Adsorption Of Graphene Oxide Research Articles

Preparation and characterization of polyethyleneimine functionalized magnetic graphene oxide as high uptake and fast removal for Hg (II).

Polyethyleneimine functionalized magnetic graphene oxide adsorbent (PEI-mGO) was synthesized by introducing polyethyleneimine onto Fe3O4/graphene oxide. The structures and morphologies of PEI-mGO was identified by using Fourier-tranform infrared (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) methods. Quantities of bar-like Fe3O4 nanoparticles were observed on the surfaces of PEI-mGO. The adsorption of PEI-mGO for Cu(II), Pb(II), Hg(II), Co(II) and Cd(II) was compared. The adsorption results indicated that PEI-mGO showed higher uptake for Hg(II) than the other ions. The influence of various variables for the adsorption of Hg(II) on PEI-mGO was explored. The adsorption kinetics and isotherm could be described well by the pseudo-second-order and Langmuir models. The maximal uptake of PEI-mGO for Hg(II) from Langmuir model was 857.3 mg g-1, which was higher than that reported previously. The adsorption removal was a fast and endothermic process governed by the chemical process. The uptake increased with increasing temperature. PEI-mGO showed an excellent performance for removal of Hg(II) with 93.3% removal efficiency from simulated wastewater. Adsorption-desorption cycled experiments indicated that PEI-mGO could be recycled. PEI-mGO could be easily separated from the adsorbed solution by using a magnet. Hence, this novel adsorbent would be promising for the removal of Hg(II) from wastewater.

Strength Characteristics of Cement-Modified Iron Tailings and Their Adsorption on Graphene Oxide

To explore the mechanical properties of cement-modified iron tailings (CIT) and its adsorption on graphene oxide (GO), the unconfined compressive strength (UCS) tests of CIT with 10% cement were carried out for 7 and 28 days. CIT adsorption of GO was carried out under the conditions of different pH, CIT dosage, and GO initial concentration. The micro characterization of CIT adsorption of GO was carried out by SEM, TEM, AFM, EDS, FT-IR, XRD, and XPS. The results show that: (1) the CIT strength of 28 d curing age is 1202 kPa is twice of 7 d. (2) At the same pH, the GO adsorption effect of CIT at 7 days curing age was better than that at 28 days. When pH is 6, CIT content is 50 mg, and GO initial concentration is 100 mg.L-1, CIT has the best adsorption effect on the GO, and the removal rate reached 93.5%. (3) Through microscopic characterization, it can be concluded that the bound water in the CIT structure and the asymmetric stretching vibration of the O-H bond in hydrated calcium silicate (C-S-H) are the main factors affecting the adsorption of GO. The above research results show that CIT not only has good strength properties but also has good adsorption properties for GO. CIT is a potential environmental treatment material.

Study on Adsorption Properties and Mechanism of Graphene Oxide (GO) by Kaolin

Kaolin was used as an adsorbent to remove toxic graphene oxide (GO) from an aqueous solution. The adsorption properties and mechanism of GO by Kaolin were systematically studied by various characterization techniques and methods. The effects of pH, amount of absorbent, and initial concentration of GO on the adsorption of GO by Kaolin were studied in detail. The results show that the interaction between GO and Kaolin is realized by the O-C=O bond, and the adsorption of GO by Kaolin is a chemical adsorption process. Under the optimized conditions (pH=3, T=303 K, equilibrium time = 6 h, C0 = 60 mg·L-1), the removal rate of GO reached 97.1% (Kaolin=70 mg), and the adsorption capacity reached 45.3 mg·g-1 (Kaolin=50 mg). According to the experimental results, Kaolin may be a promising material, which can effectively eliminate GO from an aqueous solution. The results of this study provide key information about the migration and potential fate of GO in the natural environment.

