Thermal Reduction Of Graphene Oxide Research Articles

A SYSTEMATIC INVESTIGATION OF THE STRUCTURAL CHANGES IN CHEMICALLY AND THERMALLY REDUCED GRAPHENE OXIDE USING RAMAN AND XRD

This investigation aimed to explore the characteristics of reduced graphene oxide (rGO) through a comprehensive approach. The synthesis of graphene oxide (GO) began with a customized adaptation of the modified Hummer’s method, followed by subsequent chemical and thermal reduction processes. Chemical reduction involved the use of ascorbic acid, hydrazine hydrate, and sodium borohydride, while thermal reduction occurred at various temperatures in the presence of hydrogen. The study employed a diverse array of analytical techniques to unravel the structural and chemical intricacies of the material. X-ray diffraction (XRD) revealed significant changes indicative of structural transformations. Raman spectroscopy meticulously examined defects and layer formations. Scanning Electron Microscopy (SEM) visualized the evolutionary aspects of the material’s structure. UV–VIS spectroscopy is employed to analyze the optical bandgap of the sample, and the primary importance of this study lies in its application potential for solar cells.

Atomic-Level Insights into Defect-Driven Nitrogen Doping of Reduced Graphene Oxide

Nitrogen-doped graphene has been increasingly utilized in a variety of energy-related applications, serving as a catalyst or support material for fuel cells, and as an anode material for lithium-ion batteries, among others. The thermal reduction of graphene oxide (GO) in nitrogenous sources to incorporate nitrogen, producing nitrogen-doped reduced graphene oxide (NRGO), is the most favored method. Controlling atomic configurations of nitrogen-doped sites is the key factor for tailoring the physico-chemical properties of NRGO, but major challenges remain in identifying detailed atomic arrangements at nitrogen binding sites on highly defective and chemically functionalized GO surfaces. In this paper, we present atomistic-scale modeling of the nitrogen doping process of GO with different types of vacancy defects. Molecular dynamics simulations using a reactive force field indicate that the edge carbon atoms on defect sites are the dominant initiation location for nitrogen doping. Further, first-principles calculations using density functional theory present energetically favorable chemical transition pathways for nitrogen doping. The significance of this work lies in providing important chemical insights for the effective control of the desired properties of NRGO by suggesting a detailed mechanism of the nitrogen doping process of GO.

A comparative study on coconut shell-derived graphene oxide and reduced graphene oxide

Coconut shell (CS) is a waste material with high carbon source potential and is suitable for producing advanced nanomaterials like graphene oxide (GO) and reduced graphene oxide (rGO). However, CS-derived subpar GO and rGO and the lack of comparative studies have restrained their best utilization. This study presents a novel synthesis of high-quality and non-toxic GO and rGO using CS as the precursor, comparing their structural and chemical properties. The synthesis processes involve CS carbonization into graphite, oxidation of graphite into GO using Hummers' method with specific modifications, and non-toxic thermal reduction of GO into rGO. Characterization techniques, including X-ray diffraction, Raman spectroscopy, FTIR, Scanning electron microscopy, and Transmission electron microscopy, confirm successful oxidation and reduction of the samples. Results reveal a well-defined graphitic structure in CS-derived graphite. GO contains oxygen-based functional groups, removed or reduced during thermal reduction. While rGO has fewer defects and restored graphitic arrangement. This study concludes that CS-derived GO and rGO possess desirable properties comparable to those synthesized from pristine graphite, respectively. The results suggest that non-toxic, few-layered, and high-quality GO and rGO synthesized from CS suit biomedical applications, particularly in bone tissue engineering.

Electrophoretic deposition for the interfacial enhancement of BF/PPENK composite: GO vs. Ti3C2Tx MXene

Electrophoretic deposition (EDP) is a novel and promising technique for surface modification, however, the adsorption of Ti3C2Tx MXene or graphene oxide (GO) onto the basalt fiber (BF) surface by EPD and its effects on the mechanical performance of basalt fiber reinforced high-performance thermoplastic (BFRHPTP) composite have yet to be investigated. Here, the mechanical and interfacial properties of the modified BF/PPENK were explored. The influence of the brittle/tough nanostructures in interphase on the mechanical performance of BF reinforced poly(phthalazinone ether nitrile ketone) (BF/PPENK) was elucidated. The results indicated that the thermal reduction of GO contributed even more to enhancing the tensile, flexural, interlaminar shear, and interfacial shear strength of BF/PPENK compared to the heat oxidation of MXene. Particularly, these properties of BF-NH2@GO3/PPENK were improved by approximately 84%, 43%, 60%, and 118% in comparison to BF-Desized/PPENK. This work may provide some guidance on the interfacial modification of the BFRHPTP composites.

