Bridging biomimetic and bioenergetics scaffold: Cellulose-graphene oxide-arginine functionalized aerogel for stem cell-mediated cartilage repair

The avascular nature of cartilage tissue limits inherent regenerative capacity to counter any damage and this has become a substantial burden to the health of individuals. As a result, there is a high demand to repair and regenerate cartilage. Existing tissue engineering approaches for cartilage regeneration typically produce either microporous or nano-fibrous scaffolds lacking the desired biological outcome due to lack of biomimetic dual architecture of microporous construct with nano-fibrous interconnected structures like the native cartilage. Most of these scaffolds also fail to suppress ROS generation and provide sustained bioenergetics to cells, resulting in the loss of metabolic activity under avascular microenvironment of cartilage. A dual architecture microporous construct with nano-fibrous interconnected network of cellulose aerogel reinforced with arginine-coated graphene oxide (CNF-GO-Arg aerogel) was developed for cartilage regeneration. The designed dual-architectured CNF-GO-Arg aerogel using dual ice templating assembly demonstrates 80 % strain recovery ability under compression. The release of Arginine from CNF-GO-Arg aerogel supported 41 % reduction in intracellular ROS activity and promoted chondrogenic differentiation of hMSCs by shifting mitochondrial bioenergetics towards oxidative phosphorylation indicated by JC-1 dye staining. Overall developed CNF-GO-Arg aerogel provided multifunctionality via biomimetic morphology, cellular bioenergetics, and suppressed ROS generation to address the need for regeneration of cartilage.

Teicoplanin-Decorated Reduced Graphene Oxide Incorporated Silk Protein Hybrid Hydrogel for Accelerating Infectious Diabetic Wound Healing and Preventing Diabetic Foot Osteomyelitis

Developing hybrid hydrogel dressings with anti-inflammatory, antioxidant, angiogenetic, and antibiofilm activities with higher bone tissue penetrability to accelerate diabetic wound healing and prevent diabetic foot osteomyelitis (DFO) is highly desirable in managing diabetic wounds. Herein, the glycopeptide teicoplanin is used for the first time as a green reductant to chemically reduce graphene oxide (GO). The resulting teicoplanin-decorated reduced graphene oxide (rGO) is incorporated into a mixture of silk proteins (SP) and crosslinked with genipin to yield a physicochemically crosslinked rGO-SP hybrid hydrogel. This hybrid hydrogel exhibits high porosity, self-healing, shear-induced thinning, increased cell proliferation and migration, and mechanical properties suitable for tissue engineering. Moreover, the hybrid hydrogel eradicates bacterial biofilms with a high penetrability index in agar and hydroxyapatite disks covered with biofilms, mimicking bone tissue. In vivo, the hybrid hydrogel accelerates the healing of noninfected wounds in a diabetic rat and infected wounds in a diabetic mouse by upregulating anti-inflammatory cytokines and downregulating matrix metalloproteinase-9, promoting M2 macrophage polarization and angiogenesis. The implantation of hybrid hydrogel into the infected site of mouse tibia improves bone regeneration. Hence, the rGO-SP hybrid hydrogel can be a promising wound dressing for treating infectious diabetic wounds, providing a further advantage in preventing DFO.

A suitably fabricated ternary nanocomposite (Cu-CuO@rGO-SiO2) as a sustainable and common heterogeneous catalyst for C-S, C-O and C-N coupling reactions

A hybrid composite based on π-electron rich reduced graphene oxide (rGO) and mesoporous silica (SiO2) was prepared and decorated with copper species to afford a ternary nanocomposite material (Cu-CuO@rGO-SiO2). This copper-based nanocomposite was successfully used as a robust and multi-tasking heterogeneous catalyst for most common cross-coupling reactions (e.g. C-S, C-O and C-N coupling). A broad range of catalytic activities are believed to be originated from the synergism of different co-existing copper species (Cu(0) and CuO) and facile charge transfer from the metal ions towards rGO-SiO2 matrices, as established from XPS and other studies.

Magnetic graphene derivates for efficient herbicide removal from aqueous solution through adsorption

2,4-Dichlorophenoxyacetic acid (2,4-D) is an herbicide and is among the most widely distributed pollutant in the environment and wastewater. Herein is presented a complete comparison of adsorption performance between two different magnetic carbon nanomaterials: graphene oxide (GO) and its reduced form (rGO). Magnetic functionalization was performed employing a coprecipitation method, using only one source of Fe2+, requiring low energy, and potentially allowing the control of the amount of incorporated magnetite. For the first time in literature, a green reduction approach for GO with and without Fe3O4, maintaining the magnetic behavior after the reaction, and an adsorption performance comparison between both carbon nanomaterials are demonstrated. The nanoadsorbents were characterized by FTIR, XRD, Raman, VSM, XPS, and SEM analyses, which demonstrates the successful synthesis of graphene derivate, with different amounts of incorporate magnetite, resulting in distinct magnetization values. The reduction was confirmed by XPS and FTIR techniques. The type of adsorbent reveals that the amount of magnetite on nanomaterial surfaces has significant influence on adsorption capacity and removal efficiency. The procedure demonstrated that the best performance, for magnetic nanocomposites, was obtained by GO∙Fe3O4 1:1 and rGO∙Fe3O4 1:1, presenting values of removal percentage of 70.49 and 91.19%, respectively. The highest adsorption capacity was reached at pH 2.0 for GO∙Fe3O4 1:1 (69.98 mg g-1) and rGO∙Fe3O4 1:1 (89.27 mg g-1), through different interactions: π-π, cation-π, and hydrogen bonds. The adsorption phenomenon exhibited a high dependence on pH, initial concentration of adsorbate, and coexisting ions. Sips and PSO models demonstrate the best adjustment for experimental data, suggesting a heterogeneous surface and different energy sites, respectively. The thermodynamic parameters showed that the process was spontaneous and exothermic. Finally, the nanoadsorbents demonstrated a high efficiency in 2,4-D adsorption even after five adsorption/desorption cycles.