Graphene coated sand for smart cement composites

• The GO on the GO-coated sand anneals and then microwaves to graphene-coated sand. • Self-sensing cement composites enable by nano-engineers cement-aggregate interfaces. • The conductive path in mortar mainly consists of G@sand with ITZ located in between. • M-G@FAg mortar demonstrates electrical resistivity of 960 Ω·cm and an FCR of ∼ 18%. Unlike conventional approaches of direct addition of carbon-based conductive fillers into cement matrix in developing smart sensing composites, this study proposes a targeted and therefore more efficient approach through nano-surface engineering of the sand. Specifically, a simple method that enables uniform adsorption of graphene oxide onto the surface of the sand particles, followed by simple annealing and microwave treatment to prepare graphene-coated sand (conductive aggregates). Scanning electron microscopy indicates that about 62.2% of the sand surface area is successfully coated by graphene, with an average thickness of approximately 8.8 nm. The mortar incorporating conductive aggregates demonstrates outstanding electrical conductivity (resistivity of 960 Ω·cm) and a high fractional change in resistivity of ∼ 18% under cyclic compressive loading, which outperforms previously reported results obtained by direct addition of graphene or carbon nanotubes at equivalent concentrations. The use of conductive aggregates in mortars also results in other minor benefits such as a slight enhancement in flowability and reduction in water sorptivity. All of these were achieved without substantial reduction in 28-d compressive strength. These findings demonstrate a great potential of aggregate surface nano-engineering for developing smart cement-based composites for practical sensing applications.

Highly conductive and sensitive piezoresistive cement mortar with graphene coated aggregates and carbon fiber

Traditionally, conductive fillers are mixed directly with cement matrix before binding with aggregates to develop piezoresistive cement-based sensors. This results in the most vulnerable region, interfacial transition zone (ITZ), from which microcracks are initiated, merely located at the periphery of the conductive network and thus limits the sensitivity of the smart sensor. This study proposes a strategy to construct a three-dimensional (3D) conductive network in the mortar with ITZ directly embedded in it, thus greatly increasing both the conductivity and piezoresistivity without significantly sacrificing mechanical property. Highly conductive graphene-coated fine aggregates (termed conductive G@FAg particles) are prepared by adsorption of graphene oxide (GO) onto the fine aggregates (FAg) surface, followed by simple annealing and microwave treatment. The combined usage of conductive G@FAg particles and 0.1 wt% 6 mm-CF results in an outstanding electrical conductivity (resistivity of 580 Ω cm) and an excellent fractional change in resistivity (FCR of 30%) under cyclic compressive loading, with a negligible compressive strength loss of 3.1%. Remarkably, the addition of conductive G@FAg particles together with 0.5 wt% 10 mm-CF leads to an excellent conductivity (resistivity of 165 Ω cm) and self-sensing ability (FCR of ∼90%), which outperforms the previously reported mortar directly incorporated with the same concentration of CF and graphene. The much-improved conductivity and FCR value with such a low weight percentage of conductive carbon materials are attributed to the unique 3D network of conductive channels.

Incorporating hard-soft acid-base theory in multi-aspect analysis of the adsorption mechanism of aqueous heavy metals by graphene oxide

Water contamination by heavy metals is a serious environmental concern. To unravel the “species resolved” interaction mechanism of heavy metals with graphene oxide (GO), a multi-aspects analyses incorporating metal species distribution, GO surface charge, adsorption behavior and fitting, hard-soft acid-base (HSAB) theory, Fourier transformation infrared spectroscopy and X-ray photoelectron spectroscopy were performed. For pH 7 and T = 25 °C, adsorptions of aqueous Cd(Ⅱ) and Pb(Ⅱ) with equal initial concentrations of 300 mg L−1 by GO at 500 mg L−1 equilibrated in 15 min. The corresponding adsorption percentage and quantity for Cd(Ⅱ) were 98.04% and 588.22 mg g−1 and those for Pb(Ⅱ) were 92.10% and 552.56 mg g−1. When pH ≤ 7, bare Cd2+ and Pb2+ were the dominant metal species adsorbed by GO via ion exchange and chemical complexation. When pH ≥ 7, hydroxyl-complexed species were the dominant ones adsorbed by GO via precipitation, ion exchange, and chemical complexation. Electron transfer and energy lowering induced by the GO–heavy metal interaction, calculated based on HSAB theory, illuminated two points: (1) OH had a stronger binding affinity than COOH toward either Cd(Ⅱ) or Pb(Ⅱ) and (2) either OH or COOH had a stronger binding affinity toward Cd(Ⅱ) than Pb(Ⅱ). Explorations of this work may provide guidance in developing efficient graphene-based adsorbents for wastewater remediation.

