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This study developed a novel nanocomposite by blending Chitosan and Polyvinyl Alcohol (Ch/PVA) with 1% Copper Oxide nanoparticles (CuO NPs), cross-linked using tetraethyl orthosilicate (TEOS). Three Ch/PVA-based nanocomposites were synthesized using CuO, Graphene Oxide (GO), and a CuO&GO combination. The research aimed to assess the nanocomposites' efficacy in removing methyl orange (MO) dye. The X-ray diffraction analysis revealed that the fabricated CuO NPs had a monoclinic structure with an average particle size of 16.35 nm. The distinctive bands at 3222 cm−1 for the Ch/PVA composite were confirmed by Fourier-transform infrared spectroscopy (FT-IR). Scanning Electron Microscopy (SEM) results confirmed the NPs were well distributed throughout the matrix and Thermal gravimetric analysis (TGA) verified the stability of chitosan till 350 °C. The sorption experiments with methyl orange dye were carried out under different pH (2–12), dye concentration (0.025–1.0 mML−1), contact time (0–60 min), and temperature (25–55 °C) to establish the adsorbent at the lab-scale. UV–vis results showed the maximum sorption capacity (72 mM/g) achieved within 10 min with 96% dye removal. The adsorption behavior of nanocomposites was attributed to a physicochemical and monolayer adsorption process. Thermodynamic studies at 328 K confirmed that the adsorption process was spontaneous with ΔG° value − 4.2 KJmol−1. Also, ΔH° and ΔS° were found to be 11.3 and 52.2 KJmol−1 for MO adsorption, respectively. This work paves a new route for developing biodegradable, nontoxic, cost-effective, eco-friendly, and highly efficient adsorbents capable of selectively removing and recycling anionic dyes from wastewater. [ABSTRACT FROM AUTHOR]

In the current study, a chemiresistive SO2 sensor based on a composite of reduced graphene oxide (rGO) and 5, 10, 15, 20-tetra-p-tolyl-21H, 23H-porphine (TPTP) was developed and extensively studied. Improved Hummers methods were used to synthesize graphene oxide (GO), and a thermally heating bottom-up approach was used to reduce GO to rGO. Gold electrodes were thermally coated on the transparent sheet using a thermal evaporator. The composite of rGO/TPTP was synthesized using a simple chemical method. Structural, morphological, spectroscopic, electrical, and optical studies were carried out using X-ray diffraction, atomic force microscopy, field emission scanning electron microscopy, Fourier-transfer infrared spectroscopy, Raman spectroscopy, current–voltage, and UV–vis spectroscopy, respectively. The sensing response of rGO/TPTP for various concentrations of sulfur dioxide (SO2) was investigated in chemiresistive modality. The rGO/TPTP composite chemiresistive sensor displayed exceptional performance, with a consistent response spanning 1 ppm to 10 ppm. It exhibited outstanding repeatability, linearity, stability, and boasted an impressive limit of detection (LOD) of 1 ppm. This LOD is significantly lower than the recommended permissible exposure limit (PEL) of 5 ppm set by OSHA (Occupational Safety and Health Administration), USA. The sensor based on the rGO/TPTP composite exhibited a very fast response and recovery time of 33 s. and 27 s. respectively. [ABSTRACT FROM AUTHOR]

This paper experimentally demonstrates a crossed reaction of pure and hybrid graphene oxide (GO)/tantalum dioxide (TaO2) as a volatile organic compound (VOC) absorber in a guided mode resonance (GMR) sensing platform. The proposed GMR platform has a porous TaO2 film as the main guiding layer, allowing for more molecular adsorption and enhanced sensitivity. GO is applied on top as an additional VOC absorber to increase the selectivity. The hybrid sensing mechanism is introduced by varying the concentration of the GO aqueous solution. The experimental results show that the pure TaO2-GMR has a high tendency to adsorb most of the tested VOC molecules, with the resonance wavelength shifting accordingly to the physical properties of the VOCs (molecular weight, vapor pressure, etc). The largest signal appears in the large molecule such as toluene, and its sensitivity is gradually reduced in the hybrid sensors. At the optimum GO concentration of 3 mg/mL, the hybrid GO/TaO2 -GMR is more sensitive to methanol, while the pure GO sensor coated with GO at 5 mg/mL is highly selective to ammonia. The sensing mechanisms are verified using the Density Functional Theory (DFT) to simulate the molecular absorption, along with the measured functional groups measured on the sensor surface by the Fourier transform infrared spectroscopy (FTIR). The crossed reaction of these sensors is further analyzed by means of machine learning, specifically the principal component analysis (PCA) method and decision tree algorithm. The results show that this sensor is a promising candidate for quantitative and qualitative VOCs detection in sensor array platform. [ABSTRACT FROM AUTHOR]