Low-temperature compositing of graphene to nanodiamonds by thermal reduction of graphene oxide and photocatalytic properties

Graphene has become a research hotspot in the field of composites due to its special structure and excellent properties The common preparation methods of graphene matrix composites include solvent (hydrothermal) method, sol-gel method, chemical reduction method, electrochemical deposition method, etc. Nanodiamond/reduced graphite oxide (rGO) composites are directly synthesized by low-temperature heat treatment with nanodiamonds and graphite oxide (GO) powders as raw materials with the aid of GO thermal reduction at 195 °C. The degradation ability of samples to methylene blue (MB) under simulated sunlight was tested. Results indicated that GO was thermally reduced to graphene at low temperature, and rGO well combined with diamond. After the introduction of GO, the lattice of nanodiamond underwent distortion. Diamond and graphene formed a quasi-core–shell structure, and the interface between them was well bonded. The composite had a large specific surface area (Brunauer–Emmett–Teller value of 93.13 m2/g). The addition of GO enhanced the absorbance of the samples and reduced the bandgap of nanodiamond. When the ratio of nanodiamond to GO was 6:1, the sample exhibited excellent sunlight photocatalytic activity, and MB degradation rate reached 99.8 % within 40 min. The reduction reaction of GO at low temperature promoted its rapid combination with nanodiamonds. This method had the outstanding advantages of simple process, environment friendliness, and easy mass production.

Short notes: Measurements on the heat capacity of thermal reduced graphene oxide down to 0.3 K

The specific heat of thermally reduced graphene oxide (trGO) was measured by a thermal relaxation method in the temperature range from 0.3 to 275 K. It was found that the temperature dependence of the heat capacity С(Т)/T vs T2 of trGO is nonmonotonic. It has been established that in the temperature range of 0.3–6 K there is an anomalous behavior of the temperature dependence of the heat capacity trGO, sharply changing its character. It is assumed that this anomaly is due to the influence of impurities and defects, structural features.

A facile strategy for improving the hydrophobicity and photo-thermal conversion capability of biochar and its application in the absorption of hazardous chemicals and viscous oil

Biochar is considered as a promising adsorbent due to its unique porous structure, large surface area and lightweight nature. In this study, pomelo peel was used as raw material, and graphene oxide was introduced as a functional material. High-temperature carbonization was employed to achieve simultaneous carbonization of pomelo peel and thermal reduction of graphene oxide, resulting in the preparation of a porous sponge-like biochar with high hydrophobicity, thermal stability and photothermal conversion capability. This biochar was successfully applied to the efficient separation of various oil–water mixtures, demonstrating excellent cyclic adsorption stability. Furthermore, by harnessing its photothermal conversion effect, efficient absorption of viscous oil product was achieved. This study proposes a facile biochar preparation strategy that can expand its application in the field of oil spill emergency treatment and promote the utilization of agricultural waste.

Large-scale Production of Few-Layer Reduced Graphene Oxide by the Rapid Thermal Reduction of Graphene Oxide and Its Structural Characterization

Graphene, a carbon allotrope, is a two-dimensional honeycomb of carbon atoms. Although graphene is a thin material, it is the strongest material known on Earth thanks to the strong carbon bonds in its structure. It is stated that the strength of these carbon bonds in graphene is about 100 times stronger than steel. In this study, graphite was first converted into graphene oxide (GO) by the Improved Hummers method, which is one of the methods suitable for large-scale production. Reduced graphene oxide (RGO) was obtained from the synthesized GOs by thermal reduction. TGA, FTIR, XRD, XPS, Raman, BET, and SEM analyses were used to characterize GO produced using the improved Hummers method and RGO reduced by thermal methods. TGA measurements show that RGO produced using the thermal approach had a lower mass loss than graphite oxidized using the improved Hummers process. This shows that the GO sample prepared using the improved Hummers approach contains a considerable number of distinct oxygen-containing groups. The novelty of the modified Hummers' method lies in its enhanced efficiency in producing graphene oxide through reduced thermal reaction times and improved scalability compared to the original approach in the literature. The C:O ratio of the GO and RGO samples was determined by XPS to be 1.88 and 11.17, respectively. The ID/IG ratio obtained by Raman analysis was 0.973. In addition, RGO's BET surface area was discovered to be 543.6 m2 g-1. These findings demonstrated that graphite was successfully oxidized by an improved Hummers method, and the resulting GO was thermally converted to few-layer RGO.

