Surface-modified Graphene Oxide Research Articles

Surface strengthening mechanism of graphene-oxide membrane and its modified aluminium lamina under penetration loading

The contact surface is crucial in determining the ability of membranes or laminas to absorb energy during penetration. This study conducted experiments to explore the mechanical properties of the pristine graphene oxide (GO) membrane when dry, as well as the anti-penetration performance of four surface-modified GO membranes (dry, oil, water, and grease) under various loading velocities. Dynamic penetration occurs when the kinetic energy exceeds a specific threshold, as opposed to the quasi-static outcomes. Additionally, the examination of failure mode indicated that the GO membrane demonstrates significant elastic rebound when subjected to comparatively lower levels of dynamic loading. Further analysis after penetration revealed a transition from brittleness to ductility under dynamic loading conditions. Uniaxial tensile tests of aluminium sheets revealed a distinct negative velocity sensitivity behaviour. Moreover, surface treatment with the GO membrane can enhance the penetration failure strength and energy absorption capacity of the sheet. This study provides crucial insights into the physical principles governing the energy absorption of membrane structures and how they are influenced by surface conditions.

Rheological enhancement of fresh polymer-modified cement composites via surface-modified graphene oxide

Polymer-modified cement (PMC) composites are extensively utilized in modern construction, especially in tunneling and structural applications, but their excessive flowability and reduced thixotropy continue to present fundamental rheological challenges. We present a novel approach to improving the rheological performance of PMC via surface-modified graphene oxide (GO), i.e., GOPMC composites. Specifically, the flow behavior of GOPMCs in relation to shear stress–shear strain response and apparent viscosity were investigated. The rheological parameters were analyzed by using Herschel–Bulkley's model. Additionally, zeta potential and dispersion analysis were conducted to investigate interparticle interaction forces. Flow measurement confirmed ∼20 % lower flowability of the GOPMC than the reference PMC. GOPMC composites further displayed higher yield stress of ∼82 % and ∼33 % reduced viscosity with inherent decreased shear-thickening compared to reference PMC composites. The yield stress of the GOPMC composite increased over time, disclosing distinct structural evolution linked to enhanced hydration kinetics by GO. Additionally, GO nanosheets in the GOPMC altered the rheopectic behavior of the redispersible polymer and enhanced the degree of thixotropy by ∼80 %, attributable to the promotion of bridged flocculated structures which produces a rigid system, facilitated by particle interaction forces comprising of van der Waals and steric forces. This latter observation provides a mechanistic framework for the enhanced rheological performance of GOPMC composites aiming at broader civil engineering and construction sector applications beyond tunneling.

Bias-switchable photoconductance in surface-modified graphene oxide by green synthesized ZnO nanoparticles

This study provides an environmentally friendly method for synthesizing Zinc oxide (ZnO) nanoparticles through Adhatoda vasica extracts as plant-mediated reducing agents. ZnO-GO nanostructures are prepared using microwave irradiation, while a modified Hummer's method was employed for graphene oxide (GO) synthesis. The thorough characterization establishes the purity, phase and structural conformation of the synthesized ZnO-GO NCs. The observation of ZnO nanoparticles accumulating over the GO surface through High-Resolution Transmission Electron Microscopy and Scanning Electron Microscopy validates the formation of nanocomposites. The resulting ZnO-GO nanocomposites displayed remarkable and broad photoresponsivity across various wavelengths. Notably, at 480 nm, photoresponsivity is found to be a maximum of 0.47 mA/W, whereas it is 0.29 mA/W and 0.21 mA/W at 520 nm and 670 nm respectively. We have achieved responsiveness of 0.48 µA/W and detectivity of 13.9 × 106 Jones at 480 nm with biasing voltage of 1 nV which reflects their potential for self-biased optoelectronic devices. Thus, the photodetector demonstrates a positive photoresponse within the voltage range of 5–30 volts while exhibiting a negative photoresponse in the range of 1–100 nanovolts. This aspect introduces a novel and unprecedented characteristic to the device's behavior. Overall, the integration of eco-friendly synthesis methods, comprehensive characterization, and device performance puts this work with promising implications for sustainable and advanced technology development.

