Study on Antiaging Performance of Graphene Oxide–Modified Guss Asphalt

Thorium carbide to be tested as target material for the production of 225Ac with the ISOL method, was produced via carbothermal reduction of ThO2 nanoparticles by graphite and graphene oxide, respectively. The use of graphene oxide (GO) as carbon source resulted in a reduced reactivity compared to graphite, confirmed by the presence of unreacted ThO2 mainly in the core of the samples. The reacted ThO2 or ThC2–GO showed a faster reactivity in air, mainly observed as ThC2 amorphization. The specific surface area of the ThC2–GO samples was almost doubled compared to ThC2–graphite samples. The effect of these microstructural features was analysed in terms of thermal diffusivity and calculated thermal conductivity that were both reduced in ThC2–GO samples, however the difference with ThC2–graphite samples decreased at increasing temperature. The present study shows that the use of unreduced GO inhibits the solid-state reaction between ThO2 and C; on the other hand, the high reactivity of the ThC2 so produced is expected to be beneficial for the 225Ac production with the ISOL method, affording a high release efficiency. It is expected that the use of reduced GO could represent a good solution for highly efficient ThC2 targets.

In the last decade, along with the increasing use of graphene oxide (GO) in various applications, there is also considerable interest in understanding its effects on human health. Only a few experimental approaches can simulate common routes of exposure, such as ingestion, due to the inherent complexity of the digestive tract. This study presents the synthesis of size-sorted GO of sub-micrometer- or micrometer-sized lateral dimensions, its physicochemical transformations across mouth, gastric, and small intestinal simulated digestions, and its toxicological assessment against a physiologically relevant, in vitro cellular model of the human intestinal epithelium. Results from real-time characterization of the simulated digestas of the gastrointestinal tract using multi-angle laser diffraction and field-emission scanning electron microscopy show that GO agglomerates in the gastric and small intestinal phase. Extensive morphological changes, such as folding, are also observed on GO following simulated digestion. Furthermore, X-ray photoelectron spectroscopy reveals that GO presents covalently bound N-containing groups on its surface. It is shown that the GO employed in this study undergoes reduction. Toxicological assessment of the GO small intestinal digesta over 24 h does not point to acute cytotoxicity, and examination of the intestinal epithelium under electron microscopy does not reveal histological alterations. Both sub-micrometer- and micrometer-sized GO variants elicit a 20% statistically significant increase in reactive oxygen species generation compared to the untreated control after a 6 h exposure.

Nanomaterials have received increased concentration in the field of civil engineering, as their incorporation can effectively modify the mechanical and transport properties of cementitious composites. In this study, to understand the effect of graphene oxide (GO) nanoparticles on the durability and mechanical properties of cementitious composites serving underwater, mortars incorporated with GO were taken for study. To match the real circumstance, all specimens were immersed directly in a flowing river for three years, and their transport properties, mechanical properties and microstructure before, and after, river experience were studied separately. The results showed that the incorporation of GO could reduce both early-age permeation coefficient and later-age chloride migration coefficient of mortar specimens. The average porosities of mortars could be reduced by the range of 3.37–11% with GO incorporation. Moreover, through a novel dual-scan method, GO incorporation was confirmed effective in enhancing both the leaching and cracking resistance. Furthermore, the compressive strengths, flexural strengths and splitting tensile strengths could be improved by the range of 4.37–9.82%, 7.78–22.33%, 8.14–28.73%, respectively with GO incorporation, and the tested mechanical strengths for GO-incorporated mortar after three-year river experience could be retained to a higher extent. Finally, based on durability and mechanical properties, the optimum mix proportion of GO was determined to be 0.06 wt.% in this study. The work presented here is of high reference value for the designing of marine infrastructure and can help promote the application of nanomaterials in civil engineering.

Chemical instability of graphene oxide following exposure to highly reactive radicals in advanced oxidation processes

Since late 20th century, the drawbacks of pollution became obvious which increases the demand for environmental friendly and ecological approaches in all disciplines. Not only using environment friendly materials and procedures, but also detecting any pollution, and potential solutions are also common area of current research. SO2, one of the significant topics in waste management, is reported to cause acidic rain. To abolish SO2 waste, excess temperature is required. The current efforts are to develop materials that can remove SO2 at comparatively low temperatures. The aim of this study is to examine a potential use of graphene oxide (GO) fibers and composite polyvinyl alcohol (PVA) incorporated GO fibers in SO2 filters. So as to observe the effect of PVA incorporation on composite fiber properties, PVA incorporated GO fibers and neat GO fibers were prepared. GO fibers were prepared with modified Hummers method followed by wet spinning through three coagulation baths. For composite fiber formation, 10% PVA was added to coagulation bath three. So formed fiber morphologies were analyzed with SEM, AFM and BET. Electrical conductivities were calculated from electrical resistances measured with conductivity tester. The SO2 adsorption and desorption properties were measured in a quartz reactor. PVA addition did not have a significant effect on electrical conductivity whereas increases the SO2 adsorption capacity and reduces the surface roughness, pore size, pore volume and surface area.