The influences of internal interactions and functional groups on the adsorption of graphene and graphene oxide with alumina substrate

Molecular dynamics is used to simulate the adsorption process of graphene and graphene oxide fragments with different sizes on the (0001) crystal plane of Al2O3. The results reveal that the influence of internal interaction and functional groups on graphene and graphene oxide adsorbed by the alumina surface. From the atomic simulation, it can be found that the Coulomb interaction between graphene and the substrate can enhance the interaction between graphene oxide and the substrate after oxidation. It also promotes the spontaneous adsorption of graphene oxide to the substrate, and its influence on the process is much greater than that of the van der Waals force interaction. Before graphene was oxidized, the Coulomb interaction and van der Waals force interaction inhibited the desorption of graphene, but the Coulomb interaction was relatively weak. In addition, the increase of the size of graphene and graphene oxide can reduce the adhesion energy and desorption free energy, resulting in the instability of adsorption state, which is more unfavorable to the occurrence of the adsorption process. In graphene oxide, the oxidized carbon atom bears most of the potential energy and induces the instability of the structure. Its three functional groups, carboxyl, hydroxyl and epoxy, play a role in reducing the overall potential energy of graphene oxide and stabilizing the structure of graphene. Therefore, compared with pristine graphene, graphene oxide with a high degree of oxidation can form a much stable coating on the alumina substrate. By means of multiscale modelling and simulation, this article may theoretically contribute to the application of graphene coating on the aluminum alloy surface and gives guiding opinions for enhancing the strength of graphene coating.

Effective removal of phenol from wastewater using a hybrid process of graphene oxide adsorption and UV-irradiation

The focus of this work is the removal of phenol from water by graphene oxide (GO) nanoparticles, prepared by two different methods, through a hybrid adsorption–UV-irradiation process. The GO1 and GO2 were prepared using (H2SO4 and H3PO4) and (H2SO4, H3PO4, and HNO3), respectively. The effect of different parameters namely, pH, initial phenol concentration, and temperature on the adsorption process was investigated. Fourier transform infrared spectroscopy and scanning electron microscopy were used to characterize the prepared graphene oxides (GO1 and GO2). Various adsorption isotherm models were investigated including Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich adsorption isotherm models. The results showed that UV-irradiation had a positive effect on the adsorption process as the adsorption capacity increased. Additionally, maximum removal percentage was obtained at pH 2 for GO1 for both experimental sets. Similarly, GO2 without exposure to UV-irradiation showed the highest adsorption capacity at pH 2, while with the effect of UV-irradiation, the optimum pH was 6. Furthermore, increasing the initial concentration of phenol led to the increase in adsorption until it reached an equilibrium where the adsorption decreased and remained constant. Furthermore, the maximum adsorption capacity increased with the effect of UV exposure from 70.43% to 90.82% for GO1 and from 86.75% to 95.95% for GO2. Moreover, increasing the temperature caused the adsorption capacity to decrease and the thermodynamic results showed that the adsorption processes were feasible and spontaneous for GO1 (with and without UV exposure), and GO2 (only with UV exposure).

Adsorption of Dyes Using Graphene Oxide-Based Nano-Adsorbent: A Review

Graphene Oxide (GO) based adsorbents have attracted much attention from researchers because there have been many reports that they are effective for removing dyes from aqueous environments. That is because GO has good mechanical, electrical, optical and chemical properties, so graphene and its derivatives, such as graphene oxide, have been used in various applications in the field of environmental management. Modifying GO into nano size is an effort to improve its performance in removing dyes. This review uses a database from Science Direct, Google Scholar and Springer, which was screened using graphene oxide, pigments, adsorption and nano adsorbent. The performance of the nano adsorbent showed quite good results in the removal of dyes. The isotherm model suitable for adsorption varies between Langmuir, Freundlich and Redlich-Peterson isotherms. Pseudo-second-order (PSO) is the best model to explain the adsorption process kinetics. Nano-adsorbent modification can be reused at least five times with a reduced adsorption capacity of 4-8%. Studies related to adsorption with GO-based nano adsorbents show promising results in pollutant removal. Still, aspects such as synthesis method, surface functional groups interaction and dye ions and the stability of synthesis products need to be investigated further.

