synthetic methods for methanol-tolerant catalysts with improved performance is of fundamental importance for the commercialization of fuel cells. Herein, we reported a facile displacement reaction-assisted synthesis of graphene-supported sub-nanometer Pt/Bi catalysts (Pt/Bi/rGO). Bismuth (0) nanoparticles produced by NH₃BH₃ reduction can be further dissolved into the ethylene glycol, implying Bi(0) has a strong interaction with the hydroxyl group. That is the key interaction between Bi(0) and the functional group on the rGO to form the ultra-small Bi/rGO catalyst. Furthermore, Pt clusters are obtained by the displacement between Bi(0) and HPtCl₄ and are directly anchored to the rGO surface. The as-synthesized Pt/Bi/rGO catalyst exhibits high oxygen reduction mass activity and high tolerance to methanol poisoning. In the presence of 0.5 mol/L CH₃OH, the initial potential and activity of ORR were almost unchanged, which demonstrated great potential in the application of direct methanol fuel cells. Full article

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a microbial biodegradable polymer with a broad range of promising industrial applications. The effect of incorporation of low amounts (1% w/w) of carbon nanomaterials (CBNs) such as 1D carbon nanofibers (CNFs) or 2D graphene oxide (GO) nanosheets into the PHBV polymer matrix affects its degradation properties, as it is reported here for the first time. The study was performed in simulated gut conditions using two different media: an acidic aqueous medium (pH 6) and Gifu anaerobic medium. The results of this study showed that the incorporation of low amounts of filamentous 1D hydrophobic CNFs significantly increased the degradability of the hydrophobic PHBV after 3 months in simulated intestinal conditions as confirmed by weight loss (~20.5% w/w in acidic medium) and electron microscopy. We can attribute these results to the fact that the long hydrophobic carbon nanochannels created in the PHBV matrix with the incorporation of the CNFs allowed the degradation medium to penetrate at ultrafast diffusion speed increasing the area exposed to degradation. However, the hydrogen bonds formed between the 2D hydrophilic GO nanosheets and the hydrophobic PHBV polymer chains produced a homogeneous composite structure that exhibits lower degradation (weight loss of ~4.5% w/w after three months in acidic aqueous medium). Moreover, the water molecules present in both degradation media can be linked to the hydroxyl (-OH) and carboxyl (-COOH) groups present on the basal planes and at the edges of the GO nanosheets, reducing their degradation potential. Full article

Dielectric materials with excellent thermally conductive and mechanical properties can enable disruptive performance enhancement in the areas of advanced electronics and high-power devices. However, simultaneously achieving high thermal conductivity and mechanical strength for a single material remains a challenge. Herein, we report a new strategy for preparing mechanically strong and thermally conductive composite films by combining aramid nanofibers (ANFs) with graphene oxide (GO) and edge-hydroxylated boron nitride nanosheet (BNNS-OH) via a vacuum-assisted filtration and hot-pressing technique. The obtained ANF/GO/BNNS film exhibits an ultrahigh in-plane thermal conductivity of 33.4 Wm⁻¹ K⁻¹ at the loading of 10 wt.% GO and 50 wt.% BNNS-OH, which is 2080% higher than that of pure ANF film. The exceptional thermal conductivity results from the biomimetic nacreous “brick-and-mortar” layered structure of the composite film, in which favorable contacting and overlapping between the BNNS-OH and GO is generated, resulting in tightly packed thermal conduction networks. In addition, an outstanding tensile strength of 93.3 MPa is achieved for the composite film, owing to the special biomimetic nacreous structure as well as the strong π−π interactions and extensive hydrogen bonding between the GO and ANFs framework. Meanwhile, the obtained composite film displays excellent thermostability (T_d = 555 °C, T_g > 400 °C) and electrical insulation (4.2 × 10¹⁴ Ω·cm). We believe that these findings shed some light on the design and fabrication of multifunctional materials for thermal management applications. Full article