Simultaneous preparation of ZnO/rGO composites through Zn(OH)2 decomposition and graphite oxide reduction and their photocatalytic properties.

ZnO/reduced graphite oxide (rGO) composites were simultaneously prepared by the thermal reduction of graphite oxide (GO) and the decomposition of Zn(OH)2. The samples were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, photoluminescence, and DRS. Results indicate that Zn(OH)2 was heated and decomposed into ZnO at a low temperature (200 ℃), while GO was reduced to graphene. The synthesized ZnO particles were small and loaded on graphene layers. The ZnO/rGO photocatalysts exhibited excellent photocatalytic activity against methylene blue (MB) under simulated sunlight irradiation. The ZnO/50% rGO photocatalyst showed the best MB photodegradation rate of up to 99.7% within 3min. Synchronous reaction provided an efficient, simple, and fast preparation method for ZnO/rGO composites, with an excellent solar photocatalytic degradation ability.

Enhanced electromagnetic interference shielding using Nanosilver-Decorated Graphene/Poly(vinyl chloride) nanocomposite films

Silver nanoparticles (AgNPs) were prepared by chemical reduction and grafted onto thermally reduced graphene oxide (TRGO) sheets. PVC-based nanocomposite films with various Ag/TRGO concentrations were synthesized via solution casting. The film containing 50 wt% Ag/TRGO exhibited the highest AC conductivity (6.23 × 102 S/cm−1) and DC-conductivity (1.78 × 102 S/cm). In the near-infrared region, films with high Ag/TRGO content showed less than 0.1 % transmission. Film with a thickness of approximately 95 μm demonstrated a shielding effectiveness (SE) of over 100 dB within the frequency range of 100 Hz to 5 MHz. This study highlights the potential of Ag/TRGO nanocomposite films in electromagnetic interference shielding applications.

Antibacterial and antioxidant activities of graphene and graphene oxide synthesis coated silver nanoparticules

Graphene oxide and reduced graphene oxide were rapidly and directly prepared by a thermal shock for a few seconds. After simply subjecting a mixture of intercalated graphite to a temperature of 650 and 850 °C, we obtained a large quantity of tGO and trGO, respectively. Silver nanoparticles were synthesized on the thermal graphene oxide tGO (and thermal reduced graphene oxide trGO) surface. We investigated the obtained tGO, trGO, tGO-Ag, and trGO-Ag nanocomposites using X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, Scanning Electron Microscopy, particle size analysis and RAMAN spectroscopy. The results approved the successful synthesis and functionalizing of silver-graphene nanocomposites. Hence, the exceptional thermal stability was estimated to be 920 °C for tGO (and trGO) from TGA and increased for tGO-Ag (and trGO-Ag). Our study of the antimicrobial and antioxidant activity, as an application for these nanocomposites, revealed a highly effective performance, with demonstrated antibacterial activity against six tested bacterial strains. Additionally, we observed a strong antioxidant capacity that exceeded that of ascorbic acid for the trGO-Ag nanocomposite.

Investigating the impact of nitrogen-doping on the characteristics and performance of reduced graphene oxide for lithium-ion batteries anode through experimental and theoretical study

Recently, graphene-based materials have gained widespread attention due to their remarkable electronic characteristics, which make them ideal for use in a broad range of energy storage applications such as lithium-ion battery (LIB). Despite the potential benefits of graphene-based materials, the process of creating them in a cost-efficient manner remains difficult. Herein, we developed nitrogen-doped reduced graphene oxide (NRGO) through a one-step thermal reduction of graphene oxide (GO) and urea. We evaluated the structure and morphology of NRGO by using scanning electron microscopy (SEM), ultraviolet-visible light (UV–vis) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy, which revealed a wrinkled, layered structure with 8.4 % nitrogen content. Moreover, we also compared the performance of RGO and NRGO as an anode for LIB through various electrochemical characterizations, i.e., cyclic voltammetry (CV), galvanostatic charge discharge (CD), and electrochemical impedance spectroscopy (EIS). The result indicates that NRGO provides 2.6 faster lithium diffusion compared to RGO. To gain insights into lithium migration pathways, density functional theory based nudged elastic band (DFT-NEB) simulations were performed. The results revealed the energy barrier of lithium migration in graphitic-NRGO is estimated to be 0.15 eV, and for its reverse reaction, a barrier of 0.22 eV is required. In conclusion, the NRGO synthesized through this relatively simple process displays a promising prospect for anode component in LIB and the reaction pathway simulation provides an important insight into the understanding of lithium migration on the NRGO surface and its optimization for LIB applications.