Removal of direct blue 71 and methylene blue from water by graphene oxide: effects of charge interaction and experimental parameters

Graphene oxide (GO) was synthesized by modified the Hummers method and used as an effective adsorbent for removing direct blue 71 (DB 71) and methylene blue (MB) from water. Surface characteristics of the produced GO materials and related physiochemical properties of the organic dyes were systematically examined to reveal removal mechanisms. Thermodynamics, kinetics, and regeneration of GO adsorbent were also studied to disclose the nature of the adsorption and the reusability of adsorbent. GO adsorbed the cationic MB better than the anionic DB 71 mainly due to the electrostatic attraction between negatively charged GO’s surface and the positively charged MB molecules. Langmuir isotherm better described MB and DB 71 adsorption than the Freundlich model. The adsorption capacities of GO of 476.19 mg/g (for MB) and 175.41 mg/g (for DB 71) were considerably higher than those of other adsorbents such as activated carbon, chitosan, and biochar. MB and DB 71 adsorption process was spontaneous, endothermic, and governed by both physisorption and chemisorption. GO could be regenerated by methanol and dilute HCl solutions, and reused as an efficient adsorbent. This study provides a comprehensive data on the MB and DB71 adsorption processes, and an efficient approach on the regeneration of GO adsorbent.

Integrated ultrasound-assisted magnetic solid-phase extraction for efficient determination and pre-concentration of polycyclic aromatic hydrocarbons from high-consumption soft drinks and non-alcoholic beers in Iran.

In the present research, an ultrasound-assisted magnetic solid-phase extraction coupled with a gas chromatography-mass spectrometry hybrid system was developed for the extraction/determination of trace amounts of polycyclic aromatic hydrocarbons in high-consumption soft drinks and non-alcoholic beers in Iran using magnetite graphene oxide adsorbent. The magnetite graphene oxide was characterized by scanning electron microscope, transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and vibrating-sample magnetometer techniques. The highest extraction recovery (73.05%-95.56%) and enrichment factor (90.65-106.38) were obtained at adsorbent mass: 10mg, adsorption time: 30min, salt addition: sodium chloride 10% w/v, desorption time: 20min, eluent type: hexane: acetone (1:1, v/v), and desorption solvent volumes: 200 μl. Under optimum conditions, the linearity range for polycyclic aromatic hydrocarbons determination was 0.2-200ng/mlwith a coefficient of determination>0.993, the limit of detection=0.09-0.21ng/ml, the limit of quantitation=0.3-0.7ng/ml, and relative standard deviation<8.1%, respectively. Relative recoveries in spiked real samples ranged from 94.67 to 109.45% with a standard deviation<6.05%. The proposed method is effective, sensitive, and reusable and it is promising for the analysis of polycyclic aromatic hydrocarbons residues in environmental samples.

Physical Adsorption of Graphene Oxide onto Polymer Latexes and Characterization of the Resulting Nanocomposite Particles.

Polymer/graphene oxide (GO) nanocomposite particles were prepared via heteroflocculation between 140–220 nm cationic latex nanoparticles and anionic GO nanosheets in either acidic or basic conditions. It is demonstrated that nanocomposite particles can be formed using either poly(2-vinylpyridine)-b-poly(benzyl methacrylate) (P2VP–PBzMA) block copolymer nanoparticles prepared by reversible-addition chain-transfer (RAFT)-mediated polymerization-induced self-assembly (PISA), or poly(ethylene glycol)methacrylate (PEGMA)-stabilized P2VP latexes prepared by traditional emulsion polymerization. These two latexes are different morphologically as the P2VP–PBzMA block copolymer latexes have P2VP steric stabilizer chains in their corona, whereas the PEGMA-stabilized P2VP particles have a P2VP core and a nonionic steric stabilizer. Nevertheless, both the P2VP–PBzMA and PEGMA-stabilized P2VP latexes are cationic at low pH. Thus, the addition of GO to these latexes causes flocculation to occur immediately due to the opposite charges between the anionic GO nanosheets and cationic latexes. Control heteroflocculation experiments were conducted using anionic sterically stabilized poly(potassium 3-sulfopropyl methacrylate)-b-poly(benzyl methacrylate) (PKSPMA–PBzMA) and nonionic poly(benzyl methacrylate) (PBzMA) nanoparticles to demonstrate that polymer/GO nanocomposite particles were not formed. The degree of flocculation and the strength of electrostatic interaction between the cationic polymer latexes and GO were assessed using disc centrifuge photosedimentometry (DCP), transmission electron microscopy (TEM), and UV–visible spectrophotometry. These studies suggest that the optimal conditions for the formation of polymer/GO nanocomposite particles were GO contents between 10% and 20% w/w relative to latex, with the latexes containing P2VP in their corona having a stronger electrostatic attraction to the GO sheets.