Selective NO2 Gas Sensors Employing Nitrogen- and Boron-Doped and Codoped Reduced Graphene Oxide

In this paper, we develop high-performance gas sensors based on heteroatom-doped and -codoped graphene oxide as a sensing material for the detection of NO2 at trace levels. Graphene oxide (GO) was doped with nitrogen and boron by a chemical method using urea and boric acid as precursors. The prepared samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The obtained results proved the successful reduction of graphene oxide by doping effects, leading to the removal of some oxygen functional groups and restoration of an sp2 carbon structure. New bonds in honeycombs, such as pyridinic, pyrrolic, graphitic, B-C3, B-C2-O, and B-O, were created. Compared to the nondoped GO, the N/B-rGO materials exhibited enhanced responses toward low concentrations of NO2 (<1 ppm) at 100 °C. Particularly, the N-rGO-based device showed the highest sensitivity and lowest limit of detection.

Biomass Pyrolysis-Derived Biochar: A Versatile Precursor for Graphene Synthesis

Graphene, a two-dimensional carbon allotrope with a honeycomb structure, has emerged as a material of immense interest in diverse scientific and technical domains. It is mainly produced from graphite by mechanical, chemical and electrochemical exfoliation. As renewable energy and source utilization increase, including bioenergy from forest and woody residues, processed, among other methods, by pyrolysis treatment, it can be expected that biochar production will increase too. Thus, its useful applications, particularly in obtaining high-added-value products, need to be fully explored. This study aims at presenting a comprehensive analysis derived from experimental data, offering insights into the potential of biomass pyrolysis-derived biochar as a versatile precursor for the controlled synthesis of graphene and its derivatives. This approach comprehended the highest energy output and lowest negative environmental footprint, including the minimization of both toxic gas emissions during processing and heavy metals' presence in the feedstock, toward obtaining biochar suitable to be modified, employing the Hummers and intercalation with persulfate salts methods, aiming at deriving graphene-like materials. Material characterization has revealed that besides morphology and structural features of the original wooden biomass, graphitized structures are present as well, which is proven clearly by Raman and XPS analyses. Electrochemical tests revealed higher conductivity in modified samples, implying their graphene-like nature.

Room-temperature assembled 3D macro-porous Ti3C2Tx/RGO hybrid hydrogel and the application as the self-standing electrode for sodium-ion storage

Assembling two-dimensional (2D) MXene nanosheets into monolithic three-dimensional (3D) structures is an efficient pathway to transfer the nanoscale properties to practical applications. Nevertheless, the majority of the preparation schemes described in the literature are carried out at relatively high temperatures, which inevitably leads to the notorious high-temperature oxidation issue of MXenes. Preparing MXene-based hydrogels at lower temperatures or even room temperature is of great research importance. In this study, we report a novel and efficient room-temperature gelation method for fabricating 3D macro-porous Ti3C2Tx MXene/reduced graphene oxide (RGO) hybrid hydrogels, using anhydrous sodium sulfide (Na2S) as the primary reducing agent and l-cysteine as the auxiliary crosslinker. This room-temperature preparation technique successfully prevents the oxidation issue of MXenes and generates porous aerogels with excellent structural robustness after freeze-drying. As the self-standing anode for sodium-ion storage, the optimized 3D Ti3C2Tx MXene/RGO electrode possesses a specific capacity of 152 mAh/g at 0.1 A/g and good cycling stability with no significant capacity degradation after 500 cycles, which is significantly higher than that of the vacuum-filtered MXene film. This work demonstrates a straightforward room-temperature gelation method for constructing 3D MXene-based hydrogels to avoid the oxidation of MXenes, and casts new insight on the mechanism of the graphene oxide (GO)-assisted gelation.

Adenylate kinase immobilized on graphene oxide impairs progression of human lung carcinoma epithelial cells through adenosinergic pathway

Purinergic signaling, the oldest evolutionary transmitter system, has been increasingly studied as a pivotal target for novel anti-cancer therapies. In the present work, the developed nanobiocatalytic system consisting of adenylate kinase immobilized on graphene oxide (AK-GO) was characterized in terms of its physicochemical and biochemical properties. We put special emphasis on the AK-GO influence on purinergic signaling components, that is, ecto-nucleotides concentration and ecto-enzymes expression and activity in human lung carcinoma epithelial (A549) cells. The immobilization-dependent modification of AK kinetic parameters allowed for the removal of ATP excess while maintaining low ATP concentrations, efficient decrease in adenosine concentration, and control of the nucleotide balance in carcinoma cells. The cyto- and hemocompatibility of developed AK-GO nanobiocatalytic system indicates that it can be successfully harnessed for biomedical applications. In A549 cells treated with AK-GO nanobiocatalytic system, the significantly decreased adenosinergic signaling results in reduction of the proliferation and migration capability of cancer cells. This finding is particularly relevant in regard to AK-GO prospective anti-cancer applications.

Graphene as a nano-delivery vehicle in agriculture - current knowledge and future prospects

Graphene has triggered enormous interest in, and exploration of, its applications in diverse areas of science and technology due to its unique properties. While graphene has displayed great potential as a nano-delivery system for drugs and biomolecules in biomedicine, its application as a nanocarrier in agriculture has only begun to be explored. Conventional fertilizers and agricultural delivery systems have a number of disadvantages, such as: fast release of the active ingredient, low delivery efficiency, rapid degradation and low stability that often leads to their over-application and consequent environmental problems. Advanced nano fertilizers with high carrier efficiency and slow and controlled release are now considered the gold standard for promoting agricultural sustainability while protecting the environment. Graphene's attractive properties include large surface area, chemical stability, mechanical stability, tunable surface chemistry and low toxicity making it a promising material on which to base agricultural delivery systems. Recent research has demonstrated considerable success in the use of graphene for agricultural applications, including its utilization as a delivery vehicle for plant nutrients and crop protection agents, as well as in post-harvest management of crops. This review, therefore, presents a comprehensive overview of the current status of graphene-based nanocarriers in agriculture. Additionally, the review outlines the surface functionalization methods used for effective molecular delivery, various strategies for nano-vehicle design and the underlying features necessary for a graphene-based agro-delivery system. Finally, the review discusses directions for further research in optimization of graphene-based nanocarriers.