Peripheral demyelinating diseases entail damage to axons and Schwann cells in the peripheral nervous system. Because of poor prognosis and lack of a cure, this group of diseases has a global impact. The primary underlying cause of these diseases involves the inability of Schwann cells to remyelinate the damaged insulating myelin around axons, resulting in neuronal death over time. In the past decade, extensive research has been directed in the direction of Schwann cells focusing on their physiological and neuroprotective effects on the neurons in the peripheral nervous system. One cause of dysregulation in the remyelinating function of Schwann cells has been associated with oxidative stress. Tissue-engineered biodegradable scaffolds that can stimulate remyelination response in Schwann cells have been proposed as a potential treatment strategy for peripheral demyelinating diseases. However, strategies developed to date primarily focussed on either remyelination or oxidative stress in isolation. Here, we have developed a multifunctional nanofibrous scaffold with material and biochemical cues to tackle both remyelination and oxidative stress in one matrix. We developed a nanofibrous scaffold using polycaprolactone (PCL) as a foundation loaded with antioxidant graphene oxide (GO) and coated this bioscaffold with Schwann cell acellular matrix. In vitro studies revealed both antioxidant and remyelination properties of the developed bioscaffold. Based on the results, the developed multifunctional bioscaffold approach can be a promising biomaterial approach for treating demyelinating diseases. [ABSTRACT FROM AUTHOR]

The widespread production and application of graphene oxide (GO) may lead to its dispersion throughout natural water systems, with potential negative effects on living organisms and the ecological environment. This study used gypsum (G) as an adsorbent and examined different conditions (pH, adsorbent dosage, GO initial concentration) for the removal effect of GO by G. The results showed the best adsorption effect for a solution pH of 8.0, gypsum dosage of 60 mg, initial GO concentration of 80 mg·L−1, and temperature of 303 K; at this time, the maximum removal rate of graphene oxide by gypsum was 93.3%. It could be obtained by isotherm and thermodynamic analysis that the GO adsorption by gypsum conforms to the Langmuir isotherm model, it does not easily occur in high-temperature environments, and is a spontaneous exothermic process. In addition, experiments such as SEM, AFM, TGA, XRD, XPS, FTIR, Raman, and Zeta were used to adsorb graphene oxide by gypsum composites (G/GO), through which the mineral interactions with graphene oxides were microscopically characterized. The impact on the adsorption properties of contaminants provides new insights into contaminant removal by gypsum. [ABSTRACT FROM AUTHOR]

The detection of pollutant and toxic gases has attracted extensive attention due to the growing environmental issues. In the present investigation, free-based tetraphenyl porphyrin (TPP) and iron tetraphenyl porphyrin (FeTPP) are used to functionalize thermally reduced graphene oxide (rGO) and further used for the detection of carbon monoxide (CO). TPP and FeTPP functionalized rGO (FeTPP@rGO) sensors are fabricated on a glass substrate with thermally coated copper electrodes. The materials are characterized with X-ray diffraction (XRD), Fourier transforms infrared (FTIR) spectroscopy, Raman spectroscopy, UV–visible spectroscopy, atomic force microscopy, scanning electron microscopy, and energy dispersive spectroscopy. The current–voltage (I–V) characteristics have also been studied to demonstrate the operation of the device. In addition, the FeTPP@rGO device shows high sensitivity toward the detection of CO. By testing in the chemiresistive sensing modality, the as-fabricated device shows good response and recovery of 60 s and 120 s, respectively, with a low detection limit of 2.5 ppm. [ABSTRACT FROM AUTHOR]

