Reduced Graphene Oxide Films Research Articles

Preparation of High Thermal Conductivity Graphene Films by Rapid Reduction with Low Energy Consumption.

In the domain of smart electronic devices, graphene films play a pivotal role due to their flexibility and high thermal conductivity. Within the realm of fabricating highly thermally conductive graphene films, Joule heating technology has garnered significant attention because of its capability for rapid temperature elevation and reduction of graphitization duration. However, substantial gas emission occurs during the reduction of graphene oxide films using this method, leading to immediate combustion and film fracturing, thereby limiting the rapid and uninterrupted production of graphene films. To address this challenge, a rapid reduction preparation process is introduced. This process initiates with a two-step reduction of graphene oxide films employing a reducing agent to establish gas escape pathways within the graphene films beforehand. Subsequently, the film is pressurized and Joule-heated using a graphite plate, with the entire heating process lasting only 800 s. The resulting graphene film exhibits a remarkable thermal conductivity of up to 1012W/(m·K). This method enhances the production efficiency of high thermal conductivity graphene films and is expected to further reduce production costs.

Dual‐active‐layer flexible piezoresistive sensor based on wrinkled microstructures and electrospun fiber network for human‐related motion sensing applications

AbstractFlexible pressure sensors with high sensitivity and a wide detection range must be developed for practical applications. In this study, a dual‐active‐layer flexible piezoresistive sensor was developed. A reduced graphene oxide film with wrinkled microstructures was prepared by a simple and low‐cost substrate pre‐stretching method and used as the first active layer. A thermoplastic polyurethane electrospun fiber membrane was modified by fast polydopamine coating and ultrasonication with multi‐walled carbon nanotubes and used as the second active layer. Owing to the continuously changing conductive pathways created by the wrinkled microstructures and fiber network under pressure deformation, the sensor achieved a detection range of 0–100 kPa, with sensitivities of 8.5, 1.35, and 0.39 kPa−1 in the ranges of 0–1, 1–20, and 20–100 kPa, respectively. Additionally, the sensor exhibited a low detection limit (2 Pa), response and recovery times of 105 and 85 ms, respectively, and reliable service performance over 10,000 loading/unloading cycles. The sensor enabled real‐time monitoring of finger and wrist bending, beaker‐holding, and fingertip‐sliding on a touch screen, demonstrating its feasible applications in wearable electronics and human–machine interface devices.

Low-energy argon ion beam irradiation for the surface modification and reduction of graphene oxide: Insights from XPS

Developing environmentally friendly methods for reducing graphene oxide (GO) is essential. This study investigates the surface modification and reduction of GO films using 200 eV argon ion (Ar+) beam irradiation. X-ray Photoelectron Spectroscopy (XPS) analysis reveals significant chemical changes on the GO surface. GO was irradiated with a 200 eV Ar+beam for varying times (0–80 s). XPS survey spectra showed the presence of carbon and oxygen, with an increasing carbon atomic percentage over time. High-resolution XPS spectra of C 1s revealed peaks corresponding to sp2, C–OH, O–C–O, CO, and O–CO bonds. In the O 1s spectra, CO, O–C–O, and C–OH groups were observed. Upon irradiation, the CO peak consistently decreased, the O–C–O peak fluctuated, and the C–OH peak increased, indicating effective reduction of CO groups, dynamic changes in O–C–O functionalities, and the formation of additional C–OH groups. The C/O ratio increased from ∼2.4 to 2.7, underscoring the reduction process and enhanced carbon content. This method proves to be an efficient approach for producing reduced graphene oxide (rGO) with improved properties for advanced applications.

