Narrow Results

This study investigates the synthesis and characterization of graphene oxide (GO) and its reduced form, reduced graphene oxide (rGO), focusing on their structural, physicochemical and electrochemical properties. Graphene oxide was synthesized from graphite flakes using the modified Hummer’s method, and hydrothermal reduction with ascorbic acid, which was employed to convert GO into rGO, forming a two-dimensional structure with a high surface area. The structural transformations were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM), which revealed a significant reduction in interlayer spacing and restoration of the $s{p}^2$ hybridized carbon network in rGO, confirming the successful reduction of GO. Chemical modifications were characterized through Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy and X-ray photoelectron spectroscopy (XPS). These techniques demonstrated a marked decrease in oxygen-containing functional groups in rGO, indicating effective reduction and restoration of graphitic structure. Electrochemical studies using cyclic voltammetry demonstrated that rGO-modified carbon paste electrodes (rGO/MCPE) offer superior sensitivity and enhanced electron transfer efficiency. The effects of scan rate, concentration and pH were also evaluated, underscoring its potential for high-sensitivity detection applications. These findings highlight the potential applications of GO and rGO in electrochemical sensors, particularly for detecting biomolecules like serotonin, as well as in energy storage devices such as supercapacitors and batteries, where their high surface area and conductivity offer significant advantages.

Polymer nanocomposite is commonly used to develop structural components of space, aircraft, biomedical, sensor, automobile, and battery sector applications. It remarkably substitutes the heavyweight metallic and nonmetallic engineering materials. The machining principles of polymer nanocomposites are intensely different and complex from traditional metals and alloys. The nonhomogeneity, abrasive, and anisotropic nature differs its machining aspect from conventional metallic materials. This investigation aims to execute the CNC drilling of modified nanocomposite using Graphene–carbon (G-C) @ epoxy matrix. The process constraints, namely, cutting speed (S), feed (F), and wt.% of graphene oxide (GO) vary up to three levels and are designed according to the response surface methodology (RSM) array. The nonlinear model is created to predict surface roughness (Ra) and delamination (Fd) on regression analysis. It has been found that the average error for Ra is 0.94% and for Fd it is 3.27%, which is acceptable in model predictions. The metaheuristics-based evolutionary Dragonfly algorithm (DA) evaluated the optimal parametric condition. The optimal setting prediction for the DA is observed as cutting speed (S)-37.68m/min, feed (F)-80mm/min, and wt.% of graphene oxide (GO)-1%. This algorithm demonstrates a higher application potential than the previous efforts in controlling Ra and Fd values. Both the drilling response values are found to be minimized when the cutting speed increases and the feed decreases. The best fitness value for the DA is 1.626 for surface roughness and 5.086 for delamination. This study agreed with the prediction model’s outcomes and the process parameters’ optimal condition. The defects generated during the sample drilling, such as fiber pull out, uncut/burr, and fiber breakage, were examined using FE-SEM analysis. The optimal findings of the DA module significantly controlled the damages during machining.

The latest addition to the nanocarbon family, graphene, has been proclaimed to be the material of the century. Its peculiar band structure, extraordinary thermal and electronic conductance and room temperature quantum Hall effect have all been used for various applications in diverse fields ranging from catalysis to electronics. The difficulty to synthesize graphene in bulk quantities was a limiting factor of it being utilized in several fields. Advent of chemical processes and self-assembly approaches for the synthesis of graphene analogues have opened-up new avenues for graphene based materials. The high surface area and rich abundance of functional groups present make chemically synthesized graphene (generally known as graphene oxide (GO) and reduced graphene oxide (RGO) or chemically converted graphene) an attracting candidate in biotechnology and environmental remediation. By functionalizing graphene with specific molecules, the properties of graphene can be tuned to suite applications such as sensing, drug delivery or cellular imaging. Graphene with its high surface area can act as a good adsorbent for pollutant removal. Graphene either alone or in combination with other materials can be used for the degradation or removal of a large variety of contaminants through several methods. In this review some of the relevant efforts undertaken to utilize graphene in biology, sensing and water purification are described. Most recent efforts have been given precedence over older works, although certain specific important examples of the past are also mentioned.