Improving thermal conductivity of graphene films with assistance of melamine

Due to the high degree of integration and high-power-density, excessive heat accumulation significantly endangers the performance of electronics. Therefore, developing high-performance thermal interface materials has become particularly vital for ensuring the regular operation of the electronics. Graphene-based materials attract great attention due to graphene’s intrinsic excellent thermal conductivity. However, the internal defects in graphene and the lack of interlayer heat conduction pathways between graphene microsheets dramatically reduce the thermal conductivity of graphene-based materials. Herein, melamine is used to improve the thermal properties of graphene films prepared by thermal reduction of graphene oxide (GO) microsheets. With an addition of 3 wt% of melamine, the in-plane and through-plane thermal conductivities of the graphene films with a thickness of 35 μm reach 1.32 × 103 and 5.09 W m−1 K−1, respectively. This is likely due to the covalent connection of graphene microsheets through amide structure formed by the chemical reaction between melamine and GOs, and the remedy of defects in graphene by nitrogen doping with the assistance of high-temperature annealing. The operation temperature of LED is greatly reduced, when the prepared graphene films is used as thermal interface material, compared to other commercial products. The results provide a promising way to improve the thermal properties of graphene films, which is of great significance for various applications, such as thermal management for high-power-density electronics.

Electrical Conductivity and Antibacterial Activity of Woven Fabrics through Quercetin-Assisted Thermal Reduction of a Graphene Oxide Coating.

Cotton and poly(ethylene terephthalate) (PET) woven fabrics were coated with graphene oxide (GO) using a padding method and the GO deposited on the fiber surfaces was thermally reduced to impart electrical conductivity to the fabrics. To assist the thermal reduction of GO, quercetin (Q)-a natural flavonoid-was used. To this end, before the reduction, the GO-padded fabrics were immersed in Q solutions in ethanol with different Q concentrations. Q enhanced the thermal reduction of GO. Depending on the Q concentration in the solutions, electrical surface resistivities of the cotton fabric of 750 kΩ/sq to 3.3 MΩ/sq and of the PET fabric of 240 kΩ/sq to 730 kΩ/sq were achieved. The cotton and PET fabrics also became hydrophobic, with water contact angles of 163° and 147°, respectively. In addition to the electrical conductivity, the presence of Q resulted in antibacterial activity of the fabrics against Escherichia coli and Staphylococcus aureus.

Layered GeSe/thermally-reduced graphene oxide composites as efficient anodes for high-performance Li-ion batteries

Due to their layered structure and greater electrical conductivity compared to traditional metal oxides, layered metal selenides have been extensively explored as promising electrode materials for Li-ion batteries. The greatest obstacles to their continued growth, however, are the substantial volume change and particle agglomeration during cycling. In this work, layered GeSe/ thermally-reduced graphene oxide (TRG) composites were successfully synthesized by using a facile shear-force exfoliation approach. When a highly conductive TRG matrix was incorporated with GeSe particles, the resultant GeSe/TRG composite electrode achieved an impressive reversible capacity (>840.1 mAh g−1 at 0.1C), improved rate capability as well as excellent cycling stability. The remarkable improvement in electrochemical performance of the GeSe/TRG composite electrode corresponds to the TRG matrix, which potentially constructs an efficient conductive channel and serves as a flexible mechanical buffer for the restriction of volume expansion and particle aggregation.

Sustainable nanohybrid of CaO with rGO for efficient photocatalytic removal of wastewater pollutants

The prominent water pollutants, Safranin (SF) and Eriochrome Black T (EBT) dye extensively used in plastic, leather, complexometric titrations, and textile industries, cause severe toxic impacts on the environment and human health. So, for their elimination, a cost-effective and sustainable hybrid of calcium oxide with reduced graphene oxide (rGO@CaO) was employed, synthesized using waste egg shells (precursor of calcium oxide), and thermal reduction of graphene oxide produced via modified Hummer's method. The sharp PXRD peaks confirmed the crystalline nature of the nanocomposite's pure and deformed spherical nanoparticles (20–40 nm). The removal of dyes was subsequently studied using the rGO@CaO nanocomposite (5–25 mg) at specific reaction conditions investigated (pollutant: 10–50 mgL-1, pH: 3–11, dark–sunlight). Under UV irradiation, the rGO@CaO nanocomposite demonstrated maximal degradation (SF: 97 % and EBT: 93 %) with 10 mg of catalytic dose at the initial dye concentration (10 mgL-1). The efficient photocatalytic efficacy of the rGO@CaO nanocomposite was supported by its small size, large surface area (48.06 m2g−1), higher negative zeta potential (-31.5 mV), and smaller bandgap (2.0 eV). Scavenger analysis revealed that holes, O2, and OH radicals play a crucial role in breaking the complex structure of SF and EBT. After degradation, safer metabolites developed, which was verified by LC-MS analysis. In conclusion, hybrid rGO@CaO nanocomposite is an efficient catalyst for industrial applications with broad potential due to its stability, higher charge separation, cost-effectiveness, and increased reusability (n = 8).

