Functional Groups Of GO Research Articles

2D Electrodes From Functionalized Graphene for Rapid Electrochemical Gold Extraction and Reduction From Electronic Waste.

Electronic waste (e-waste) contains substantial quantities of valuable precious metals, particularly gold (Au). However, inefficient metal recovery leads to these precious metals being discarded in landfills, causing significant water and environmental contamination. This study introduces a two-dimensional (2D) electrode with a layered graphene oxide membrane functionalized by chitosan (GO/CS). The GO/CS membrane acts as an ion-selective layer and demonstrates capabilities in the electrochemical extraction and reduction of Au ions. The multiple functional groups of GO and CS offer high cooperativity in ion extraction and reduction, achieving 95wt.% extraction efficiency within 10min. The simultaneous extraction and electrocatalytic reduction of Au ions within the membrane leads to the formation of ready-to-use metallic Au forms such as chips and sensors. Such an approach eliminates the processing steps required to convert extracted gold into functional products, reducing time, cost, and energy. This direct formation of usable Au components enhances the efficiency of the recovery process, making it economically viable and environmentally sustainable. The gold mining market is projected to be valued at $270 billion by 2032, with the recycling segment reaching $10.8 billion, highlighting the substantial benefits and economic potential of efficient e-waste recycling technologies.

Microdrop InkJet printed supercapacitors of graphene/graphene oxide ink for flexible electronics

The inkjet printing (IJP) technique is a highly promising technology for fabricating flexible electronics for wearable applications. The latest Microdrop IJP technology was introduced to produce flexible supercapacitors using a readily prepared graphene/graphene oxide ink. Molecular modelling concepts were conducted prior to ink formulation to investigate the interaction between graphene and GO via adsorption interactions to investigate the feasibility of adding GO to G for energy storage processes. Calculations validate that their interaction yields stable, highly reactive, and conductive structures. Molecular electrostatic potential maps reveal excellent charge distribution proposing G/GO as a potential candidate for electrochemical processes. Subsequently, GNPs/GO blend was prepared, leveraging the electric conductivity and high surface area of graphene, and the functional groups in GO to enhance graphene dispersion. Simple and interdigitated supercapacitor electrodes were fabricated without further post-printing complexities. The highly flexible interdigitated supercapacitor (100L) demonstrated notable performance with areal capacitance of 195.1 F m−2 at 0.4 A.m−2, power density of 1199.34 mW m−2, energy density of 24.91 mWh.m−2, and 80.65 % capacitance retention after 5000 cycles. The outstanding electrocapacitive performance was ascribed to GO's abundant functional groups and its 3D open structure. These factors contribute to adding a pseudocapacitive effect and enhancing charge transfer within the electrode channel-like networks.

Compositional effects of hybrid MoS2–GO active layer on the performance of unipolar, low-power and multistate RRAM device

Currently, 2D nanomaterials-based resistive random access memory (RRAMs) are explored on account of their tunable material properties enabling fabrication of low power and flexible RRAM devices. In this work, hybrid MoS2–GO based active layer RRAM devices are investigated. A facile hydrothermal co-synthesis approach is used to obtain the hybrid materials and a cost-effective spin coating method adopted for the fabrication of Ag/MoS2–GO/ITO RRAM devices. The performance of the fabricated hybrid active layer RRAM device is analysed with respect to change in material properties of the synthesized hybrid material. The progressive addition of 0.5, 1.5, 2.5 and 4.5 weight % of GO to MoS2, results in a hybrid active layer with higher intermolecular interaction, in the case of Ag/MoS2–GO4.5/ITO RRAM device, resulting in a unipolar resistive switching RRAM behavior with low SET voltage of 1.37 V and high I on/I off of 200 with multilevel resistance states. A space charge limited conduction mechanism is obtained during switching, which may be attributed to the trap states present due to functional groups of GO. The increased number of conduction pathways on account of both Ag+ ions and oxygen vacancies (Vo 2+), participating in the formation of conducting filament, results in higher I on/I off. This is the first report of unipolar Ag/MoS2–GO/ITO RRAM devices, which are particularly important in realizing high density crossbar memories for neuromorphic and in-memory computing as well as enabling flexible 2D nanomaterials-based memristor applications.

A Comparative Study of the Effect of Oxygen-Containing Functional Groups in GO and rGO Sheets Decorated with Small Gold Nanoparticles on Bioactivities

A Comparative Study of the Effect of Oxygen-Containing Functional Groups in GO and rGO Sheets Decorated with Small Gold Nanoparticles on Bioactivities

Self-responsive H2-releasing microneedle patch temporally adapts to the sequential microenvironment requirements for optimal diabetic wound healing