Cross-linked polyvinyl alcohol (PVA) graphene oxide (GO) nanocomposites were prepared by simple solution-mixing route and characterized by Raman, UV–visible and fourier transform infrared (FT-IR) spectroscopy analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The XRD pattern and SEM analysis showed significant changes in the nanocomposite structures, and the FT-IR spectroscopy results confirmed the chemical interaction between the GO filler and the PVA matrix. After these morphological characterizations, PVA-GO-based diodes were fabricated and their electrical properties were characterized using current–voltage (I–V) and impedance-voltage-frequency (Z-V-f) measurements at room temperature. Semilogarithmic I–V characteristics of diode showed a good rectifier behavior. The values of C and G/$\omega$ increased with decreasing frequency due to the surface/interface states (N${}_{\mathrm{\text{ss}}}$) which depend on the relaxation time and the frequency of the signal. The voltage, dependent profiles of N${}_{\mathrm{\text{ss}}}$ and series resistance (R${}_{\mathrm{\text{s}}}$) were obtained from the methods of high-low frequency capacitance and Nicollian and Brews, respectively. The obtained values of N${}_{\mathrm{\text{ss}}}$ and R${}_{\mathrm{\text{s}}}$ were attributed to the use of cross-linked PVA-GO interlayer at the Au/n-Si interface.

Graphene has been considered one of the most important materials for many applications due to its unique electronic structure, physical and chemical properties. Graphite flakes are the main source of graphene oxide which can be transformed to graphene after reduction. The effect of irradiation on graphene oxide has been rarely studied, only few studies dealing with the irradiation of graphene oxide with gamma radiation were reported. The effect of irradiation of graphene oxide with gamma ray doses (low linear energy transfer) has been previously studied. It was found that there are no changes in the crystalline structure of graphene oxide after irradiation. Graphene oxide was prepared by modified Hummer’s method. The scanning electron microscopy image of the obtained sample suggests the presence of both single and multilayer graphene oxide sheets. The structural measurements for the graphene oxide samples with high linear energy transfers were carried out after irradiations with different doses of alpha particle (9.30–479.90 Gy). The effect of irradiation on oxygen functional groups of graphene oxide was followed by Fourier transforms infra-red spectrometer. Moreover, the irradiation effect on the lamellar space of graphene oxide layers was measured by X-ray diffraction. It was found that the d-spacing of graphene oxide was decreased after alpha particles irradiation with different doses. The effect of irradiation on dielectric constant and conductivity of graphene oxide samples was measured in the frequency range (200 Hz–1.00 MHz). The dielectric measurements show less dependence on irradiation doses. The graphene oxide sample can be used as radiation dosimeter for $\alpha$-particles in the range of the low irradiation doses.

Emerging memory technologies promise new memories to store more data at less cost. On the other hand, the scaling of silicon-based chips approached its physical limits. Nonvolatile memory technologies, such as resistive random-access memory (RRAM), are trying to solve this problem. The fundamental study in RRAM devices still needs to be moved further. In this regard, conduction mechanism of RRAM is focused in this study. The RRAM conductance varies considerably depending on the material used in the dielectric layer and selection of electrodes. To formulate the conductance mechanism, new materials with notable conductivity such as graphene oxide (GO) sheets has been employed by researchers. In the GO-based RRAM, pristine of GO due to the presence of sp³-hybridized oxygen functional groups(hydroxyl) leads to electrically insulating layers in the device. However, by applying the voltage, the conductive path can be formed with the redox of GO layer in to graphene. This phenomenon is known as RRAM set process which can be explained due to the conversion of sp³ to sp² oxygen functionalities, which make the RRAM to move in to the ON state. Also, in this paper, variation of the ON state resistance by the voltage in the nondegenerate mode is described and the reset process by degeneracy variation is reported.