Carbonaceous CoCr LDH nanocomposite as a light-responsive sonocatalyst for treatment of a plasticizer-containing water

The carbonous-based nanocomposites of CoCr layered double hydroxide (LDH) with graphene oxide (GO) and reduced graphene oxide (rGO) were prepared. The successful synthesis of the CoCr LDH in hydrotalcite crystalline structure was deduced from the pattern obtained from X-ray diffraction, and the chemical composition of its surface was checked by X-ray photoelectron spectroscopy. The prosperous decorating of LDH on the sheets of rGO and GO was authenticated by the energy dispersive X-ray spectroscopy analysis and micrographs of scanning electron and transmission electron microscopy. The photo-assisted sonocatalytic activity of the prepared nanocomposites was appraised for the decomposition of dimethyl phthalate (DMP) as a plasticizer. The highest decomposition efficiency of 100% was obtained in the existence of CoCr LDH/rGO nanocomposite (0.5 g/L) during 20 min of reaction time via photo-assisted sonocatalysis. The rGO improved the catalytic activity of the CoCr LDH by increasing the specific surface area from 1.2 m²/g to 4.5 m²/g and reducing the band gap from 1.7 eV to 1.3 eV. Moreover, the results of the colony-forming unit method endorsed antibacterial property improvement of the CoCr LDH via hybridizing with rGO. The results of this research provide an optimistic perspective for applying carbonous-based nanocomposites of CoCr LDH as a novel catalyst with antibacterial properties in photo-assisted sonocatalytic processes.

An Electrochemical Screen-Printed Sensor Based on Gold-Nanoparticle-Decorated Reduced Graphene Oxide-Carbon Nanotubes Composites for the Determination of 17-β Estradiol

In this study, a screen-printed electrode (SPE) modified with gold-nanoparticle-decorated reduced graphene oxide-carbon nanotubes (rGO-AuNPs/CNT/SPE) was used for the determination of estradiol (E2). The AuNPs were produced through an eco-friendly method utilising plant extract, eliminating the need for severe chemicals, and remove the requirements of sophisticated fabrication methods and tedious procedures. In addition, rGO-AuNP serves as a dispersant for the CNT to improve the dispersion stability of CNTs. The composite material, rGO-AuNPs/CNT, underwent characterisation through scanning electron microscopy (SEM), ultraviolet-visible absorption spectroscopy (UV-vis), Fourier-transform infrared (FTIR) spectroscopy, and atomic force microscopy (AFM). The electrochemical performance of the modified SPE for estradiol oxidation was characterised using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The rGO-AuNPs/CNT/SPE exhibited a notable improvement compared to bare/SPE and GO-CNT/SPE, as evidenced by the relative peak currents. Additionally, we employed a baseline correction algorithm to accurately adjust the sensor response while eliminating extraneous background components that are typically present in voltammetric experiments. The optimised estradiol sensor offers linear sensitivity from 0.05-1.00 µM, with a detection limit of 3 nM based on three times the standard deviation (3δ). Notably, this sensing approach yields stable, repeatable, and reproducible outcomes. Assessment of drinking water samples indicated an average recovery rate of 97.5% for samples enriched with E2 at concentrations as low as 0.5 µM%, accompanied by only a modest coefficient of variation (%CV) value of 2.7%.

Recent advances in carbon-based materials for high-performance perovskite solar cells: gaps, challenges and fulfillment

Presently, carbon-based nanomaterials have shown tremendous potential for energy conversion applications. Especially, carbon-based materials have emerged as excellent candidates for the fabrication of halide perovskite-based solar cells, which may lead to their commercialization. In the last decade, PSCs have rapidly developed, and these hybrid devices demonstrate a comparable performance to silicon-based solar cells in terms of power conversion efficiency (PCE). However, PSCs lag behind silicon-based solar cells due to their poor stability and durability. Generally, noble metals such gold and silver are employed as back electrode materials during the fabrication of PSCs. However, the use of these expensive rare metals is associated with some issues, urgently necessitating the search for cost-effective materials, which can realize the commercial applications of PSCs due to their interesting properties. Thus, the present review shows how carbon-based materials can become the main candidates for the development of highly efficient and stable PSCs. Carbon-based materials such as carbon black, graphite, graphene nanosheets (2D/3D), carbon nanotubes (CNTs), carbon dots, graphene quantum dots (GQDs) and carbon nanosheets show potential for the laboratory and large-scale fabrication of solar cells and modules. Carbon-based PSCs can achieve efficient and long-term stability for both rigid and flexible substrates because of their high conductivity and excellent hydrophobicity, thus showing good results in comparison to metal electrode-based PSCs. Thus, the present review also demonstrates and discusses the latest state-of-the-art and recent advances for carbon-based PSCs. Furthermore, we present perspectives on the cost-effective synthesis of carbon-based materials for the broader view of the future sustainability of carbon-based PSCs.

Oxidative Cleavage of β-O-4 Linkage in Lignin via Co Nanoparticles Embedded in 3DNG as Catalyst

The cleavage of β-O-4 linkage in lignin is one of the key steps for oxidative conversion of lignin to low-molecular-weight aromatics. Herein, Co nanoparticles embedded in three-dimensional network of nitrogen-doped graphene (Co/NG@3DNG-X) were prepared through an immersion-pyrolysis procedure, in which X denotes the pyrolysis temperature. The detailed characterization of Co/NG@3DNG-X shows that the Co nanoparticles are coated with a few layers of nitrogen-doped graphene (NG) sheets that are further embedded in 3DNG matrix. The catalytic activities of the Co/NG@3DNG-X for the oxidative cleavage of β-O-4 linkage in lignin model compounds with O₂ as oxidant are explored. It is demonstrated that catalytic activities of as-prepared Co/NG@3DNG-X can be tuned by varying the pyrolysis condition, and the Co/NG@3DNG-900 shows the highest catalytic activity, which is attributed to the enriched Co-N_x species, the strong surface basicity, the high specific surface and the mesoporous motif of 3DNG network. More pronouncedly, the Co/NG@3DNG-900 can also effectively catalyze the oxidative cleavage of organosolv lignin, generating certain monomeric aromatics. Additionally, the intrinsic magnetic property of Co nanoparticles makes the Co/NG@3DNG-X be easily recovered from the reaction mixture, and the as-coated thin NG layer can protect Co nanoparticle from oxidation condition, which putting together afford the Co/NG@3DNG-X with good reusability and stability.