Injectable and Self-Healable Thermoresponsive Hybrid Hydrogel Constructed via Surface-Modified Graphene Oxide Loading Exosomes for Synergistic Promotion of Schwann Cells

Injectable and Self-Healable Thermoresponsive Hybrid Hydrogel Constructed via Surface-Modified Graphene Oxide Loading Exosomes for Synergistic Promotion of Schwann Cells

Photoresponse of surface modified graphene oxide by green synthesized silver and gold nanoparticles

In the current work, graphene oxide nanocomposites containing silver and gold nanoparticles i.e., Ag-GO and Au-GO, were formed by reducing Ag+ and Au+ cations with black tea extract. The precise reduction of precursors is facilitated by the water-soluble, highly reactive reducing agent referred as tea polyphenols. To confirm the morphological, structural, and optical properties of the synthesized GO, Ag-GO and Au-GO samples, energy-dispersive X-ray spectroscopy (EDAX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy and UV–Vis spectroscopy are carried out. The accumulation of Ag and Au NPs on the surface of graphene oxide is observed by scanning electron microscopy. Measurements of the current–voltage (I-V) and transient photocurrent (I-t) at illumination intensities of 5 mW/cm2 by varying bias voltage in the range of 10–30 V with different wavelengths are examined. A bias voltage of 30 V and a monochromatic light of wavelength (480 nm) having intensity of 5 mW/cm2 at room temperature provided detectivities for Ag-GO and Au-GO nanocomposites of 4.96 × 108 (Jones) and 0.75 × 108 (Jones), respectively. According to the analysed photoresponse properties, Ag-GO and Au-GO nanocomposites have shown the potential for use in future optoelectronic device applications.

Recovery of cobalt from spent lithium ion batteries utilizing surface modified graphene oxide

Metal content present in the spent lithium ion batteries (LIBs) make their recycling vital for resources conservation and environmental sustainability. Cobalt, grouped among critical, valuable and strategic metals, is the basic part of the LIBs cathode and defines its recycling economic capacity. In the present work, an attempt has been made to develop an efficient hydrometallurgical technique based on solid phase extraction method for the recovery of cobalt from leach solution of waste LIBs. An adsorbent was synthesized by diazotization of p-phenylenediamine modified graphene oxide (GO-PPDA) sheets with disodium 1-nitroso-2-naphthol-3-6-disulphonate (nitroso R-salt, NRS) in one pot process of Mill's reaction. Maximum retention of cobalt (99.9%) was achieved at pH 5.5–6.5. Adsorption kinetics favour complexation as a separation mechanism following second order kinetics model with R2 value of 0.9999 with sample flow rate of 1.5 mL/min. Langmuir isothermal model (R2 = 0.998) also confirm monolayer chemisorption mechanism with 29.7 mg/g adsorption capacity. The two-step elution mechanism enables us to achieve 99.5% extraction efficiency with ~98% purity. The chelating adsorbent was found reasonably stable even after the 30th cycle of adsorption and desorption with <2% decrease in removal efficiency. The results show that the proposed adsorbent is successful in terms of selectivity, reusability, analytical merit and stability.

Effects of Surface Modified Graphene Oxide on the Cure Kinetics of Warm-Mixed Epoxy-Asphalt

Effects of Surface Modified Graphene Oxide on the Cure Kinetics of Warm-Mixed Epoxy-Asphalt

Effectively exerting the reinforcement of polyvinyl alcohol nanocomposite hydrogel via poly(dopamine) functionalized graphene oxide