Graphene oxide as novel vaccine adjuvant

A comparison was performed between the use of graphene oxide (GO) and reduced graphene oxide (rGO) as a hole extraction layer (HEL) in organic photovoltaic (OPV) cells with poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester. Hydrazine hydrate (HYD) and the thermal method (Thermal) were adopted to change the GO to rGO. The GO HEL was deposited on an indium tin oxide electrode by spin coating, followed by the reduction process to form the rGO HELs. The success of the reduction processes was confirmed by X-ray diffraction, Raman spectroscopy, X-ray photoemission spectroscopy, transmittance, and 2-point probe method. The OPV cell with the GO (-3 nm) HEL exhibits an increased power conversion efficiency (PCE) as high as 2.5% under 100 mW/cm2 illumination under air mass conditions, which is higher than that of the OPV cell without HEL, viz. 1.78%. However, the PCE of the OPV cell with rGO HEL is not high as the values of 1.8% for the HYD-rGO and 1.9% for the Thermal-rGO. The ultraviolet photoemission spectroscopy results showed that the work function of GO was 4.7 eV, but those of HYD-rGO and Thermal-rGO were 4.2 eV and 4.5 eV, respectively. Therefore, it is considered that GO is adequate to extract the holes from the active layer, but HYD-rGO and Thermal-rGO are not appropriate to use as HELs in OPV cells from the viewpoint of the energy alignment.

Label free electrochemical sensor for Pb2+ based on graphene oxide mediated deposition of silver nanoparticles

Wear and corrosion resistance enhancement of chromium surfaces through graphene oxide coating

The potential wide use of graphene oxide in various fields results in the possibility of its dispersion throughout natural water systems, with a negative impact on organisms and ecosystems. This study evaluated the removal of graphene oxide (GO) from water by fly ash (FA). The effects of various conditions (including the initial concentration of graphene oxide, the pH of the initial solution, the amount of absorbent, and temperature) on the removal rate of GO were investigated in detail. The results show that the maximum removal rate of graphene oxide by fly ash is 93%; the isotherm adsorption process conforms to a Langmuir model; the adsorption reaction is a spontaneous exothermic process. Under optimal conditions, the pH of the solution was adjusted to 6, the amount of fly ash was 5 mg, the initial concentration of GO was 60 mg·L-1, and the temperature was 303 K. Using X-ray diffraction (XRD), Raman spectroscopy (Raman), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscopy (TEM), Zeta potential and X-ray electron spectroscopy (XPS), the adsorption mechanism was characterized. The experimental results demonstrate that fly ash is a good material for GO removal from aqueous solution.

The use of graphene oxide (GO) has become widespread due to its advantageous properties for applications in medical devices, including cell scaffolds and sensors. Investigations on the spectroscopic and electrochemical features of nanostructured cell scaffolds may be of interest to design novel scaffolds architectures aimed at understanding their interactions with healthy and cancer cells. In this study, we investigated the interactions between liver cancer cells and two GO‐containing scaffold platforms, namely: cells membrane models containing GO in the form of Langmuir–Blodgett films, and GO‐modified biodegradable polycaprolactone nanofibers. Sum‐frequency generation spectroscopy revealed the presence and formation of an expanded phospholipid monolayer underneath GO, while scanning electron microscopy images revealed the morphology of the cells on the different surfaces. Electrochemical impedance spectroscopy was employed to evaluate the charge transfer resistance in different nanostructured scaffolds containing liver cancer cells. The nanosystems developed here can be applied to study the interactions between cells on polymer nanofibers and Langmuir–Blodgett films modified with GO for regenerative medicine.

A nanosorbent composed of magnetite nanoparticles, graphene oxide and a molecularly imprinted polymer (Fe3O4@SiO2-NH2/GOx/MIP) was synthesized and applied to simultaneous extraction of cephalexin, cefazolin and cefoperazone from milk. The use of magnetite nanoparticles enables fast extraction by using an external magnet. The use of graphene oxide increases extraction affinity, and the MIP improves selectivity. Extraction efficiency was optimized by investigating the effects of the template-to-monomer and cross-linker ratios, the desorption condition, extraction time, salting-out effect, stirring rate, sample volume and amount of adsorbent. The cephalosporins were quantified by using HPLC. Under optimum condition, the linear range of the method extends from 2.5 to 100μgL-1 for cephalexin and cefazolin, and from 5.0 to 100μgL-1 for cefoperazone. The limits of detection are 2.5μgL-1 for cephalexin and cefazolin, and 5μgL-1 for cefoperazone. The adsorbent was applied to the extraction of cephalosporins from milk, with recoveries in a range from 80.2 to 111.7% and with RSDs of <8.5%. Graphical abstractSchematic representation of ananocomposite adsorbent consistingof magnetic molecularly imprinted polymer and graphene oxide (GOx). Integrating of magnetite nanoparticles, GOx and high specificity of MIP, the method exhibited a rapid, high extraction efficiency, good selectivity for multi-residue analysis of cephalosporins.