Reduced graphene oxide film modified by tannic acid for high areal performance supercapacitors

Reduced graphene oxide film modified by tannic acid for high areal performance supercapacitors

Reduced Graphene Oxide Films to Enhance the Tribological Performance of Micro-arc Oxidation Coatings

Reduced Graphene Oxide Films to Enhance the Tribological Performance of Micro-arc Oxidation Coatings

Significantly enhanced photo response of hydrazine hydrate reduced graphene oxide films modified with swift heavy ion irradiation of silver (Ag8+) ions

In this paper, a multistep reduction process of graphene oxide (GO) is discussed. It is basically a two-step reduction process. In the first step, the GO sample is reduced by hydrazine hydrate. In the second step, it is further reduced by a swift heavy ion irradiation beam of silver (Ag8+) ions of 100 MeV energies. Ion beam irradiation causes defects in the hydrazine hydrate reduced graphene oxide (rGO) samples. FTIR study confirms the removal of oxygen containing functional groups. The pore volume and pore density of the samples seem to increase with increase in the ion irradiation doses. It is also seen that the electrical conductivity and specific surface area increases with dose of ion irradiation. The prepared samples were tested for photo response measurement and among all the sample, R5 had the highest photo response of 6.25 % at 30 mW/cm2. The photodetection response seems to increase with increase in intensity of light.

Reduction of graphene oxide film on glass substrate using argon ion beam irradiation: A systematic study with X-ray photoelectron spectroscopy analysis

In our research, we explored a novel and eco-friendly method of utilizing argon ion beam irradiation to thin down graphene oxide (GO) films on glass substrates, aiming to enhance their mechanical, electrical, and optical properties. By employing high-energy argon ions, we developed a groundbreaking, environmentally conscious technique that not only permits micro-patterning directly on GO films but also facilitates concurrent material characterization. Varying the energy levels (1000, 2000, and 3000 eV) and exposure times (0 to 80 s, in 20-second increments), we meticulously examined the impact on carbon and oxygen atomic ratios of the GO using X-ray photoelectron spectroscopy (XPS) for in-depth analysis. Our findings revealed that increasing the argon ion beam energy to 2000 eV and extending the irradiation time significantly reduced oxygen content while increasing the carbon atomic ratio, indicating effective GO surface reduction. However, further increasing the energy to 3000 eV resulted in a slight increase in oxygen content and a decrease in the carbon atomic ratio compared to the energy 2000 eV, suggesting a decrease in reduction efficacy. This method's simplicity, eco-friendliness, and precision mark a significant advancement over traditional chemical reduction methods, offering a solid understanding of high-energy argon ion beam irradiation's effectiveness in GO reduction. Our comprehensive analysis, including survey and high-resolution C 1s and O 1s XPS spectra, highlights the surface chemistry modifications induced by this treatment, demonstrating the versatility of argon ion beam irradiation in producing reduced graphene oxide (rGO) for various applications.

Effect of supporting layer on electrical characteristics of field-effect transistor based on reduced graphene oxide film

The field-effect transistors (FETs) based on reduced graphene oxide (rGO) with SiO2, porous silicon (PS), and oxidized porous silicon (PSox) supporting layers were obtained. The influence of charged impurities in the silicon substrate and electrically active defects in the support layers on the electrical properties of the FETs was studied based on the capacitance-voltage characteristic analysis. Localized electron states in the SiO2, PS, and PSox supporting layers that affect the charge transfer in the rGO-based FETs were determined using thermally stimulated depolarization spectroscopy. The influence mechanisms of various supporting layers on the electrical characteristics of the obtained FETs are discussed.

Enhanced Electron Transfer Efficiency of Fructose Dehydrogenase onto Roll-to-Roll Thermal Stamped Laser-Patterned Reduced Graphene Oxide Films.