Nature-inspired coating with polydopamine (PDA) is a promising way to improve the performance of graphene oxide (GO) based nanocomposites due to its high ability to enhance interactions in matrix-disperse systems. Here, we examined the capability of two types of PDA to develop the reinforced polyvinyl alcohol (PVA)/GO hydrogels. In the first mode, dopamine hydrochloride was polymerized as nanoparticles and then incorporated into PVA solution with GO nanoplatelets (P-NG hydrogel). In the second mode, polydopamine was polymerized in the presence of GO nanoparticles to obtain PDA surface-modified GO and then PVA nanocomposite hydrogel (P-CG sample). Rheological and tensile findings revealed that both types of PDA could act as a coupling agent and dramatically ameliorate viscoelastic and mechanical properties through establishment of hydrogen bonds and π-π interactions with the composite components. Also, PDA made the PVA-GO interfacial adhesion robust, leading to excellent self-healing properties. The outputs indicated that PDA in direct coated state could present better efficiency compared to the PDA nanoparticles. Moreover, porous network structure size in P-CG was smaller compared to that in P-NG, due to the increased crosslink density and higher net points interaction between the GO platelets and PVA chains, which leads to strong interfacial adhesion.

On the lubricity mechanism of carbon-based nanofluid fuels

Utilizing fuels blended with nanofluid particles may enhance fuel delivery and combustion in engines. However, the underlying tribochemistry related to fuel delivery when using nanofluids remains unclear. In this study, we investigate fuel lubricity over low-sulfur diesel (D100), diesel fuel containing 10 wt% ethanol (DE10), and DE10 blended with 50 to 200 ppm surface modified graphene oxide (mGO), i.e., G50, G100, and G200. The fuel lubricity experiment shows that as compared to D100, the DE10 fuel produced 50% larger wear volumes on rubbed balls, while lubrication with the G200 fuel reduced wear by 6%. The tribochemical reaction kinetic model developed in this work unravels the lubrication mechanism. The blended mGO reduces direct metal-to-metal contacts, produces graphitic tribofilms on wear tracks, and serves as tribo-active sources to grow frictional products.

Surface Modification of Graphene Oxide with Crosslinked Polymethacrylamide via RAFT Polymerization Strategy: Effective Removal of Heavy Metals from Aqueous Solutions

One of the efficient methods for enhancement of the heavy metal adsorption of nano graphene oxide (GO) is the surface modification through functional polymer. In this study, cross-linked polymethacrylamide (CPMAM) as hydrogel network was synthesized via reversible addition-fragmentation chain transfer (RAFT) technique to graft on the surface of GO activated phenylalanine (GO-Ph). The proposed mechanism for the grafting and chemically crosslinking reactions was proved with various techniques. The modified GO was employed as an excellent adsorbent for the removing of Cd(II) ions from aqueous solutions. The results indicated that ion adsorption basically relies on adsorbing time, solution pH, temperature, and initial Cd(II) concentration. In the optimized condition adsorption capacity was calculated to be 41.14 mg/g. Moreover, the adsorption kinetics and isotherm analysis demonstrated that the adsorption model was fitted with the pseudo-second-order and Freundlich isotherm models, respectively. The thermodynamic study showed that the ion adsorption process was endothermic and spontaneous. Based on the obtained results, the surface-modified GO with CPMAM has the potential to be used in sensitive environment that needs to completely remove Cd(II) ions.

Viscoelastic and fatigue properties of graphene and carbon black hybrid structure filled natural rubber composites under alternating loading

In this paper, the viscoelastic mechanics and fatigue properties of graphene and carbon black (CB) hybrid structure filled natural rubber (NR) composites under dynamic alternating loads studied. Dynamic viscoelastic analysis of different types of graphene rubber composites shows that doping graphene can significantly reduce composites' loss in a single cycle of dynamic loading. At the same time, the Payen effect of the composites can effectively suppress. The storage modulus and loss factor of natural rubber filled with graphene oxide (GO), reduced graphene oxide (RGO), surface modified graphene oxide (MGO), and carbon black are still higher than those filled with carbon black. This phenomenon indicates that graphene, especially graphene with surface functional groups, can change the conformation and free volume of rubber. The test results of composites under low-frequency dynamic loading are similar to those at high temperatures. Dynamic fatigue analysis shows that GO/CB/NR, RGO/CB/NR, and MGO/CB/NR have better fatigue resistance than CB/NR. These results show that graphene, especially the interface modified graphene carbon black hybrid structure, has better viscoelasticity than carbon black filled natural rubber composites. Our work provides a new choice for designing and applying rubber composite materials in buildings, piers, and track bearings.