This study examined hybrid nanofluids of graphene nanoplatelets (GNP) and graphene oxide (GO) in terms of their stability and performance as a working fluid in a flat plate solar thermal collector. Instead of functionalisation, this experiment utilises the synergetic effect of GO, which stabilises GNP nanofluids by acting like an amphiphilic surfactant. Experimental results found that stability is significantly improved with a sufficiently high concentration of GO. Stability improved as the proportion of GO was increased. In particular, the sample with an equal 50:50 ratio of GNP and GO showed good stability in sedimentation measurements, retaining over 90% of its concentration over one month. Stability was also measured under working pipe flow conditions in a solar collector test rig. This type of data has not previously been reported in the literature. Measurement of the change in concentration showed that in addition to sedimentation, concentration loss can occur via an alternative mechanism: deposition of the nanoparticles inside the pipes. The pristine GNP sample lost over 80% of its concentration over one day of running in the test rig, despite showing moderate stability over one month under still conditions. This shows that measurement of stability in still conditions does not fully describe the stability of nanofluids intended to be working fluids in heat transfer. The sample with a 50:50 ratio of GNP and GO retained around 66% of its concentration over five days of running in the test rig, and the concentration seemed to stabilise, reaching equilibrium, implying no further decreases. Viscosity measurements showed a small increase. Despite the moderately encouraging stability results, however, solar collector testing showed no discernible change in heat transfer performance when using nanofluids compared to water, making these nanofluids unsuitable for this particular flat plate solar collector design. [ABSTRACT FROM AUTHOR]

Heavy metal ion (HMI) in wastewater is a kind of resource that is wrongly placed. Recovery of heavy metal from lead-acid wastewater desires efficient and reusable functional materials. In this paper, graphene oxide-like with diazanyl groups (GOLA) was synthesized by a nucleophilic substitution reaction of graphene oxide-like with hydroxyl groups (GOLH) with diazane. GOLA exhibited good stability and recyclability in wastewater. The maximal adsorption capacity (qmax) values of GOLA for Pb(II), Cd(II), Cu(II), Ni(II), and Cr(III) ions were 505.80, 401.99, 83.48, 82.29, and 147.77 mg/g, respectively. The equilibrium time of GOLA adsorbing HMIs was 20 min. GOLA was employed to recover lead ions from lead-acid wastewater to give Pb(OH)2 and reusable water. Therefore, this paper provides a useful method of recycling lead from lead-acid wastewater. [ABSTRACT FROM AUTHOR]

In this short review, the nanofluids based on graphene and graphene derivatives are discussed in terms of thermophysical properties. Regular heat transfer fluids as water, ethylene glycol, mixtures of those two as well as oils, ionic liquids, or other glycols are widely used in most of the cooling and heating applications. Nevertheless, nanoparticle-enhanced fluids are coming to the forefront of industrial applications, but the research is still ongoing in order to propose a better and viable alternative, with higher convection coefficients. On the other hand, carbon-based materials have a very high thermal conductivity and are the best candidates for a higher conductive new fluid. This particular overview implies the use of graphene and its derivatives (graphene nanoplatelets, graphene oxide, reduced graphene oxide etc.) as a base for nanofluids development. As a conclusion, thermal conductivity is increased up to 30 % for low nanoparticle loading, while the main drawback is the large increase in viscosity. Specific heat and density are not methodically studied and this is a disadvantage. Another observation derived from state of the art review is that coordinated studies are not noticed. [ABSTRACT FROM AUTHOR]

In recent years, the treatment of water pollution has been a challenging and far-reaching topic. In order to improve the adsorption performance of polyvinyl alcohol nanofibers, a new nano-adsorbent graphene oxide was introduced into them in this work. The water resistance and stability of nanofibers were improved by crosslinking glutaraldehyde. The introduction of GO greatly increased the adsorption of Cu2+, methylene blue (MB) and Congo red (CR). The adsorption kinetics and isotherm analysis of the PVA/GO nanofiber film during the adsorption process showed that the adsorption of Cu2+ and MB by PVA/GO nanofiber film was mainly chemical adsorption, while the adsorption of CR was mainly physical adsorption. The adsorption process of PVA/GO nanofiber film on Cu2+ was in line with the Langmuir isothermal adsorption model, that is, single molecular layer adsorption, the distribution of adsorption active sites was relatively uniform, and the increasing temperature was more conducive to the adsorption of Cu2+. [ABSTRACT FROM AUTHOR]