Optimization of reduced Graphene oxide synthesis using central composite design analysis-A waste to value approach

In recent times, reduced graphene oxide has gained more attention in various fields. In our study, a direct synthesis of reduced graphene oxide using a novel carbon-rich agro-waste from Pennisetum glaucum was used. Ferrocene acted as an oxidizing agent during thermal degradation at 300 °C for 15 and 20 min to promote graphene oxide and reduced graphene oxide formation. The X-ray diffraction peak at 2θ indicating a shift from 16.86 to 24.28°, presence of functional groups like -OH stretching, -C = C-, C = O, C-O, and C-OH by Fourier transmission infrared spectroscopy, prominent D and G bands at 1308 cm^-1 and 1578 cm^-1 by Raman spectra and UV-visible spectroscopy peak shift from 235 to 245 nm (π-π*, C = C bonds) confirmed the reduction of graphene oxide to reduced graphene oxide. The average particle size values 233.3 nm for graphene oxide and 63.57 nm for reduced graphene oxide illustrate the nanoscale range of our synthesized material. The negative zeta potential values in the range - 45.5 mV and - 29.5 mV for graphene oxide and its reduced forms infer the dispersion stability along with surface oxygen group presence. We have also highlighted the formation of graphene oxide quantum dots by magnetic stirring and confirmed by UV transilluminator and photoluminescence spectra. The photodegradation efficiency was optimized using central composite design for dosage, dye concentration, pH, and time for both malachite green and reactive blue dye. The kinetic studies report pseudo-first-order kinetic model for catalytic degradation and statistical Analysis of variance proved the significance of the process for p value < 0.05. Thus, the synthesized graphene materials could be used as a potential candidate for environmental applications.

Effective Removal of Metal ion and Organic Compounds by Non-Functionalized rGO

Effective removal of heavy metals from water is critical for environmental safety and public health. This work presents a reduced graphene oxide (rGO) obtained simply by using gallic acid and sodium ascorbate, without any high thermal process or complex functionalization, for effective removal of heavy metals. FTIR and Raman analysis show the effective conversion of graphene oxide (GO) into rGO and a large presence of defects in rGO. Nitrogen adsorption isotherms show a specific surface area of 83.5 m2/g. We also measure the zeta-potential of the material showing a value of -52 mV, which is lower compared to the -32 mV of GO. We use our rGO to test adsorption of several ion metals (Ag (I), Cu (II), Fe (II), Mn (II), and Pb(II)), and two organic contaminants, methylene blue and hydroquinone. In general, our rGO shows strong adsorption capacity of metals and methylene blue, with adsorption capacity of qmax = 243.9 mg/g for Pb(II), which is higher than several previous reports on non-functionalized rGO. Our adsorption capacity is still lower compared to functionalized graphene oxide compounds, such as chitosan, but at the expense of more complex synthesis. To prove the effectiveness of our rGO, we show cleaning of waste water from a paper photography processing operation that contains large residual amounts of hydroquinone, sulfites, and AgBr. We achieve 100% contaminants removal for 20% contaminant concentration and 63% removal for 60% contaminant concentration. Our work shows that our simple synthesis of rGO can be a simple and low-cost route to clean residual waters, especially in disadvantaged communities with low economical resources and limited manufacturing infrastructure.

Green synthesis of graphene-based metal nanocomposite for electro and photocatalytic activity; recent advancement and future prospective

The presence of pollutants in waste water is a demanding problem for human health. Investigations have been allocated to study the adsorptive behavior of graphene-based materials to remove pollutants from wastewater. Graphene (GO) due to its hydrophilicity, high surface area, and oxygenated functional groups, is an effective adsorbent for the removal of dyes and heavy metals from water. The disclosure of green synthesis opened the gateway for the economic productive methods. This article reveals the fabrication of graphene-based composite from aloe vera extract using a green method. The proposed mechanism of GO reduction via plant extract has also been mentioned in this work. The mechanism associated with the removal of dyes and heavy metals by graphene-based adsorbents and absorptive capacities of heavy metals has been discussed in detail. The toxicity of heavy metals has also been mentioned here. The Polyaromatic resonating system of GO develops significant π-π interactions with dyes whose base form comprises principally oxygenated functional groups. This review article illustrates a literature survey by classifying graphene-based composite with a global market value from 2010 to 2025 and also depicts a comparative study between green and chemical reduction methods. It presents state of art for the fabrication of GO with novel adsorbents such as metal, polymer, metal oxide and elastomers-based nanocomposites for the removal of pollutants. The current progress in the applications of graphene-based composites in antimicrobial, anticancer, drug delivery, and removal of dyes with photocatalytic efficacy of 73% is explored in this work. It gives a coherent overview of the green synthesis of graphene-based composite, various prospective for the fabrication of graphene, and their biotoxicity.

Eco-Friendly Reduction of Graphene Oxide by Aqueous Extracts for Photocatalysis Applications

In the present work, reduced graphene oxide was obtained by green synthesis, using extracts of Larrea tridentata (gobernadora) and Capsicum Chinense (habanero). Graphene oxide was synthesized by the modified Hummers' method and subsequently reduced using natural extracts to obtain a stable and environmentally friendly graphene precursor. Consequently, the gobernadora aqueous extract was found to have a better reducing power than the habanero aqueous extract. This opportunity for green synthesis allows the application of RGO in photocatalysis for the degradation of the methylene blue dye. Degradation efficiencies of 60% and 90% were obtained with these materials.

Influence of the ultrasound cavitation intensity on reduced graphene oxide functionalization

Graphene is a valuable and useful nanomaterial due to its exceptionally high tensile strength, electrical conductivity and transparency, as well as the ability to tune its materials properties via functionalization. One of the most important features needed to integrate functionalized graphene into products via scalable processing is the effectiveness of graphene dispersion in aqueous and organic solvents. In this study, we aimed to achieve the functionalization of reduced graphene oxide (rGO) by sonication in a one-step process using polyvinyl alcohol (PVA) as a model molecule to be bound to the rGO surface. We investigated the influence of the sonication energy on the efficacy of rGO functionalization. The correlation between the performance of the high-intensity ultrasonic horn and the synthesis of the PVA functionalized rGO was thoroughly investigated by TGA coupled with MS, and IR, Raman, XPS, Laser diffraction, and SEM analysis. The results show that the most soluble PVA-functionalized rGO is achieved at 50% of the ultrasonic horn amplitude. Analysis of cavitation dynamics revealed that in the near vicinity of the horn it is most aggressive at the highest amplitude (60%). This causes rGO flakes to break into smaller domains, which negatively affects the functionalization process. On the other hand, the maximum of the pressure pulsations far away from the horn is reached at 40% amplitude, as the pressure oscillations are attenuated significantly in the 2-phase flow region at higher amplitudes. These observations corelate well with the measured degree of functionalization, where the optimum functionalized rGO dispersion is reached at 50% horn amplitude, and generally imply that cavitation intensity must be carefully adjusted to achieve optimal rGO functionalization.