Organic Functionalized Graphene Oxide Behavior in Water.

Surface modified graphene oxide (GO) has received broad interest as a potential platform material for sensors, membranes, and sorbents, among other environmental applications. However, compared to parent (unmodified) GO, there is a dearth of information regarding the behavior of subsequently (secondary) modified GO, other than bulk natural organic matter (NOM) coating(s). Here, we systematically explore the critical role of organic functionalization with respect to GO stability in water. Specifically, we synthesized a matrix of GO-based materials considering a carefully chosen range of bound organic molecules (hydrophobic coatings: propylamine, tert-octylamine, and 1-adamantylamine; hydrophilic coatings: 3-amino-1-propanol and 3-amino-1-adamantanol), so that chemical structures and functional groups could be directly compared. GO (without organic functionalization) with varying oxidation extent(s) was also included for comparison. The material matrix was evaluated for aqueous stability by comparing critical coagulation concentration (CCC) as a function of varied ionic strength and type (NaCl, CaCl2, MgCl2, and MgSO4) at pH 7.0. Without surface derivatization (i.e., pristine GO), increased stability was observed with an increase in the GO oxidation state, which is supported by plate–plate Derjaguin, Landau, Verwey and Overbeek (DLVO) energy interaction analyses. For derivatized GO, we observed that hydrophilic additions (phi-GO) are relatively more stable than hydrophobic organic coated GO (pho-GO). We further explored this by altering a single OH group in the adamantane-x structure (3-amino-1-adamantanol vs. 1-adamantylamine). As expected, Ca2+ and monovalent co-ions play an important role in the aggregation of highly oxidized GO (HGO) and phi-GO, while the effects of divalent cations and co-ions were less significant for pho-GO. Taken together, this work provides new insight into the intricate dynamics of GO-based material stability in water as it relates to surface functionalization (surface energies) and ionic conditions including type of co- and counter-ion, valence, and concentration.

Experimental test and curve fitting of creep recovery characteristics of modified graphene oxide natural rubber and its relationship with temperature

The creep recovery properties of different graphene-doped rubber and the effect of temperature on them were studied. Doping graphene, especially with the surface functional group or surface microstructure, can significantly improve the creep resistance of natural rubber (NR). The permanent creep of each composite tested under the same conditions for 20 min. Graphene oxide, hydrazine hydrate reduced graphene oxide, and 3-aminopropyltriethoxysilane (APTS) grafted graphene oxide was 33%, 16%, and 51% lower than those filled with carbon black respectively. Four parameter model and Weibull distribution function used to analyze and evaluate the creep and recovery test results of composite rubber. These curve fitting results can adequately describe the influence of different types of nanofillers on the creep and recovery properties of composite rubber. The long-term creep of composites forecasted by the time-temperature superposition principle (TTSP). The results show that graphene doping can improve the creep resistance of the rubber. Besides, graphene oxide and surface-modified graphene oxide had better creep resistance than reduced graphene oxide filled natural rubber. It can see that the interfacial properties between the graphene sheet and the natural rubber matrix play an essential role in the creep and recovery properties of graphene/natural rubber composites.

PVC/rice straw/SDBS-modified graphene oxide sustainable Nanocomposites: Melt mixing process and electrical insulation characteristics