Graphene is a two-dimensional material, with exceptional mechanical, electrical, and thermal properties. Graphene-based materials are, therefore, excellent candidates for use in nanocomposites. We investigated reduced graphene oxide (rGO), which is produced easily by oxidizing and exfoliating graphite in calcium silicate hydrate (CSHs) composites, for use in cementitious materials. The density functional theory was used to study the binding of moieties, on the rGO surface (e.g., hydroxyl-OH/rGO and epoxide/rGO groups), to CSH units, such as silicate tetrahedra, calcium ions, and OH groups. The simulations indicate complex interactions between OH/rGO and silicate tetrahedra, involving condensation reactions and selective repairing of the rGO lattice to reform pristine graphene. The condensation reactions even occurred in the presence of calcium ions and hydroxyl groups. In contrast, rGO/CSH interactions remained close to the initial structural models of the epoxy rGO surface. The simulations indicate that specific CSHs, containing rGO with different interfacial topologies, can be manufactured using coatings of either epoxide or hydroxyl groups. The results fill a knowledge gap, by establishing a connection between the chemical compositions of CSH units and rGO, and confirm that a wet chemical method can be used to produce pristine graphene by removing hydroxyl defects from rGO. Full article

Plastic photodegradation naturally takes 300–500 years, and their chemical degradation typically needs additional energy or causes secondary pollution. The main components of global plastic are polymers. Hence, new technologies are urgently required for the effective decomposition of the polymers in natural environments, which lays the foundation for this study on future plastic degradation. This study synthesizes the in-situ growth of TiO₂ at graphene oxide (GO) matrix to form the TiO₂@GO photocatalyst, and studies its application in conjugated polymers’ photodegradation. The photodegradation process could be probed by UV-vis absorption originating from the conjugated backbone of polymers. We have found that the complete decomposition of various polymers in a natural environment by employing the photocatalyst TiO₂@GO within 12 days. It is obvious that the TiO₂@GO shows a higher photocatalyst activity than the TiO₂, due to the higher crystallinity morphology and smaller size of TiO₂, and the faster transmission of photogenerated electrons from TiO₂ to GO. The stronger fluorescence (FL) intensity of TiO₂@GO compared to TiO₂ at the terephthalic acid aqueous solution indicates that more hydroxyl radicals (•OH) are produced for TiO₂@GO. This further confirms that the GO could effectively decrease the generation of recombination centers, enhance the separation efficiency of photoinduced electrons and holes, and increase the photocatalytic activity of TiO₂@GO. This work establishes the underlying basic mechanism of polymers photodegradation, which might open new avenues for simultaneously addressing the white pollution crisis in a natural environment. Full article

In this study, we have successfully prepared a free-standing Si/void/rGO yolk–shell structured electrode via the electrostatic self-assembly using protonated chitosan. When graphene oxide (GO) is dispersed in water, its carboxyl and hydroxyl groups on the surface are ionized, resulting in the high electronegativity of GO. Meanwhile, chitosan monomer contains -NH₂ and -OH groups, forming highly electropositive protonated chitosan in acidic medium. During the electrostatic interaction between GO and chitosan, which results in a rapid coagulation phenomenon, Si/SiO₂ nanoparticles dispersed in GO can be uniformly encapsulated between GO sheets. The free-standing Si/void/rGO film can be obtained by freeze-drying, high-pressure compression, thermal reduction and HF etching technology. Our investigation shows that after 200 charge/discharge cycles at the current density of 200 mA·g⁻¹, the specific discharge capacity of the free-standing electrode remains at 1129.2 mAh·g⁻¹. When the current density is increased to 4000 mA·g⁻¹, the electrode still has a specific capacity of 469.2 mAh·g⁻¹, showing good rate performance. This free-standing electrode with a yolk–shell structure shows potential applications in the field of flexible lithium-ion batteries. Full article

The influence of the lateral size and the content of graphene oxide (GO) flakes in specific oxygenate functional groups on the anti-biofouling properties and performance of thin-film composite membrane (TFC) was studied. Three different multidimensional GO samples were prepared with small (500–1200 nm), medium (1200–2300 nm), and large (2300–3600 nm) size distribution, and with different degrees of oxidation (GO3 > GO2 > GO1), varying the concentration of the hydrogen peroxide amount during GO synthesis. GO1 sheets’ length have a heterogeneous size distribution containing all size groups, whilst GO2 is contained in a medium-size group, and GO3 is totally contained within a small-size group. Moreover, GO oxygenate groups were controlled. GO2 and GO3 have hydroxyl and epoxy groups at the basal plane of their sheets. Meanwhile, GO1 presented only hydroxyl groups. GO sheets were incorporated into the polyamide (PA) layer of the TFC membrane during the interfacial polymerization reaction. The incorporation of GO1 produced a modified membrane with excellent bactericidal properties and anti-adhesion capacity, as well as superior desalination performance with high water flow (133% as compared with the unmodified membrane). For GO2 and GO3, despite the significant anti-biofouling effect, a detrimental impact on desalination performance was observed. The high content of large sheets in GO2 and small sheet stacking in GO3 produced an unfavorable impact on the water flow. Therefore, the synergistic effect due to the presence of large- and small-sized GO sheets and high content of OH-functional groups (GO1) made it possible to balance the performance of the membrane. Full article