In the present study, a novel quantitative method, namely solid phase extraction, was applied to extract vitamin B12 from pharmaceutical formulations. The technique involves the use of graphene oxide (GO) as an efficient adsorbent for solid-phase extraction of vitamin B12. Collection of GO from aqueous solution was simply achieved by applying filtration assembly. The extracted analyte was directly analyzed by using X-ray fluorescence (XRF) spectroscopy. Factors affecting the extraction efficiency were investigated and optimized. Under the optimum conditions, enhancement factor of 46, linear dynamic range of 25–1000 µg l−1 with correlation of determination (R2 = 0.998) and limit of detection of 20 µg l−1 were obtained for vitamin B12. The percent relative standard deviation based on three-replicate determination was less than 8.1%. The method was successfully applied for extraction and determination of vitamin B12 in different types of pharmaceutical samples such as multivitamin tablet, effervescent tablet and injection sample. The results showed that the proposed method based on GO was a simple, accurate, and highly efficient approach for analysis of vitamin B12. Copyright © 2014 John Wiley & Sons, Ltd.

The article reports an aptamer based assay for cocaine by employing graphene oxide and exonuclease III-assisted signal amplification. It is based on the following scheme and experimental steps: (1) Exo III can digest dsDNA with blunt or recessed 3-terminus, but it has limited activity to ssDNA or dsDNA with protruding 3-terminus; (2) GO can absorb the FAM-labeled ssDNA probe and quench the fluorescence of probe, while the affinity between FAM-labeled mononucleotide and GO is negligible; (3) Cocaine aptamer can be split into two flexible ssDNA pieces (Probe 1 and Probe 2) without significant perturbation of cocaine-binding abilities; (4) The triple complex consisting of Probe 1, Probe 2 and cocaine can be digested by Exo III with the similar efficiency as normal dsDNA. Cocaine aptamer is split into two flexible ssDNA pieces (Probe 2 and 3′-FAM-labeled Probe 1). Cocaine can mediate the cocaine aptamer fragments forming a triplex. The triple complex has unique characteristic with 3′-FAM-labeled blunt end at the Probe 1 and 3′-overhang end at Probe 2. If exonuclease III is added, it will catalyze the stepwise removal of fluorescein (FAM) labeled mononucleotides from the 3-hydroxy termini of the special triplex complex, resulting in liberation of cocaine. The cocaine released in this step can produce a new cleavage cycle, thereby leading to target recycling. Through such a cyclic bound-hydrolysis process, small amounts of cocaine can induce the cleavage of a large number of FAM-labeled probe 1. The cleaved FAM-labeled mononucleotides are not adsorbed on the surface of graphene oxide (GO), so a strong fluorescence signal enhancement is observed as the cocaine triggers enzymatic digestion. Under optimized conditions, the assay allows cocaine to be detected in the 1 to 500 nM concentration range with a detection limit of 0.1 nM. The method was applied to the determination of cocaine in spiked human plasma, with recoveries ranging from 92.0 to 111.8 % and RSD of <12.8 %.

Forward osmosis (FO) is an emerging membrane process with potential applications in the treatment of highly fouling feedwaters. However, biofouling, the adhesion of microorganisms to the membrane and the subsequent formation of biofilms, remains a major limitation since antifouling membrane modifications offer limited protection against biofouling. In this study, we evaluated the use of graphene oxide (GO) for biofouling mitigation in FO. GO functionalization of thin-film composite membranes (GO-TFC) increased the surface hydrophilicity and imparted antimicrobial activity to the membrane without altering its transport properties. After 1 h of contact time, deposition and viability of Pseudomonas aeruginosa cells on GO-TFC were reduced by 36% and 30%, respectively, compared to pristine membranes. When GO-TFC membranes were tested for treatment of an artificial secondary wastewater supplemented with P. aeruginosa, membrane biofouling was reduced by 50% after 24 h of operation. This biofouling resistance is attributed to the reduced accumulation of microbial biomass on GO-TFC compared to pristine membranes. In addition, confocal microscopy demonstrated that cells deposited on the membrane surface are inactivated, resulting in a layer of dead cells on GO-TFC that limit biofilm formation. These findings highlight the potential of GO to be used for biofouling mitigation in FO.