The incorporation of nanomaterials in the mixing process of polymers can effectively improve the melt mixing rheology of composites. This fact can be employed to control the morphology of sustainable composites comprised of incompatible ingredients such as natural fibers and polymers. The conventional solution to the incompatibility of natural-fiber fillers and polymers is to surface modify the natural filler. In this work, the role of graphene oxide and surface-modified graphene oxide nanosheets on the mixing rheology of a PVC/rice straw system are studied and impacts these nanosheets have on the viscosity of this sustainable system are used to reduce the morphological imperfections. The introduction of either graphene oxide or sodium dodecylbenzenesulfonate (SDBS)-modified graphene oxide nanosheets increased the melt mixing viscosity of PVC/rice straw compounds. Such a change in the melt mixing rheology of compounds resulted in an improvement in the morphological and structural characteristics. When only 1 phr SDBS-modified graphene oxide nanosheets were introduced in a PVC system filled with 15 phr rice straw fibers, more than 23 and 41% enhancement in the tensile ultimate strength of the system is achieved, compared to the neat PVC and the PVC/15 phr rice straw composite, respectively. Moreover, dynamic-mechanical results confirm that the incorporation of 1 phr SDBS-modified graphene oxide nanosheets resulted in more than 7% reduction in the damping peak intensity of the system, suggesting the formation of interactions between system ingredients. The electrical conductivity of the fabricated sustainable PVC/rice straw/SDBS-modified graphene oxide nanocomposite is in the range of 10−9–10−5 S/m, suggesting it can be a good candidate for insulating applications.

Influence of surface modified graphene oxide on the mechanical performance and curing kinetics of epoxy resin

AbstractIn this study, the hyperbranched polyester were successfully grafted onto graphene oxide (GO). The mechanical performance and curing kinetics of epoxy resin (EP), EP/ graphene oxide (EP/GO), and EP/ hyperbranched polyester grafted GO (EP/GO‐B) were investigated by means of mechanical tests and differential scanning calorimetry (DSC). Results revealed that the presence of GO lowered the cure temperature and accelerated the curing of EP, and the addition of GO‐B exhibited a stronger effect in accelerating the cure of EP compared with GO. Activation energies were calculated using Kissinger approach, and Ozawa approach, respectively. Results revealed lowered activation energy after the addition of GO or GO‐B at low degrees of cure, indicating that GO had a large effect on the curing reaction. The presence of GO facilitated the curing reaction, especially the initial epoxy‐amine reaction. Moreover, GO‐B exhibited better performance. Related mechanism was proposed.

Triple-synergistic 2D material-based dual-delivery antibiotic platform

Two-dimensional (2D) nanomaterials have raised significant interest in not only energy and environmental fields but also biomedical areas. Among these materials, one type that has many interesting properties and possesses numerous exciting applications is graphene oxide (GO)-based 2D materials. However, their poor stability in aqueous solutions and weak bioactivities limit their use in biomedical applications, especially antimicrobial fields. In this study, GO was functionalized with hydrophilic polymers and used as a vector for silver nanoparticles (Ag NPs) and sulfadiazine (SD). The stability of the material in aqueous solutions was greatly improved. The antibacterial activity of the novel hybrid antibacterial system (HAS) was enhanced by over 3 times compared to that of the system lacking SD. The antibacterial performance of the HAS was due to the triple synergy: bacterial capping, puncture, and inhibition. This study provides new insights into the design and fabrication of surface-modified GO and carbon materials and their 2D hybrid multifunctional materials for advanced applications including biomedical and especially antibacterial applications, broadening the design and application scope of carbon and 2D materials.

Bio-elastomer nanocomposites reinforced with surface-modified graphene oxide prepared via in situ coordination polymerization

This article proposes a method to produce bio-elastomer nanocomposites, based on polyfarnesene or polymyrcene, reinforced with surface-modified graphene oxide (GO). The surface modification is performed by grafting alkylamines (octyl-, dodecyl-, and hexadecylamine) onto the surface of GO. The successful grafting was confirmed via spectroscopic (FTIR and Raman) and X-ray diffraction techniques. The estimated grafted amines appear to be around 30 wt%, as calculated via thermogravimetric analysis, increasing the inter-planar spacing among the nanosheets as a function of alkyl length in the amine. The resulting modified GOs were then used to prepare bio-elastomer nanocomposites via in situ coordination polymerization (using a ternary neodymium-based catalytic system), acting as reinforcing additives of polymyrcene and polyfarnesene. We demonstrated that the presence of the modified GO does not affect significantly the catalytic activity, nor the microstructure-control of the catalyst, which led to high cis-1,4 content bio-elastomers (>95%). Moreover, we show via rheometry that the presence of the modified-GO expands the capacity of the elastomer to store deformation or applied stress, as well as exhibit an activation energy an order of magnitude higher.