Herein, a strategy to stamp laser-produced reduced graphene oxide (rGO) onto flexible polymers using only office-grade tools, namely, roll-to-roll thermal stamping, is proposed, proving for the first time its effectiveness for direct bioelectrocatalysis. This straightforward, scalable, and low-cost approach allows us to overcome the limits of the integration of laser-induced rGO-films in bioanalytical devices. Laser-produced rGO has been thermally stamped (TS) onto different polymeric substrates (PET, PVC, and EVA) using a simple roll-laminator; the obtained TS-rGO films have been compared with the native rGO (untransferred) via morphochemical and electrochemical characterization. Particularly, the direct electron transfer (DET) reaction between fructose dehydrogenase (FDH) and TS-rGO transducers has been investigated, with respect to the influence of the amount of enzyme on the catalytic process. Remarkable differences have been observed among TS-rGO transducers; PET proved to be the elective substrate to support the transfer of the laser-induced rGO, allowing the preservation of the morphochemical features of the native material and returning a reduced capacitive current. Noteworthily, TS-rGOs ensure superior electrocatalysis using a very low amount of FDH units (15 mU). Eventually, TS-rGO-based third-generation complete enzymatic biosensors were fabricated via low-cost benchtop technologies. TS-rGOPET exhibited bioanalytical performances superior to the native rGO, allowing a sensitive (0.0289 μA cm-2 μM-1) and reproducible (RSD = 3%, n = 3) d-fructose determination at the nanomolar level (LOD = 0.2 μM). TS-rGO exploitability as a point-of-need device was proved via the monitoring of d-fructose during banana (Musa acuminata) postharvest ripening, returning accurate (recoveries 110-90%; relative error -13/+1%) and reproducible (RSD ≤ 7%; n = 3) data.

Facile preparation and broadband microwave absorption of multilayered materials based on thin films of reduced graphene oxide

Microwave absorption (MA) materials have received extensive attention for their wide applications in both civil and military areas. However, many MA materials have a large thickness, high filling ratio, and narrow effective microwave absorption bandwidth (Reflection Loss, RL ≤ −10 dB) (EAB), and are prepared by complex processes. In this work, a reduced graphene oxide (RGO) film is prepared for the first time by an approach involving floating-dipping and chemical reduction. Compared with previous micrometers-thick RGO films, the present 200 nm-thick dense RGO film is critical for improving not only the impedance matching but also the capability of the material to attenuate incident microwaves. Based on such a thin RGO film, a multilayered material with a jaaumann structure is constructed with individual RGO layers alternating between low dielectric polyethylene terephthalate (PET) sheets. With the superb impedance matching, multilayer attenuation, and multi-cavity resonance, the present multilayered material can achieve a wide EAB of 13.75 GHz with a minimum reflection loss of −47.69 dB using only 3 layers of RGO films. This study provides a new and simple strategy for the development of layered materials with a thin thickness, low filling ratio, and strong absorption with a wide EAB.

Preparation of Reduced Graphene Oxide Films with High and Uniform Thickness for Electromagnetic Interference Shielding

Reduced graphene films have attracted widespread commercial interest due to high electrical conductivity toward (EMI) shielding. At present, the preparation path of reduced graphene film is to use graphene oxide (GO) as the raw material through self-assembly and high-temperature heat treatment. However, the thickness of reduced graphene films is not high and uniform because of the higher mobility of the graphene oxide slurry, which destroys the reliability of the membrane in the field of electromagnetic interference shielding. Here, we propose the use of sodium carboxymethyl cellulose (CMC) to increase the viscosity of graphene oxide to prepare reduced graphene films with high and uniform thickness. After modification with sodium carboxymethyl cellulose, the EMI shielding effectiveness (EMI SE) of reduced graphene oxide films stabilized at 91–96 dB at 8–12 GHz, which is higher than pure graphene films. Meanwhile, the addition of CMC does not affect the structure of reduced graphene films. This work broadens the application of reduced graphene films in electromagnetic shielding.

Activity and stability of electrochemically reduced graphene oxide films for applications requiring mixed conductivity

A protonic and electronic conductor composed of partially reduced graphene oxide (GO) has been prepared by electrochemical methods. Conductivity measurements and detailed surface analysis by XPS, FTIR, and Raman methods show that the electrochemically reduced GO (ERGO), prepared under different reduction potentials, exhibits a unique dual (protonic and electronic) conductivity which is tunable by adjusting the surface conditions. Selected removal of the oxygenated groups, evolution of C(sp2)/C(sp3) hybrid carbon structure, and surface structure of ERGO can impact the protonic and electronic transport mechanisms. The ERGO samples reported here are ideal support materials with proper ratios of protonic and electronic transport. The as-prepared ionomer-free and flexible ERGO-supported Pt (Pt/ERGO) electrodes were characterized for oxygen reduction reaction (ORR) reactivity in acidic solution. The results showed not only higher electrochemical surface area (ECSA), but also improved mass activity towards ORR compared to conventional carbon supported Pt catalysts.