Construct α-FeOOH-Reduced Graphene Oxide Aerogel as a Carrier for Glucose Oxidase Electrode

A promising α-FeOOH-reduced graphene oxide aerogel (FeOOH-GA) has been prepared for the assembly of an enzyme electrode. The α-FeOOH-reduced graphene oxide aerogel was characterized by X-ray powder diffraction, field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The results reveal that graphene oxide is reduced by Fe²⁺ ion and α-FeOOH nanorods anchored on the reduced graphene oxide sheet through the Fe-O-C bond. Analyses using scanning electron microscopy and the Brunauer–Emmett–Teller method show that FeOOH-GA displays a various and interconnected pore structure. The FeOOH-GA was used as a support material on the glass carbon electrode (GCE) for glucose oxidase (GOD). Electrochemistry properties and bioelectrocatalytic activities of Nafion/GOD/FeOOH-GA/GCE were achieved from cyclic voltammetry and electrochemical impedance spectroscopy. The results show that Nafion/GOD/FeOOH-GA/GCE maintains outstanding catalytic activity and electrochemical properties. The FeOOH-GA could immobilize GOD through the hydrophobicity of the reduced graphene oxide and hydroxide radical of α-FeOOH. Appropriate α-FeOOH and diversified pore structure are beneficial for electron transfer, enzyme electrode storage, and interfacial electron transfer rate. All results indicated that the α-FeOOH-reduced graphene oxide aerogel as a carrier could effectively immobilize the tested enzyme.

Fabrication data of two light-responsive systems to release an antileishmanial drug activated by infrared photothermal heating

The data provided in this study are related to the fabrication of two light-responsive systems based on reduced graphene oxide (rGO) functionalized with the polymers Pluronic P123 (P123), rGO-P123, and polyethyleneimine (PEI), rGO-PEI, and loaded with amphotericin B (AmB), an antileishmanial drug. Here are described the experimental design to obtain the systems and characterization methods, such as Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), Raman Spectroscopy, Powder X-Ray Diffraction, Transmission Electron Microscopy, Scanning Electron Microscopy and Thermogravimetric Analyses. Also, AmB spectroscopy studies are described. The materials rGO-P123 and rGO-PEI were loaded with AmB and the optimization of AmB and polymer fragments structures revealed several possible hydrogen bonds formed between the materials and the drug. The drug release was analyzed with and without Near-Infrared (NIR) light. In the studies conducted under NIR light irradiation for 10 min, an infrared lamp was disposed at 64 cm from the samples and an optical fiber thermometer was employed to measure the temperature variation. Cytotoxicity studies and antiproliferative assays against Leishmania amazonensis promastigotes were evaluated. The complete work data entitled Amphotericin-B-Loaded Polymer-Functionalized Reduced Graphene Oxides for Leishmania amazonensis Chemo-Photothermal Therapy have been published to Colloids and Surfaces B: Bionterfaces (https://doi.org/10.1016/j.colsurfb.2021.112169) [1].

Green Reduction of Graphene Oxide Involving Extracts of Plants from Different Taxonomy Groups

Graphene, a remarkable material, is ideal for numerous applications due to its thin and lightweight design. The synthesis of high-quality graphene in a cost-effective and environmentally friendly manner continues to be a significant challenge. Chemical reduction is considered the most advantageous method for preparing reduced graphene oxide (rGO). However, this process necessitates the use of toxic and harmful substances, which can have a detrimental effect on the environment and human health. Thus, to accomplish the objective, the green synthesis principle has prompted researchers worldwide to develop a simple method for the green reduction of graphene oxide (GO), which is readily accessible, sustainable, economical, renewable, and environmentally friendly. For example, the use of natural materials such as plants is generally considered safe. Furthermore, plants contain reducing and capping agents. The current review focuses on the discovery and application of rGO synthesis using extracts from different plant parts. The review aims to aid current and future researchers in searching for a novel plant extract that acts as a reductant in the green synthesis of rGO, as well as its potential application in a variety of industries.

Macrocycle-Functionalized RGO for Gas Sensors for BTX Detection Using a Double Transduction Mode

To fabricate mass and resistive sensors based on reduced graphene oxide (RGO), we investigated the functionalization of RGO by tetra tert-butyl phthalocyanine (PcH2tBu), which possesses a macroring and tert-butyl peripheral groups. Herein, we present the gas sensor responses of the functionalized RGO toward benzene, toluene, and xylene (BTX) vapors. The RGO was obtained by the reduction of graphene oxide (GO) using citrate as a reducing agent, while the functionalization was achieved non-covalently by simply using ultrasonic and heating treatment. The sensor devices based on both QCM (quartz crystal microbalance) and resistive transducers were used simultaneously to understand the reactivity. Both the GO and the RGO showed less sensitivity to BTX vapors, while the RGO/PcH2tBu presented enhanced sensor responses. These results show that the p-network plays a very important role in targeting BTX vapors. The resistive response analysis allowed us to state that the RGO is a p-type semiconductor and that the interaction is governed by charge transfer, while the QCM response profiles allowed use to determine the differences between the BTX vapors. Among BTX, benzene shows the weakest sensitivity and a reactivity in the higher concentration range (>600 ppm). The toluene and xylene showed linear responses in the range of 100–600 ppm.

Assessment of antioxidant and cytotoxicity activities against A-549 lung cancer cell line by synthesized reduced graphene oxide nanoparticles mediated by Camellia sinensis

Camellia sinensis (green tea leaves) which acts as a reducing agent was used for the reduction of graphene oxide (GO) to obtain reduced graphene oxide (RGO). Anionic surfactant SDS was used to enhance the stability of synthesized reduced graphene oxide nanoparticles. Characterized reduced graphene oxide nanoparticle grain size was calculated to be 3.92 nm from the X-ray diffraction method, whereas zeta potential was measured - 35.23 ± 5.45 mV at room temperature. Antioxidant and cell cytotoxicity against A-549 lung carcinoma cells were also studied. Phytochemical content of Camellia sinensis imparts feasible DPPH activity of 85.98 ± 2.49% against RGO, whereas ABTS scavenging activity was found to be 88.87 ± 1.74% followed by measurement of the total phenolic content of 842 ± 13.33 µg/gm. RGO at concentration 400 µg/ml showed an optimum level of hemolysis at pH 7.4 (4.92 ± 1.20%) than pH 5.6 (11.15 ± 0.03%). Cytotoxicity activity studied by MTT assay of RGO on A-549 lung carcinomas cells was compared with drug doxorubicin. The bandgap energy of RGO was calculated to be 3.97 eV from absorption data, hence reveals the generation of oxidative stress in the A-549 lung cancer cell line. Thus, the surfactant and phytochemicals found in Camellia sinensis enhanced the stability of RGO, thereby providing enough energy to destabilize the target cells without affecting healthy cells, hence suggests its role in therapeutics application.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-03015-z.