A design of red emission CDs-based aptasensor for sensitive detection of insulin via fluorescence resonance energy transfer

We successfully designed an aptasensor based on the red emission carbon dots (R-CDs) and effectively detected insulin (INS) via fluorescence resonance energy transfer (FRET). In the process, the aptamer (apt) labeled with R-CDs (R-CDs@apt) was used as fluorescence donor and graphene oxide (GO) was used as fluorescence receptor. The successful detection due to the aptamer sequence has a certain affinity for Go and INS, while the affinity for INS is stronger than that of GO. When INS is not added to the detection system, the aptamer is adsorbed onto the surface of GO, shortening the distance between R-CDs@apt and GO, resulting in FRET and the quenching of fluorescence of R-CDs@apt. When INS was added to the detection system, the aptamer selectively bound INS and separated from the adsorption of GO, FRET gradually disappeared and the fluorescence of R-CDs@apt/GO/INS system was restored. By comparing the changes of fluorescence intensity before and after adding INS, the detection of INS was implemented. The aptasensor has a good linear curve with the detection limit of as low as 1.1 nM when the concentration of INS reached 1.3–150 nM. This method has excellent selectivity and anti-interference. Therefore, it is a potential method for detecting substances in biological fluids.

Synthesis and characterization of exfoliated beta-cyclodextrin functionalized graphene oxide for adsorptive removal of atenolol

In this present work, a low-cost adsorbent is reported using exfoliated graphene oxide (GO) functionalized with cyclic polysaccharide via an easily scalable, sustainable, and eco-friendly method for the removal of atenolol, a beta-blocker from an aqueous solution. The beta-cyclodextrin (BCD) functionalized GO (BCDGO) adsorbent was characterized using Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), X-ray photoelectron spectroscopy (XPS), Fourier Transform Infrared Spectrometer (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), Thermogravimetric analyzer (TGA), Dynamic Light Scattering (DLS) analysis, Zeta potential analysis, and BET analyzer. IFFT analysis using a TEM image was done, which indicated an increase in d-spacing from 0.22 nm in GO to 0.74 nm in BCDGO. It was observed that BCDGO is an efficient adsorbent in removing atenolol and showed faster kinetics compared to GO as determined from a UV–Visible spectrophotometer. FTIR and Raman spectroscopy confirmed functionalization by BCD molecules. XRD analysis indicated an increase in crystallite size, and BET analysis showed that BCDGO had increased surface area by 25 times compared to conventional GO synthesized by modified Hummer's method. The mechanistic insight corresponding to the electrostatic interaction of atenolol at the interface of the BCDGO is established using zeta potential analysis. The recyclability of BCDGO was established as it could remove 60% atenolol after four consecutive cycles with an atenolol concentration of 50 μM.

Graphene Functionalized Cotton Nonwoven for Thermotherapy

ABSTRACT Graphene-based electroconductive textile materials are advantageous over metal/gel-based heating pads for thermotherapy because of their flexibility, processability, and ability to maintain a constant temperature for an extended period. The electro-thermal properties of graphene-based nonwoven depend on its surface resistivity which in turn depends on the amount of graphene oxide (GO) deposition. In this work, highly conductive, flexible, lightweight, and antibacterial graphene functionalized cotton nonwoven with excellent electro-thermal performance is reported. For this, needle punched nonwoven structure is designed and its construction variables (Fabric GSM, punch density, and depth of penetration) are optimized with the Box-Behnken response surface design to achieve maximum GO adsorption and minimum surface resistivity. The lowest surface resistivity of 727.57 Ω sq−1 is achieved at 22.18% GO add-on. The functionalized fabric shows excellent electro-thermal properties and a maximum surface temperature of 118°C is achieved at 30V DC supply. The change in surface resistivity of rGO-cotton (reduced graphene oxide coated cotton) is insignificant even after atmospheric aging for 10 weeks, 4 washings and 10 rubbings. Antibacterial activity of 97.10% is achieved toward Staphylococcus aureus bacterium.