Self-assembled graphene oxide thin films deposited by atmospheric pressure plasma and their hydrogen thermal reduction

This work uses an atmosphere-pressure plasma jet to obtain thin, homogeneous graphene oxide coatings. The films consisted of self-assembled graphene oxide (GO) layers, which were reduced by heat treatment under a reductive hydrogen atmosphere to obtain a reduced graphene oxide film. The electrochemical and photoelectrochemical analyses show that electrical conductivity increases after the reduction process; meanwhile, this process eliminates the p-type photoactivity of the graphene oxide film. The reduced graphene oxide X-ray diffraction pattern revealed the elimination of the signal at 2θ = 11° initially found in the graphene oxide film. The C1s and O1s high-resolution XPS analyses of the reduced graphene oxide film reveal a pronounced increase in the graphitic-like carbon (sp2), whereas a decrease in the organic-like carbon (sp3) and oxygenated species, such as C-OH, C-O-C, CO, and OCOH, initially found in the graphene oxide film.

Shellac-mediated laser-induced reduced graphene oxide film on paper and fabric: exceptional performance in flexible fuel cell, supercapacitor and electrocardiography applications

Natural biopolymer (shellac and dewaxed shellac) supported one-step laser-induced conductive rGO patterns (lowest sheet resistance of ∼2.3 Ω Sq.−1). Enormous potential applications in wearable, flexible, energy storage and biomedical fields.

Improved field emission properties of reduced graphene oxide decorated with indium nanoparticles

Low work function metals decoration of graphene is a effective method for the improvement of electron field emission properties. Indium, a relatively lower work function metal, is used to decorate reduced graphene oxide (RGO) films for the first time by simple and efficient solution process combined with magnetron sputtering method and the field emission properties are investigated. At continue voltage mode, the indium decorated RGO films display lower turn-on and threshold field as well as better emission stability than those of pristine RGO films. Moreover, the field emission performance of indium decorated RGO films is affected by the spacing between the cathode and anode. At pulse voltage mode, the indium decorated RGO films show approximately 10 times higher maximum emission current density compared to that at continue voltage mode. The calculation results by density functional theory indicate that the indium decoration of RGO significantly increases the density of states (DOS) near Fermi level and reduces the work function.

Triboelectric Nanogenerator Prepared from Poly(vinylidene Fluoride-Hexafluoropropylene) Polymer Composite

In this work, poly(vinylidene fluoride-hexafluoropropylene)/reduced graphene oxide films were prepared by the solution casting method with N,N-dimethylformamide (DMF) and DMF/acetone mixed solvents. The effects of reduced graphene oxide and solvent type on the morphology and crystal structure of the composite films were investigated by using scanning electron microscopy, Fourier-transform infrared spectroscopy, and Raman spectroscopy, respectively. The morphology study showed that the addition of acetone in the film process resulted in the occurrence of tiny pores on the film surfaces. The reduced graphene oxide incorporated into the PVDF-HFP was able to promote the formation of β- phase in the composites. The maximum power of 15.58 µW was obtained from the films using DMF/acetone mixture as solvent.

Fabrication of Hydroxyl‐Group‐Rich Reduced Graphene Oxide Film and its Application for Electrochemical Detection of Hydrogen Peroxide

AbstractGraphene oxide (GO) can be obtained economically from graphite, and it has, therefore, been used for energy storage, conversion, and biosensor fabrication. To overcome the limitations associated with the poor electrical conductivity of GO, mild thermal reduction is widely used. However, owing to considerable variations in GO in terms of size and shape, uniform reduction of GO films is highly challenging. Herein, it reports a mildly reduced uniform graphene oxide thin film (mrUG) that is enriched with functional hydroxyl groups. This film is effective for electrochemical H2O2 decomposition and detection. A uniform graphene oxide thin film (UGTF) is first fabricated on an indium tin oxide (ITO) substrate and subjected to mild thermal annealing at 300 °C. Remarkably, the variations in all important parameters, including film thickness, surface roughness, reduction level, are significantly low in the case of mrUG. Moreover, It is found that unlike GO, UGTF undergoes structural rearrangement easily and possesses many hydroxyl groups (─OH) when reduced for a specific duration (t = 10 s, mrUG(10)). mrUG(10) is highly stable and effectively decomposed H2O2, which is advantageous for the electrochemical detection of H2O2 with extremely low signal variations. Therefore, mrUG(10) can be used as a carbon‐based metal‐free electrocatalyst in biosensors, energy, and electronic applications.