Preparation and aggregate state regulation of co-assembly graphene oxide-porphyrin composite Langmuir films via surface-modified graphene oxide sheets

Constructing graphene oxide (GO)-based 2D nanomaterials via facile and appropriate methods have aroused much attention due to their potential applications in many fields. Herein, by Langmuir-Blodgett (LB) technique, we have successfully fabricated GO-based films composited with porphyrin molecules. By the reaction of diazotization and Fischer osazone, different surface states of GO sheets with sulfonate groups were obtained. The amphiphilic GO and surface modified GO sheets could spontaneously form composite films at the air/water interface with porphyrin molecules (TMPyP) by electrostatic interactions and π-π stacking. Since the sheets can perfectly float on the interface, the TMPyP molecules were adsorbed on the floating-layers and self-assembled into highly ordered J-aggregate structures. The morphological characterization results showed the composite films with smooth and dense surface. Due to the different surface state of the nanosheets, the aggregate states of porphyrin molecules were different which could be demonstrated in the UV–vis spectra. The results indicated that the induction of sulfonate groups and the types of oxygen-containing groups have played important roles for regulating the aggregate state of porphyrin molecules.

Sandwich membranes based on PVDF-g-4VP and surface modified graphene oxide for Cu(II) adsorption.

UV photo-preactivation/thermally-induced grafting was employed for grafting 4-vinylpyridine (4-VP) on polyvinylidene fluoride (PVDF), and graphene oxide (GO) was modified with 4'-carboxy-2,2':6',2"-terpyridine (CTPy). Then sandwich PVDF-g-4VP/GO-CTPy/polytetrafluoroethylene (PTFE) membrane was fabricated for adsorption of Cu (II) as a model. The membrane formation, static adsorption thermodynamics, kinetics and dynamic adsorption/desorption were studied. The results showed that, the addition of polyethylene glycol (PEG 4000) as porogen can significantly increase the porosity and adsorption capacity of the membranes. The adsorption could be well described by the Langmuir model and pseudo-second-order kinetic model. The breakthrough volume and saturated volume increased with rising GO-CTPy contents. The adsorption capacity of sandwich membranes was much higher than that of mixed matrix membranes. The sandwich membrane also exhibited excellent reusability in dynamic adsorption/desorption cycles, demonstrating great potential in adsorption of trace Cu (II).

Characterization of Reduced and Surface-Modified Graphene Oxide in Poly(Ethylene-co-Butyl Acrylate) Composites for Electrical Applications.

Promising electrical field grading materials (FGMs) for high-voltage direct-current (HVDC) applications have been designed by dispersing reduced graphene oxide (rGO) grafted with relatively short chains of poly (n-butyl methacrylate) (PBMA) in a poly(ethylene-co-butyl acrylate) (EBA) matrix. All rGO-PBMA composites with a filler fraction above 3 vol.% exhibited a distinct non-linear resistivity with increasing electric field; and it was confirmed that the resistivity could be tailored by changing the PBMA graft length or the rGO filler fraction. A combined image analysis- and Monte-Carlo simulation strategy revealed that the addition of PBMA grafts improved the enthalpic solubility of rGO in EBA; resulting in improved particle dispersion and more controlled flake-to-flake distances. The addition of rGO and rGO-PBMAs increased the modulus of the materials up to 200% and the strain did not vary significantly as compared to that of the reference matrix for the rGO-PBMA-2 vol.% composites; indicating that the interphase between the rGO and EBA was subsequently improved. The new composites have comparable electrical properties as today’s commercial FGMs; but are lighter and less brittle due to a lower filler fraction of semi-conductive particles (3 vol.% instead of 30–40 vol.%).