A label-free cyclic amplification strategy for microRNA detection by coupling graphene oxide-controlled adsorption with superlong poly(thymine)-hosted fluorescent copper nanoparticles.

Herein, based on a terminal deoxynucleotidyl transferase (TdT)-mediated superlong poly-T-templated-copper nanoparticles (poly T-CuNPs) strategy, a simple, universal and label-free fluorescent biosensor for the detection of miRNA was constructed by employing graphene oxide (GO) and DNase I. In this strategy, GO and DNase I were used as a switch and amplifier of the signal generation pathway, respectively, and the fluorescence of poly T-CuNPs was used as the signal output. In the presence of target miRNA, the DNA dissociated from the GO surface by forming a miRNA/DNA duplex and was degraded by DNase I. The short oligos with 3'-OH, the product of DNase I degradation, could be recognized by the TdT and added to a long poly-T tail. Finally, the fluorescence signal was output through the synthesis of poly T-CuNPs. As a proof of concept, let-7a was analyzed. The method showed good sensitivity and selectivity with a linear response in the 50 pM-10,000 pM let-7a concentration range and a 30 pM limit of detection (LOD=30 pM, R2=0.9954, the relative standard deviation were 2.79%-5.30%). It was also successfully applied to the determination of miRNA in spiked human serum samples. It showed good linearity in the range of 500-10000 pM (R2=0.9969, the relative standard deviation were 1.61%-3.85%). Moreover, both the adsorption of GO and the degradation of DNase I are DNA sequence-independent; thus, this method can be applied to the detection of any miRNA simply by changing the assisted-DNA sequence.

Polymeric micro gas preconcentrators based on graphene oxide and carbon nanopowder adsorbents for gas detection application

In this study, an application of novel polymer-based microfluidic channels for preconcentration and detection of methane gas is investigated. Poly (methyl methacrylate) (PMMA) microfluidic channel is filled by graphene oxide (GO) as a new adsorbent for thermal preconcentration and carbon nanopowder is loaded into a polydimethylsiloxane (PDMS) microfluidic channel. The effective microfluidic channels area is 14 mm × 10 mm. The laser cutting and etching followed by thermally-solvent bonding process are used for PMMA microfluidic channel fabrication. Also, PDMS microfluidic channel is fabricated by SU-8 molding technique, lithography process, and oxygen plasma bonding on glass. SEM, Raman spectroscopy, and FTIR characterizations are carried out for investigation of the synthesized GO. The amount of electrical power consumption of devices is also investigated by simulation and experiment. The performance of both micro preconcentrators (μPCs) are compared through the similar experimental tests which exhibit the suitable performance of fabricated μPCs with proper repeatability for preconcentration purposes. The effect of gas flow rate, heating rate, gas exposure time, and gas concentration are investigated for both microfluidic channels and their optimized values were obtained. According to the lower desorption temperature of GO, despite its slightly lower response (10.41) compared to carbon nanopowder μPCs (12.34), due to its almost half power consumption (0.375 W in comparison with 0.8 W), it can be an appropriate candidate for preconcentration applications. PMMA and PDMS-based microfluidic channels show promising choices in the preconcentration application for the adsorbents with low desorption temperatures. As a result, PMMA as a low-cost material with a simple fabrication process in microchannels and GO as the novel adsorbent material can be suitable candidates in low working temperature and rapid preconcentration devices. • Microfluidic channels are fabricated based on poly (methyl methacrylate) (PMMA), and polydimethylsiloxane (PDMS) • Graphene oxide (GO) and carbon nanopowder are used as the adsorbent materials for PMMA and PDMS microfluidic channels, respectively. • The effect of gas flow rate, heating rate, gas exposure time, and gas concentration are investigated to achieve the optimized values. • The power consumption and temperature distribution of heater are studied through the simulation.