Quercetin-rGO based mercury-free electrode for the determination of toxic Cd (II) and Pb (II) ions using DPASV technique

Metal ion pollution poses serious threat to environment. Analysis of Cd (II) and Pb (II) ions using chemically modified mercury free electrode is a feasible routine analytical tool. Developing an electrode surface modified with conductive 2D carbon and metal complexing ligand created a synergetic effect towards sensitive and selective electrochemical determination of metal ions. The present study focused on green chemistry approach towards synthesis of reduced graphene oxide using a natural flavonoid (Quercetin) that acts as a reducing, functionalizing agent and also as metal complexing agent. This quercetin reduced graphene oxide (Q-rGO) was surface modified over paraffin wax impregnated graphite electrode. The resulting Q-rGO electrode was used as a mercury-free electrode for simultaneous analysis of Pb (II) and Cd (II) ions. Physico-chemical parameters of the synthesized Q-rGO and modified electrodes were characterized using X-ray diffraction, UV-Vis, FT-IR, and Raman spectrometer. The morphology of the material and surface topography of the modified electrode was observed using HR-TEM and FESEM, respectively. Cyclic voltammetry (CV) and AC impedance (EIS) were adopted for electrochemical characterization and Differential pulse anodic stripping voltammetry (DPASV) was chosen for simultaneous sensing of metal ions using Q-rGO electrode. Analytical parameters such as effect of electrolyte, effect of pH, preconcentration time and deposition potential were optimized. The experimental results suggested that the Q-rGO electrode is capable of sensing Pb (II) and Cd (II) ions individually and simultaneously. Inference from the calibration plot showed that the Q-rGO electrode was capable of sensing the concentration range of Cd (II) ion form 0.19 to 2.5 μgL^-1 with LOD-0.05 μgL^-1 and Pb (II) ions from 0.19 to 3.1 μgL^-1 with LOD 0.06 μgL^-1.

Biosynthesis of reduced graphene oxide using Turbinaria ornata and its cytotoxic effect on MCF-7 cells

Graphene‐based nanomaterials are gaining importance in biomedicine because of their large surface areas, solubility, and biocompatibility. Green synthesis is the most economical method for application, as it is rapid and sustainable. Biofunctionalized reduced graphene oxide (TrGO) nanosheets were synthesized using methanol extract of Turbinaria ornata, and bioreduction of graphene oxide was primarily confirmed and characterized using UV‐visible, Fourier transform infrared (FTIR), and X‐ray diffraction spectroscopy and further characterized by zeta potential and transmission electron microscopy. The FTIR spectra of TrGO showed a decrease in the band intensities of oxygen groups, thus confirming effective deoxygenation. The zeta potential value of −34.6 mV revealed that synthesized TrGO was highly stable. The cytotoxic effect of TrGO against MCF‐10A and MCF‐7 cells was ascertained using MTT assay, showed a greater cytotoxic effect on MCF‐7 cells. The IC₅₀ of TrGO treatment against MCF‐7 was calculated to be 31.25 µg, which is onefold lower than the cytotoxic effect of methanolic extract of T. ornata (60.0 ± 1.14 µg/ml). In addition, there was a statistically significant difference in cell viability between MCF‐10A and MCF‐7 cells in the treatment of TrGO. Hence, this study results in an efficient green reductant for producing rGO nanosheets that possess cytotoxicity against breast cancer cells.

Features and Consequences of Isopropanol Burning off PTFE-rGO Aerogels

An improved procedure for the preparation of aerogel granules of polytetrafluoroethylene-graphene oxide (PTFE-GO) with a composition of 50:50 (in wt %) and a specific density of 35 ± 2 mg/cm³ is described. The technique practically excludes the granule cracking. The specific density of the pellets after reduction using hydrazine vapor and annealing at 370 °C decreased to 29 ± 2 mg/cm³. The PTFE-reduced GO (rGO) pellets obtained were tested as a recyclable sorbent for isopropyl alcohol (IPA) in sorption/combustion cycles. It has been shown that the aerogel sorption capacity for IPA increases from 35.6 to 39.3 g/g as a result of alcohol burning off. During the combustion of IPA, the temperature of an individual pellet can exceed 300 °C. When several contingent pellets are burned, the temperature of their heating increases. The fine-pored structure of the near-surface layer of the granule is destroyed during the alcohol burning, the internal structure with larger pores is exposed, and the relative proportion of PTFE on the surface of the granules decreases. It was also shown that the specific surface area of PTFE-rGO increases from 26 to 49 m²/g during cycling.

Highly Water-Dispersible Graphene Nanosheets From Electrochemical Exfoliation of Graphite

The electrochemical exfoliation of graphite has been considered to be an effective approach for the mass production of high-quality graphene due to its easy, simple, and eco-friendly synthetic features. However, water dispersion of graphene produced in the electrochemical exfoliation method has also been a challenging issue because of the hydrophobic properties of the resulting graphene. In this study, we report the electrochemical exfoliation method of producing water-dispersible graphene that importantly contains the relatively low oxygen content of <10% without any assistant dispersing agents. Through the mild in situ sulfate functionalization of graphite under alkaline electrochemical conditions using a pH buffer, the highly water-dispersible graphene could be produced without any additional separation processes of sedimentation and/or centrifugation. We found the resulting graphene sheets to have high crystalline basal planes, lateral sizes of several μm, and a thickness of <5 nm. Furthermore, the high aqueous dispersion stability of as-prepared graphene could be demonstrated using a multi-light scattering technique, showing very little change in the optical transmittance and the terbiscan stability index over time.