Graphite oxide was prepared by Hummers method, then it was obtained by ultrasound. Finally, graphene was prepared by using hydrazine hydrate as reducing agent. We can get the influences of oxidation time on the graphene structure by different reacting times. Ultrasonication can reduce the aggregation of graphene efficiently. The morphology and size of graphene were characterized by SEM, TEM, XRD and FTIR. Through this method, we can get high quality graphene which has smooth surface and fewer defects. The longer the oxidation time, the more easier it is to peel and insert functional groups.

In this work, polyvinylidene fluoride (PVDF) and graphene oxide (GO) composite membranes were fabricated using electrospinning technology for particulate matter (PM) filtration. The preparation conditions like GO oxidation time, electrospinning solution composition, and GO content in the composite film, and the basic properties and filtration performance of PVDF–GO films were systematically analyzed. It was found that GO with lamellar structure was of great benefit to endow the membrane with excellent mechanical properties and particle capture capacity. The as-prepared PVDF–GO membranes with GO addition of 0.6 wt.% exhibited the highest tensile strength and PM filtration efficiency. This work demonstrated that blending GO in PVDF is a feasible modification to fabricate an effective PM filtration membrane.

In this paper, 3-aminopropyltriethoxysilane (APS) was applied as an intermediate coupling agent to form chemical bonding between graphene oxide (GO) sheets and silicon substrate (named as APS–GO). Then, trimethoxyphenylsilane coupling agents (TMTES) were assembled on top of APS–GO films as a tail group. The chemical compositions, microstructures, nanotribological and microtribological behaviors were characterized by XPS, WCA, AFM, UMT-2MT and SEM respectively. The results showed that GO sheets were chemically adsorbed on the surface of substrate and chemically reacted with TMTES to form a mulitilayer film. Nanotribological and microtribological results indicated that the prepared APS–GO–TMTES film possessed excellent tribological properties. In addition, friction and wear mechanisms of samples were discussed at the end of this paper.

A sensitive and fast sensor for quantitative detection of organophosphorus pesticides (OPs) is obtained using acetylcholinesterase (AChE) biosensor based on graphene oxide (GO)–chitosan (CS) composite film. This new biosensor is prepared via depositing GO–CS composite film on glassy carbon electrode (GCE) and then assembling AChE on the composite film. The GO–CS composite film shows an excellent biocompatibility with AChE and enhances immobilization efficiency of AChE. GO homogeneously disperses in the GO–CS composite films and exhibits excellent electrocatalytic activity to thiocholine oxidation, which is from acetylthiocholine catalyzed by AChE. The results show that the inhibition of carbaryl/trichlorfon on AChE activity is proportional to the concentration of carbaryl/trichlorfon. The detection of linear range for carbaryl is from 10nM to 100nM and the correlation coefficients of 0.993. The detection limit for carbaryl is calculated to be about 2.5nM. In addition, the detection of linear range for trichlorfon is from 10nM to 60nM and the correlation coefficients of 0.994. The detection limit for trichlorfon is calculated to be about 1.2nM. This biosensor provides a new promising tool for trace organophosphorus pesticide detection.

This study investigated the preparation of graphene oxide from mildly oxidized graphite through ultrasonic exfoliation. Both the original and produced materials were analyzed by ultraviolet–visible spectrophotometer, X-ray diffraction and atomic force microscopy. The results indicated that the exfoliation yield of graphene oxide was proportional to the input ultrasonic energy. In addition, a two-stage exfoliation phenomenon was observed in the exfoliation of mildly oxidized graphite with both ultrasonic homogenizer and cleaner. It also was found that increasing the content of [$O$] in a C–H₂SO₄–[$O$] reaction system was the most simple and direct method to increase the oxidation degree of graphite oxide.