Appealing optoelectronic properties of p-type Cu-G transparent conductor prepared by Cu sputtering and thermal reduction of graphene oxide

Appealing optoelectronic properties of p-type Cu-G transparent conductor prepared by Cu sputtering and thermal reduction of graphene oxide

Significant promotion of the anti-corrosive performance of epoxy zinc-containing coating via in situ reduction of graphene oxide and simultaneous graft it with polyamide curing agent

Two different reduced graphene oxide, i.e. the chemical reduced GO grafted with the polyamide (PGO) and common thermal reduced graphene oxide (RGO), had been used to modify epoxy/Zn composite coatings and their anticorrosive behavior was studied and compared. PGO was innovatively incorporated into the epoxy composite coating during preparing the paint via the solve-thermal treatment of GO in polyamide-651 at 90 °C. Various analyses revealed that GO was reduced in situ and simultaneously grafted with polyamide macromolecules during the solve-thermal treatment. Compared to pristine GO and RGO, PGO displayed improved dispersibility in the resin diluent and its superior effect on improving the anti-corrosive performance of epoxy/Zn coating was confirmed by different corrosion test and surface analysis technique. Moreover, its optimum content in the composite paint was only 0.3 wt%. The excellent anti-corrosion performance of the composite coating could be attributed to the great barrier properties of PGO in the epoxy coating, as well as its good dispersion and compatibility to epoxy matrix.

A Flexible and Wearable Chemiresistive Biosensor Fabricated by Laser Inducing for Real‐Time Glucose Analysis of Sweat

AbstractIn this study, a flexible and wearable chemiresistive biosensor (FWCB) is developed for the real‐time analysis of glucose in sweat on the human skin surface based on a novel detection strategy of p‐type reduced graphene oxide (rGO) sensing film, which met the requirements of rapid, nondestructive testing. The proposed FWCB is fabricated in the form of interdigital electrodes (IEs) made of laser‐induced graphene (LIG) synthesized by the laser inducing of a polyimide (PI) film. Additionally, a semiconducting rGO sensing film modified on the surface of IEs is synthesized by thermal reduction of graphene oxide (GO), which is functionalized with glucose oxidase (GOx) by chemical cross‐linking to obtain GOx/FWCB. Moreover, the key parameters for FWCB fabrication are optimized, and the sensing strategy of the proposed GOx/FWCB is also investigated. The results show that the proposed GOx/FWCB can be used for the detection of glucose in the range of 0.01–3.0 mM with satisfactory selectivity, and the limit of detection (LOD) is calculated to be as low as 0.8 µM (S/N = 3). These dramatic advantages endow the proposed FWCB with broad application prospects in the field of portable, wearable, and real‐time detection of glucose in human sweat for health monitoring.

Universal Strategy for Reversing Aging and Defects in Graphene Oxide for Highly Conductive Graphene Aerogels.

The production of highly stable, defect-free, and electrically conducting 3D graphene structures from graphene oxide precursors is challenging. This is because graphene oxide is a metastable material whose structure and chemistry evolve due to aging. Aging changes the relative composition of oxygen functional groups attached to the graphene oxide and negatively impacts the fabrication and properties of reduced graphene oxide. Here, we report a universal strategy to reverse the aging of graphene oxide precursors using oxygen plasma treatment. This treatment decreases the size of graphene oxide flakes and restores negative zeta potential and suspension stability in water, enabling the fabrication of compact and mechanically stable graphene aerogels using hydrothermal synthesis. Moreover, we employ high-temperature annealing to remove oxygen-containing functionalities and repair the lattice defects in reduced graphene oxide. This method allows obtaining highly electrically conducting graphene aerogels with electrical conductivity of 390 S/m and low defect density. The role of carboxyl, hydroxyl, epoxide, and ketonic oxygen species is thoroughly investigated using X-ray photoelectron and Raman spectroscopies. Our study provides unique insight into the chemical transformations occurring during the aging and thermal reduction of graphene oxide from room temperature up to 2700 °C.