The compound parabolic collector (CPC) with pulsating heat pipe (PHP) is developed for enhance the heat transfer rate, thermal efficiency and heat losses, and so forth. and working fluid plays a major role in this process. The thermal resistance, temperature, and thermal efficiency have been experimented with under different conditions, and heating periods were analyzed. In this, cobalt oxide (Co3O4) and graphene oxide (GO) added distilled water (DW) is used as the working fluid in the filing ratio of 50%. Bald eagle search optimization (BES) algorithm is used for optimizing the experimented values, and the better‐optimized values are used for hybrid BES based deep belief network (DBN) prediction. The maximum temperature obtained for experiment and optimization is 65 and 65.16161°C. 59% of thermal efficiency was obtained as maximum for experimentation, and 59.1542% of thermal efficiency was obtained as maximum for optimization. The maximum thermal resistance obtained for experimentation and optimization is 0.08 and 0.06938°C/W. In this, optimized outputs performed well than the experimental values. Besides, the hybrid DBN based BES algorithm is performed based on the optimized performances to predict the temperature, thermal efficiency and thermal resistance. Further, predicted outcomes are compared with the non‐hybrid neural networks such as DBN, CNN and ANN. DBN‐BES depicts low error values than the non‐hybrid neural networks. Overall, the proposed hybrid solar collector model and the hybrid nanoparticles added water helps to enhance the thermal characteristics with minimum heat loss. [ABSTRACT FROM AUTHOR]

Polydopamine-Functionalized graphene oxide (PDA-GO) was used to form Polyvinyl Alcohol/Chitosan/PDA-GO (PVA/CS/PDA-GO) hydrogels. FTIR, TGA and SEM investigation showed that PDA had been successfully loaded on graphene oxide nanosheets. Adsorption of metal ions onto the novel PVA/CS/PDA-GO hydrogel beads with variations in pH, contact time, initial metal concentration and temperature had been investigated. Adsorption data were well accurately described by Langmuir isotherm and pseudo-second-order kinetic model at the optimum pH 5.5. The maximum adsorption capacities of the PVA/CS/PDA-GO were 210.94 mg·g−1, 236.20 mg·g−1 and 214.98 mg·g−1 for Cu(II), Pb(II) and Cd(II) ions with 40 C, respectively. Meanwhile, desorption efficiency and reusability of the adsorbents were assessed on basis of six consecutive adsorption-desorption cycles. This work provides a simple and environmentally friendly method to obtain the PVA/CS/PDA-GO hydrogel beads, which really would be a potential recyclable adsorbent for removal of hazardous metal ions in waste water. [ABSTRACT FROM AUTHOR]

A novel chitosan-humic acid-graphene oxide (Cts-HA-GO) composite was produced and tested to remove hexavalent chromium (Cr(VI)) during the adsorption process. The percentage adsorption was 85.28% by using 200 ppm Cr(VI) and 2 g/L composite. Four hours of contact time was enough to remove Cr(VI) from the aquatic medium. The extent of adsorption of Cr(VI) on the surface of Cts-HA-GO composite was examined on the basis of increasing quantity of the composite. The functional group characterization and morphology of composite was characterized using scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. After reaching the equilibrium, the residual concentration of the Cr(VI) solution was measured with an UV-visible spectrophotometer. The results showed that the adsorption behaviour was in accordance with the Langmuir isotherm model, and the maximum adsorption capacity of Cr(VI) determined by using this model was 83.64 mg/g at the pH of 2. A pseudo-second-order model equation has justified the equilibrium between Cr(VI) and the composite for the kinetic studies. [ABSTRACT FROM AUTHOR]