Recent advances in polymer nanocomposites open a wide range of applications in various industrial sectors. Due to their high potential properties, these materials are replacing the usage of metals for many heavier components in automobile industries. In this experimental work, the tribological performance of Graphene oxide (GO) — Polyamide is investigated against pristine polyamide by fabricating gears for the usage in engineering applications. A gear test rig was developed in-house for analysis to study the specific wear rate and temperature gradient at different conditions of load and speeds. The wear resistance of the polyamide gears with the addition of 0.03wt.% of graphene oxide is better than the pristine polyamide gears and the specific wear rate is reduced significantly. The reduced specific wear rate of these polymer nanocomposite gears is attributed to the superior properties of graphene oxide such as High specific surface area, good adhesion properties and enhanced glass transition temperatures. The GO nanocomposite gear seems to be a potential alternative against conventional gears for engineering applications. Finally, the wear mechanisms and the potential of GO-based polyamide nanocomposite gears were proposed tentatively in the development of transmission gears for engineering applications.

Nowadays, the superior properties of carbon-based materials especially nano structural derivation like graphene and graphene oxide (GO) spot light to the researchers. The GO has been suggested as an alternate material in device miniaturization due to its atomic structure. The memristors and nonvolatile memories are settled in these categories as a solution for the scaling limitation problem in the Moor’s law. Therefore, the GO can influence the memristor performance and characteristics. The current–voltage characteristics as the most significant parameter in the memristor design are considered. On the other hand $I$–$V$ characteristic depends on the active layer (GO) bandgap energy in the metal/oxide/metal structure and therefore, needs to be explored. In the GO-based memristor, the bandgap energy can be changed by the percentage of the oxygen groups in comparison to the carbon on graphene sheets. Thus, the other parameters are overstated by the bandgap energy. In the presented work, the energy bandgap of a high epoxy group content of GO sheets is engineered. The opening of the bandgap in the graphene oxide by high epoxy groups content with the ratio of (O/C $=$ 50%) is studied. In other words, the oxygen adsorption effect on the Hamiltonian of the system is explored. For the proposed structure, the bandgap energy is modeled and the acceptable value (approximately equal to 2.799ev for epoxy groups) is obtained. Moreover, the hydroxyl group adsorption effect on the bandgap of the graphene oxide by high content hydroxyl group is considered (approximately equal to 2.647ev for epoxy groups). Consequently, the different absorption energy effects on the bandgap of the GO is participated and the opening bandgap in the range of 2ev to 3ev is obtained. The excitonic effect on the suggested model by epoxy groups and hydroxyl groups is explored and it is realized that the energy levels in the Dirac points of epoxy groups are closer than those of the hydroxyl groups.

Nylon ($N$), Glass-filled nylon (GFN) composites and hybrid graphene oxide blended GFN (GO-GFN) nanocomposites plates were prepared by blending and subsequent injection molding process. Mechanical tests were conducted to study the tensile property, flexural property and hardness of nylon, GFN and GO-GFN system. The fabricated plates were subjected to abrasive wear testing in Pin-on-disc tribometer. The pin used is aluminium oxide (Al₂O₃) ceramic tool. The coefficient of friction, frictional force and loading variations were observed and studied to analyze the susceptibility of nylon, GFN and GO-GFN nanopolymer composites for abrasive wear conditions. This experimental study confirmed the enhancement in the abrasive wear resistance behavior of GO-GFN hybrid nanocomposites.

Graphene oxide (GO) sheet and ultrasonic field (UF) were successfully employed to produce Ni–B/GO and UF–Ni–B/GO composite coatings on Q235 mild steel by electroless plating. The composite coatings’ structure and surface morphology were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Results showed that GO was successfully co-deposited in the Ni–B alloy. Moreover, UF–Ni–B/GO composite coatings have smoother surface and thicker cross-section than others. The microhardness and corrosion resistance of the sample coatings were determined using Vickers hardness tests, Tafel electrochemical tests and electrochemical impedance measurements (EIS) in 3.5wt.% NaCl solution to receive the effect of GO and ultrasonic. The findings indicated that UF–Ni–B/GO exhibited optimum hardness (856HV) and enhanced corrosion resistance (6.38 $\mu$${\text{A cm}}^{-2})$ over the Ni–B and Ni–B/GO coatings. Due to these interesting properties of the coating, it could be used as a protective material in the automotive and aerospace industries for parts of machines that were manipulated in high temperature and corrosive environments.