Liquid Superlubricity Enabled by the Synergy Effect of Graphene Oxide and Lithium Salts

In this study, graphene oxide (GO) nanoflakes and lithium salt (LiPF6) were utilized as lubrication additives in ether bond−containing dihydric alcohol aqueous solutions (DA(aq)) to improve lubrication performances. The apparent friction reduction and superlubricity were realized at the Si3N4/sapphire interface. The conditions and laws for superlubricity realization have been concluded. The underlying mechanism was the synergy effect of GO and LiPF6. It was proven that a GO adsorption layer was formed at the interface, which caused the shearing interface to transfer from solid asperities to GO interlayers (weak interlayer interactions), resulting in friction reduction and superlubricity realization. In addition to the GO adsorption layer, a boundary layer containing phosphates and fluorides was formed by tribochemical reactions of LiPF6 and was conducive to low friction. Additionally, a fluid layer contributed to friction reduction as well. This work proved that GO−family materials are promising for friction reduction, and provided new insights into realizing liquid superlubricity at macroscale by combining GO with other materials.

Fluorine-18 Fluorodeoxyglucose Isolation Using Graphene Oxide for Alternative Radiopharmaceutical Spillage Decontamination in PET Scan

Radiopharmaceuticals (RPC) used for diagnostic and therapeutic purposes in nuclear medicine may contaminate surface areas due to spillage during its preparation or accident during RPC transfer from laboratory to the treatment room. Fluorine-18 Fluorodeoxyglucose (18F-FDG) is the most common RPC for positron emission tomography (PET) scan in nuclear medicine due to its ideal annihilation converted energy at 511 keV and short half-life at 109.8 min. Ineffective medical waste management of 18F-FDG may pose a risk to the environment or cause unnecessary radiation doses to the personnel and public. Depending on the incident rate of these events, simple decontamination methods such as the use of chemicals and swabs might not be cost-effective and sustainable in the environment. This study aims to propose an alternative method to decontaminate 18F-FDG by using graphene oxide (GO). GO was synthesised using the Hummers method while the physical morphology was analysed using a field emission scanning electron microscope (FESEM). 18F-FDG adsorption efficiency rate using GO nanolayers was analysed based on the kinetic study of the GO:18F-FDG mixtures. The chemical adsorbability of the material was analysed via UV–vis spectrophotometer to interlink the microstructures of GO with the sorption affinity interaction. Resultantly, the adsorption rate was effective at a slow decay rate and the optical adsorption of GO with 18F-FDG was dominated by the π → π* plasmon peak, which was near 230 nm. By elucidating the underlining GO special features, an alternative technique to isolate 18F-FDG for the decontamination process was successfully proven.

Safety assessment of graphene oxide and microcystin-LR complex: a toxicological scenario beyond physical mixture

BackgroundNanomaterials have been widely used in electrochemistry, sensors, medicine among others applications, causing its inevitable environmental exposure. A raising question is the “carrier” effect due to unique surface properties of nanomaterials, which may collectively impact the bioavailability, toxicokinetic, distribution and biological effects of classic toxicants. Noteworthy, this aspect of information remains largely unexplored.MethodsHere, we deliberately selected two entities to mimic this scenario. One is graphene oxide (GO), which is made in ton quantity with huge surface-area that provides hydrophilicity and π–π interaction to certain chemicals of unique structures. The other is Microcystin-LR (MCLR), a representative double-bond rich liver-toxic endotoxin widely distributed in aquatic-system. Firstly, the adsorption of GO and MCLR after meeting under environmental conditions was explored, and then we focused on the toxicological effect and related mechanism of GO-MCLR complex on human skin cutin forming cells (HaCaT cells) and normal liver cells (L02 cells).ResultsAbiotically, our study demonstrated that GO could effectively adsorb MCLR through hydrogen bonding and π–π interaction, the oxidation degree of GO-MCLR decreased significantly and surface defect level raised. Compared to GO or MCLR, GO-MCLR was found to induce more remarkable apoptosis and ferroptosis in both HaCaT and L02 cells. The underlying mechanism was that GO-MCLR induced stronger intracellular reactive oxygen species (ROS) and mtROS generation, followed by Fe2+ accumulation, mitochondrial dysfunction and cytoskeletal damage.ConclusionsThese results suggest that the GO-MCLR complex formed by GO adsorption of MCLR may exhibit more toxic effects than the single material, which demonstrates the necessity for assessing nano-toxicant complexity. Our discovery may serve as a new toxicological paradigm in which nanomaterial mediated surface adsorption effects could impact the degree of cytotoxicity and toxicological mechanisms of classic toxins.Graphical