Zirconium hydroxide, Zr(OH)₄ is known to be highly effective for the degradation of chemical nerve agents. Due to the strong interaction force between Zr(OH)₄ and the adsorbed water, however, Zr(OH)₄ rapidly loses its activity for nerve agents under high-humidity environments, limiting real-world applications. Here, we report a nanocomposite material of Zr(OH)₄ and graphene oxide (GO) which showed enhanced stability in humid environments. Zr(OH)₄/GO nanocomposite was prepared via a dropwise method, resulting in a well-dispersed and embedded GO in Zr(OH)₄ nanocomposite. The nitrogen (N₂) isotherm analysis showed that the pore structure of Zr(OH)₄/GO nanocomposite is heterogeneous, and its meso-porosity increased from 0.050 to 0.251 cm³/g, compared with pristine Zr(OH)₄ prepared. Notably, the composite material showed a better performance for nerve agent soman (GD) degradation hydrolysis under high-humidity air conditions (80% relative humidity) and even in aqueous solution. The soman (GD) degradation by the nanocomposite follows the catalytic reaction with a first-order half-life of 60 min. Water adsorption isotherm analysis and diffuse reflectance infrared Fourier transform (DRIFT) spectra provide direct evidence that the interaction between Zr(OH)₄ and the adsorbed water is reduced in Zr(OH)₄/GO nanocomposite, indicating that the active sites of Zr(OH)₄ for the soman (GD) degradation, such as surface hydroxyl groups are almost available even in high-humidity environments. Full article

The effect of NaOH solution on the formation of nanoparticles has been the subject of ongoing debate in selenium-based material research. In this project, the robust correlation between the mechanistic growth of zinc selenide/graphene oxide (ZnSe/GO) composite and the concentration of NaOH are elucidated. The ZnSe/GO composite was synthesized via microwave-assisted hydrothermal method and the concentrations of NaOH are controlled at 2 M, 3 M, 4 M, 5 M and 6 M. The XRD spectra show that the crystal phases of the samples exhibited a 100% purity of ZnSe when the concentration of sodium hydroxide (NaOH) was set at 4 M. The further increase of NaOH concentration leads to the formation of impurities. This result reflects the essential role of hydroxyl ions in modifying the purity state of ZnSe/GO composite. The optical band gap energy of ZnSe/GO composite also decreased from 2.68 eV to 2.64 eV when the concentration of NaOH increased from 2 M to 4 M. Therefore, it can be concluded that the optimum concentration of NaOH used in synthesizing ZnSe/GO composite is 4 M. This project provides an alternative green method in the formation of a high purity ZnSe/GO composite. Full article

Graphene oxide/poly(amidoamine) (GO/PAMAM) nanocomposite adsorbed high quantities of congo red (CR) anionic dye in 0.1 M NaCl solution, with the maximum adsorption capacity of 198 mg·g⁻¹. The kinetics and thermodynamics of adsorption were investigated to elucidate the effects of pH, temperature, shaking rate, ionic strength, and contact time. Kinetic data were analyzed by the KASRA model and the KASRA, ISO, and pore-diffusion equations. Adsorption adsorption isotherms were studied by the ARIAN model and the Henry, Langmuir, and Temkin equations. It was shown that adsorption sites of GO/PAMAM at experimental conditions were phenolic hydroxyl groups of GO sheets and terminal amine groups of PAMAM dendrimer. Analysis of kinetic data indicated that amine sites were located on the surface, and that hydroxyl sites were placed in the pores of adsorbent. CR molecules interacted with the adsorption sites via hydrogen bonds. The molecules were adsorbed firstly on the amine sites, and then on the internal hydroxyl sites. Adsorption kinetic parameters indicated that the interaction of CR to the –NH₃⁺ sites was the rate-controlling step of adsorption of CR on this site and adsorption activation energies calculated for different parts of this step. On the other hand, kinetic parameters showed that the intraparticle diffusion was the rate-controlling step during the interaction of CR molecules to –OH sites and activation energy of this step was not calculable. Finally, the used GO/PAMAM was completely regenerated by using ethylenediamine. Full article