Iron molybdenum selenide supported on reduced graphene oxide as an efficient hydrogen electrocatalyst in acidic and alkaline media

It is of great significance to develop inexpensive and high-efficiency electrocatalysts for the hydrogen evolution reaction (HER). In this work, we synthesized iron molybdenum selenide (FeSe₂-MoSe₂) loaded on reduced graphene oxide (FeSe₂-MoSe₂/rGO) by a one-step hydrothermal method. We further optimized the Fe/Mo ratio and determined the best ratio to be 1-1. In acidic (or alkaline) solution, the optimized FeSe₂-MoSe₂(1-1)/rGO has a small Tafel slope of 55 (or 80) mV dec^-1 and needs an overpotential of 101 (or 178) mV to achieve 10 mA cm^-2. These good properties are mainly due to the structure of bimetallic selenides combining rGO. Moreover, rGO enhances the electrical conductivity. Furthermore, the synergistic effect between FeSe₂-MoSe₂(1-1) and rGO results in better HER performance. Density functional theory (DFT) calculation proves that FeSe₂-MoSe₂(1-1)/rGO has a small work function. Based on our reasonable design and analysis, FeSe₂-MoSe₂(1-1)/rGO is expected to be an efficient and robust catalyst for large-scale applications.

Conductive In Situ Reduced Graphene Oxide-Silk Fibroin Bionanocomposites

This research paper describes the fabrication of bionanocomposites (BNCs) based on silk fibroin (SF) and reduced graphene oxide (rGO). The recorded UV-visible (UV-vis) spectra of the sample confirm the reduction of GO to rGO in SF by showing a plasmon resonance band within the wavelength range of 261-268 nm. The X-ray diffraction (XRD) peak at 11.6° corresponding to the GO intensity decreases with increasing reaction time, resulting in rGO in the SF host matrix. The morphological behavior of the SF-rGO BNCs is scrutinized using scanning electron microscopy (SEM), and the images clearly indicate the existence of rGO within the matrix. The increasing amount of GO in the SF shows broken graphene sheets, which can increase the surface roughness and establish a strong physical contact between the SF and rGO nanosheets. The high-resolution transmission electron microscope (HR-TEM) image of the bionanocomposite showed that the formed rGO encompassments of fewer layers are stacked, each with fewer wrinkles and folding. The Raman spectroscopy confirmed the formation of rGO by showing the increased intensity ratio of D to G band (I D/I G) in the bionanocomposite samples. The rGO effect on the electrical conductivity is measured, and the results show that DC conductivity increases from 1.28 × 10-9 to 82.4 × 10-9 S/cm with an increase in the GO content in the SF biopolymer. The investigations demonstrate loss of the insulation property and improved conducting behavior of the SF biopolymer.

Variable-Angle Spectroscopic Ellipsometry of Graphene-Based Films

A review of the authors’ research works on Variable-Angle Spectroscopy (VASE) of graphene-based films is presented. The interaction of graphene oxide (GO) with magnetron-sputtered metals is a promising research area. VASE optical models of GO thin films deposited on magnetron-sputtered titanium (Ti), silver (Ag) and gold (Au) are discussed. Moreover, the optical properties of graphene nanoplatelet (GNPS) films and reduced graphene oxide (RGO) stabilized with Poly(Sodium 4-Styrenesulfonate) (PSS) films, which are less studied graphene-related materials, are shown. Finally, different optical behaviors of chemical vapor deposition (CVD)-grown monolayer, bilayer, and trilayer graphene films on silicon and polyethylene terephthalate (PET) substrates are recapitulated.

Au101-rGO nanocomposite: immobilization of phosphine-protected gold nanoclusters on reduced graphene oxide without aggregation

Graphene supported transition metal clusters are of great interest for potential applications, such as catalysis, due to their unique properties. In this work, a simple approach to deposit Au₁₀₁(PPh₃)₂₁Cl₅ (Au₁₀₁NC) on reduced graphene oxide (rGO) via an ex situ method is presented. Reduction of graphene oxide at native pH (pH ≈ 2) to rGO was performed under aqueous hydrothermal conditions. Decoration of rGO sheets with controlled content of 5 wt% Au was accomplished using only pre-synthesised Au₁₀₁NC and rGO as precursors and methanol as solvent. High resolution scanning transmission electron microscopy indicated that the cluster size did not change upon deposition with an average diameter of 1.4 ± 0.4 nm. It was determined that the rGO reduction method was crucial to avoid agglomeration, with rGO reduced at pH ≈ 11 resulting in agglomeration. X-ray photoelectron spectroscopy was used to confirm the deposition of Au₁₀₁NCs and show the presence of triphenyl phosphine ligands, which together with attenuated total reflectance Fourier transform infrared spectroscopy, advocates that the deposition of Au₁₀₁NCs onto the surface of rGO was facilitated via non-covalent interactions with the phenyl groups of the ligands. Inductively coupled plasma mass spectrometry and thermogravimetric analysis were used to determine the gold loading and both agree with a gold loading of ca. 4.8-5 wt%. The presented simple and mild strategy demonstrates that good compatibility between size-specific phosphine protected gold clusters and rGO can prevent aggregation of the metal clusters. This work contributes towards producing an agglomeration-free synthesis of size-specific ligated gold clusters on rGO that could have wide range of applications.

Functionalized Reduced Graphene Oxide Thin Films for Ultrahigh CO2 Gas Sensing Performance at Room Temperature

The demand for carbon dioxide (CO₂) gas detection is increasing nowadays. However, its fast detection at room temperature (RT) is a major challenge. Graphene is found to be the most promising sensing material for RT detection, owing to its high surface area and electrical conductivity. In this work, we report a highly edge functionalized chemically synthesized reduced graphene oxide (rGO) thin films to achieve fast sensing response for CO₂ gas at room temperature. The high amount of edge functional groups is prominent for the sorption of CO₂ molecules. Initially, rGO is synthesized by reduction of GO using ascorbic acid (AA) as a reducing agent. Three different concentrations of rGO are prepared using three AA concentrations (25, 50, and 100 mg) to optimize the material properties such as functional groups and conductivity. Thin films of three different AA reduced rGO suspensions (AArGO25, AArGO50, AArGO100) are developed and later analyzed using standard FTIR, XRD, Raman, XPS, TEM, SEM, and four-point probe measurement techniques. We find that the highest edge functionality is achieved by the AArGO25 sample with a conductivity of ~1389 S/cm. The functionalized AArGO25 gas sensor shows recordable high sensing properties (response and recovery time) with good repeatability for CO₂ at room temperature at 500 ppm and 50 ppm. Short response and recovery time of ~26 s and ~10 s, respectively, are achieved for 500 ppm CO₂ gas with the sensitivity of ~50 Hz/µg. We believe that a highly functionalized AArGO CO₂ gas sensor could be applicable for enhanced oil recovery, industrial and domestic safety applications.