Reduced graphene oxide (RGO)/TiO₂ nanocomposite coating was synthesized using electrophoretic co-deposition (EPD) of graphene oxide and TiO₂ colloidal suspension. Direct assembly by EPD facilitated the transformation from GO to RGO and resulted in RGO/TiO2 films on Cu substrate. The prepared samples were characterized by X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. The obtained results proved the presence of titania nanoparticles and RGO planes in the nanocomposite coatings and the reduction of GO during EPD process. Methylene blue photodegradation experiments showed that the degradation efficiency and the reduction rate of the contact angle increased in nanocomposite coatings by 12% and 15%, respectively. There is a direct correlation between the amount of RGO in the coating and the improvement of the photocatalytic activity and wettability.

A flexible organic light-emitting device (OLED) was produced using copper nanowire (CuNW) film as anode and Graphene oxide (GO)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) film as anode buffer layer. Compared with other transparent conductive films (TCFs), CuNWs are low cost, easy to fabricate, and compatible with flexible substrates over a large area. Due to these advantages, CuNWs are showing greater and greater promise for the next generation of TCF. Modified by PEDOT:PSS, the conductivity and work function of the CuNW film can be dramatically enhanced. However, PEDOT:PSS is highly acidic and easy to corrode the CuNW film, which will reduce maximum luminous brightness and current efficiency of the OLED. In this paper, GO/PEDOT:PSS was used as anode buffer layer to modify the CuNW anode and the composite transparent electrode exhibited excellent optoelectrical properties. The driving voltage of the OLED with CuNW/PEDOT:PSS is 6.2V, and the maximum luminous brightness is 2737.2cd/m². The driving voltage of the OLED with CuNW/GO/PEDOT:PSS anode was reduced to 5.1V, and the maximum luminous brightness was improved to 3007.4cd/m².

Reduced graphene oxide (rGO) has attracted interest in its potential application in large area photodetectors owing to its ease of manufacture and wideband optical absorbance. Here, we report that thin rGO films produced via vacuum filtration of GO followed by reduction by immersion in L-ascorbic acid are capable of sensing light through a bolometric mechanism. The photoresponse of these rGO thin films can be further enhanced by dropcasting graphene quantum dots (GQDs) on the rGO surface. These GQDs were observed to increase the opacity of the rGO film and hence its absorptivity of light, thereby enabling a significant increase in the photoresponse of the device.

This article describes new control criteria and robust optimization methodology to balance drilling parameters and machining characteristics. Experimentation was performed according to response surface methodology (RSM) using a TiAlN coated SiC tool. The full drilling force signal and cutting parameters tested are categorized into five stages, indicating the drilling tool-workpiece interactions’ different statuses. Principal component analysis (PCA) assigns real response priority weight during the aggregation of conflicting characteristics. The hybrid module of combined compromise solution and PCA (CoCoSo–PCA) is used to decide the optimal parametric setting. It efficiently undertakes a trade-off between minimal thrust ($Th=30.02$N), torque ($T=0.05$Nm) surface roughness ($R_a=1.55\mu$m). A regression model between input parameters and output function was established using RSM quadratic model. The validation experiment shows significant improvement, and the proposed module can be recommended for quality-productivity characteristics control.

Graphite oxide was prepared by improved Hummer’s method. Then the graphene oxide (GO) suspension was obtained through ultrasonication for 1 h. The GO suspension was mixed with sulfur (S) using three different methods (namely sodium polysulfide route, sodium borohydride route, and hydrothermal route) of which two were chemical methods while one was hydrothermal method to make the composite material of reduce GO and sulfur (rGO–S). The electrode of the rGO–S composite was then prepared by making a slurry of active material, carbon black and polyvinylidene fluoride (PVDF). The sample of GO was analyzed using UV–visible and FTIR spectroscopy, while the sample of rGO and S was analyzed using XRD. This confirmed the synthesis of rGO–S for all the three methods. The comparison of all the three methods shows that the chemical methods are time consuming, difficult and toxic while hydrothermal method is easy and friendly.