Wearable Temperature Sensors Based on Reduced Graphene Oxide Films.

With the development of medical technology and increasing demands of healthcare monitoring, wearable temperature sensors have gained widespread attention because of their portability, flexibility, and capability of conducting real-time and continuous signal detection. To achieve excellent thermal sensitivity, high linearity, and a fast response time, the materials of sensors should be chosen carefully. Thus, reduced graphene oxide (rGO) has become one of the most popular materials for temperature sensors due to its exceptional thermal conductivity and sensitive resistance changes in response to different temperatures. Moreover, by using the corresponding preparation methods, rGO can be easily combined with various substrates, which has led to it being extensively applied in the wearable field. This paper reviews the state-of-the-art advances in wearable temperature sensors based on rGO films and summarizes their sensing mechanisms, structure designs, functional material additions, manufacturing processes, and performances. Finally, the possible challenges and prospects of rGO-based wearable temperature sensors are briefly discussed.

Development of Hybrid Electrodes Based on a Ti/TiO2 Mesoporous/Reduced Graphene Oxide Structure for Enhanced Electrochemical Applications

Titanium/TiO2 mesoporous/reduced graphene oxide structure for construction of a hybrid electrode was successfully developed using a facile and effective spin-coating technique. The as-prepared structures were characterized using ultraviolet-visible spectroscopy (UV-Vis), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, RAMAN analysis, scanning electron microscopy (SEM) coupled with elemental analysis (EDX), and atomic force microscopy (AFM). In addition, the electrochemical behavior was assessed by cyclic voltammetry (CV) in a 1M KNO3 supporting electrolyte and in the presence of 4 mM K3Fe(CN)6 to determine the electroactive surface area and apparent diffusion coefficient of the hybrid electrode. The charge transfer resistance was investigated via electrochemical impedance spectroscopy (EIS) in a 0.1 M Na2SO4 supporting electrolyte to confirm the role of reduced graphene oxide on the electrode’s surface. The potential application of as-obtained hybrid electrodes in electroanalysis was tested through cyclic voltammetry in the presence of doxorubicin as the target analyte, in the concentration range between 1 to 7 mg L−1 DOX. By using mesoporous TiO2 with a high specific surface area (~140 m2 g−1) in the synthesis of the composite material based on a Ti/TiO2(Ms)/rGO hybrid structure, was obtained a 2.3-times increase in electroactive surface area than the geometrical surface area of the hybrid electrode. These results provide new insights into the development of high-performance and cost-effective electrochemical sensors based on reduced graphene oxide films on metallic structures for applications in the detection processes of drugs from wastewater.

Low-cost synthesis of titanium dioxide nanotubes/reduced graphene oxide heterostructure for pH sensor applications

In this work, we deposit Graphene Oxide (GO) films on Titanium Dioxide nanotubes (TiO2NTs); electrochemical characterization of this system shows that this structure has potential applications as a pH sensor. TiO2NTs were obtained by electrochemical anodization technique, the GO was fabricated by modified Hummer's method, and deposited by dip coating technique, at room temperature. The thermally treated TiO2NTs/GO structure shows a reduction of the GO deposited film. The samples were characterized by Raman spectroscopy, X-ray Photoelectron Spectroscopy, and Scanning Electron Microscopy. Depending on the GO oxidation time and thermal treatment, we observe a uniform reduced GO film on the TiO2NTs. A pH electrode characterization shows a linear response of the TiO2NTs/GO of 57 mV/pH with non-hysteresis effect.