Plasma Assisted Reduction of Graphene Oxide Films

The past decade has seen enormous efforts in the investigation and development of reduced graphene oxide (GO) and its applications. Reduced graphene oxide (rGO) derived from GO is known to have relatively inferior electronic characteristics when compared to pristine graphene. Yet, it has its significance attributed to high-yield production from inexpensive graphite, ease of fabrication with solution processing, and thus a high potential for large-scale applications and commercialization. Amongst several available approaches for GO reduction, the mature use of plasma technologies is noteworthy. Plasma technologies credited with unique merits are well established in the field of nanotechnology and find applications across several fields. The use of plasma techniques for GO development could speed up the pathway to commercialization. In this report, we review the state-of-the-art status of plasma techniques used for the reduction of GO-films. The strength of various techniques is highlighted with a summary of the main findings in the literature. An analysis is included through the prism of chemistry and plasma physics.

Conducting materials as building blocks for electronic textiles

ABSTRACT

To realize the full gamut of functions that are envisaged for electronic textiles (e-textiles) a range of semiconducting, conducting and electrochemically active materials are needed. This article will discuss how metals, conducting polymers, carbon nanotubes, and two-dimensional (2D) materials, including graphene and MXenes, can be used in concert to create e-textile materials, from fibers and yarns to patterned fabrics. Many of the most promising architectures utilize several classes of materials (e.g., elastic fibers composed of a conducting material and a stretchable polymer, or textile devices constructed with conducting polymers or 2D materials and metal electrodes). While an increasing number of materials and devices display a promising degree of wash and wear resistance, sustainability aspects of e-textiles will require greater attention.

Dielectric Polarization and Electrorheological Response of Poly(ethylaniline)-Coated Reduced Graphene Oxide Nanoflakes with Different Reduction Degrees

We prepared poly(ethylaniline)-coated graphene oxide nanoflakes and then treated them with different concentrations of hydrazine solution to form dielectric composite nanoflakes having different reduction degrees of reduced graphene oxide core and insulating polyethylaniline shell (PEANI/rGO). The morphology of PEANI/rGO was observed by scanning electron microscopy, while the chemical structure was confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectrometer. The influence of reduction degrees on the conductivity, dielectric polarization and electrorheological effect of PEANI/rGO in suspensions was investigated by dielectric spectroscopy and rheological test under electric fields. It shows that the PEANI/rGO has two interfacial polarization processes respectively due to rGO core and PEANI shell. As the number of hydrazine increases, the conductivity and polarization rate of rGO core increase. As a result, the difference between the polarization rate of rGO core and that of the PEANI shell gradually becomes large. This increased difference does not significantly decrease the yield stress but causes the flow instability of PEANI/GO suspensions under the simultaneous action of electric and shear fields.

Ciprofloxacin and Graphene Oxide Combination-New Face of a Known Drug

Drug modification with nanomaterials is a new trend in pharmaceutical studies and shows promising results, especially considering carbon-based solutions. Graphene and its derivatives have attracted much research interest for their potential applications in biomedical areas as drug modifiers. The following work is a comprehensive study regarding the toxicity of ciprofloxacin (CIP) modified by graphene oxide (GO). The influence on the morphology, viability, cell death pathway and proliferation of T24 and 786-0 cells was studied. The results show that ciprofloxacin modified with graphene oxide (CGO) shows the highest increase in cytotoxic potential, especially in the case of T24 cells. We discovered a clear connection between CIP modification with GO and the increase in its apoptotic potential. Our results show that drug modification with carbon-based nanomaterials might be a promising strategy to improve the qualities of existing drugs. Nevertheless, it is important to remember that cytotoxicity effects are highly dependent on dose and nanomaterial size. It is necessary to conduct further research to determine the optimal dose of GO for drug modification.

New fabrication method for producing reduced graphene oxide flexible electrodes by using a low-power visible laser diode engraving system

The fabrication of bendable electronic devices is a scientific-technological area of very rapid advance in which new materials and fabrication techniques are being continuously developed. In these kinds of devices, the fabrication of flexible conductive electrodes adherent to the substrate is a key factor. Further, eco-friendliness, low cost and fast production are essential requirements for the successful progress of new technologies. In this work, a novel method for obtaining graphene-based flexible electrodes is presented. Conductive films were obtained by means of the visible laser irradiation of graphene oxide layers deposited on polyethylene terephthalate substrates and self-standing membranes sandwiched between glass slides. Despite the low power of the laser system, the numerical simulations indicate the development of temperatures over 1000 K throughout the irradiated material. The laser-induced spatially confined heating leads to the reduction of the graphene oxide material, whereas the glass-based sandwich assembly avoids reoxidation from the surrounding air. By scanning and pixelated modes, reduced graphene oxide electrodes, up to 100 μm in thickness, and with a resistivity as low as 6 × 10^-4 Ωm, were obtained in an easy and versatile way. Proof-of-concept microsupercapacitors and electrochemical sensors were fabricated with this technique, showing promising performance.

Synthesis and characterization of reduced graphene oxide using the aqueous extract of Eclipta prostrata

In this study, biological deoxygenation of graphene oxide (GO) using an Eclipta prostrata phytoextract was performed via the infusion method. The presence of oxide groups on the surface of graphene and removal of oxides groups by reduction were characterized through morphological and structural analyses. Field emission scanning electron microscopy images revealed that the synthesized GO and rGO were smooth and morphologically sound. Transmission electron microscopy images showed rGO developing lattice fringes with smooth edges and transparent sheets. Atomic force microscopy images showed an increase in the surface roughness of graphite oxide (14.29 nm) compared with that of graphite (1.784 nm) due to the presence of oxide groups after oxidation, and the restoration of surface roughness to 2.051 nm upon reduction. Energy dispersive X-ray analysis indicated a difference in the carbon/oxygen ratio between GO (1.90) and rGO (2.70). Fourier-transform infrared spectroscopy spectrum revealed peak stretches at 1029, 1388, 1578, and 1630 cm^-1 for GO, and a decrease in the peak intensity after reduction that confirmed the removal of oxide groups. X-ray photoelectron microscopy also showed a decrease in the intensity of oxygen peak after reduction. In addition, thermogravimetric analysis suggested that rGO was less thermally stable than graphite, graphite oxide, and GO, with rGO decomposing after heating at temperatures ranging from room temperature to 600 °C.