Oxidative stress regulation and synchronized promotion of angiogenesis are critical factors in the healing process of diabetic wounds. However, existing research often fails to fully consider the dynamic interplay between these two biological processes and their time-dependent roles in diabetic wound healing. This study innovatively introduces a novel hydrogen (H2)-releasing microneedle patch capable of precisely controlling the regulation of oxidative stress and the promotion of angiogenesis through a bidirectional responsive mechanism of microneedles and backing layers. Specifically, we employ ammonia borane (AB)-loaded mesoporous silica nanoparticles (MSN) as a source of H2, combined with polyvinyl pyrrolidone (PVP) to fabricate microneedles. This design effectively clears excessive reactive oxygen species (ROS) in deep tissues and promotes the M2 polarization of macrophages. Concurrently, we utilize cobalt-adsorbed graphene oxide (GO/Co2+) mixed with polyvinyl alcohol (PVA) to prepare backing layers, which not only release Co2+ upon the reduction of oxygen-containing functional groups in GO by H2 diffused from deep tissues to synergize with H2 for enhanced vascularization, but also endow the microneedle patch with near-infrared (NIR) light-responsive antimicrobial properties, crucial for managing diabetic infected wounds. Through this innovative dual-action mechanism, our research significantly accelerates the healing process of infected wounds in a diabetic mouse model. Moreover, single-cell sequencing results further confirm the pivotal role of H2 in regulating oxidative stress, promoting macrophage M2 polarization, and stimulating angiogenesis. These results not only showcase the unique features of our microneedle patch but also offer new perspectives and therapeutic strategies for the treatment of diabetic wounds.

An in-sensor humidity computing system for contactless human-computer interaction.

Being capable of processing large amounts of redundant data and decreasing power consumption, in-sensor computing approaches play significant roles in neuromorphic computing and are attracting increasing interest in perceptual information processing. Herein, we proposed a high performance humidity-sensitive memristor based on a Ti/graphene oxide (GO)/HfOx/Pt structure and verified its potential for application in remote health management and contactless human-machine interfaces. Since GO possesses abundant hydrophilic groups (carbonyl, epoxide, and hydroxyl), the memristor shows a high humidity sensitivity, fast response, and wide response range. By utilizing the proton-modulated redox reaction, humidity exposure to the memristor induces a dynamic change in the switching between high and low resistance states, ensuring essential synaptic learning functions, such as paired-pulse facilitation, spike number-dependent plasticity, and spike amplitude-dependent plasticity. More importantly, based on the humidity-induced salient features originating from the abundant hydrophilic functional groups in GO, we have implemented a noncontact human-machine interface utilizing the respiratory mode in humans, demonstrating the potential of promoting health monitoring applications and effectively blocking virus transmission. In addition, the high recognition accuracy of contactless handwriting in a 5 × 5 array artificial neural network was successfully achieved, which is attributed to the excellent emulated synaptic behaviors. This study provides a feasible method to develop an excellent humidity-sensitive memristor for constructing efficient in-sensor computing for application in health management and contactless human-computer interaction.

Graphene-supported Cu2O-CoO heterojunctions for high performance supercapacitors

Transition metal oxides are excellent electrode materials for supercapacitors because of their high theoretical capacitance, good stability, environmental friendliness, and tunable structure. In this study, Cu2O-CoO heterojunction materials loaded on graphene oxide (Cu2O-CoO/GO) are prepared via the precipitation, hydrothermal, and heat treatment processes. Through the adsorption of transition metal ions by the oxygen-containing functional groups of GO, followed by alkali titration as well as hydrothermal reaction of Cu2+ and Co2+ ions, the hydroxides of metals are adsorbed on GO. Meanwhile, the reduced GO completes the self-assembly, and the GO with good spatial structure supports the formation of Cu2O-CoO heterojunction structure. The Cu2O-CoO/GO electrode material combines the high conductivity of GO with the excellent internal conductivity of Cu2O-CoO, and its abundant active sites and specific surface area, thereby ensuring good electrochemical performance. Thus, it enables reversible ion adsorption and desorption, exhibits the pseudocapacitance of copper oxide and cobalt oxide, and has higher capacitance performance than Cu2O/GO and CoO/GO electrodes. The specific capacitance of Cu2O-CoO/GO at 1 A g−1 is 723 F g−1. Cu2O-CoO/GO/ASC exhibits an energy density of 44.1 Wh kg−1 at 794 W kg−1 and capacitance retention rate of 89.3 % after 10,000 cycles. This indicates that the material has significant potential for a wide range of supercapacitor applications.

Room-temperature flexible ammonia sensor based on SnO2 quantum dots modified graphene oxide

Tin dioxide quantum dots (SnO2 QD) were prepared by hydrothermal method, and then SnO2 QD modified graphene oxide (SnO2 QD@GO) was synthesized by a secondary hydrothermal technique to fabricate a flexible sensor for detecting ammonia at room temperature. The morphology, structure and composition of the composites were analyzed by SEM, TEM, EDS, XPS, XRD and Raman spectroscopy. TEM images showed that SnO2 QD with a diameter range of 5–8 nm present a cuboid structure, embedded in the two-dimensional GO surface. The gas sensing test shows that at room temperature the response of SnO2 QD@GO to ammonia is 5 times higher than that of GO. At the same time, the operating temperature of pure SnO2 QD is greatly reduced from 250 °C to room temperature (24 °C) by the composing of GO. Flexibility test of SnO2 QD@GO was also measured to test the fatigue resistance and bending test of the device. The improved ammonia sensing performance of SnO2 QD@GO is mainly due to the smaller bond energy of ammonia and abundant functional groups of GO, which provides more active sites for the surface adsorption of NH3.

A flexible humidity sensor constructed by ordered-pore-array of slightly reduced graphene oxide with much enhanced sensing response

Reduced graphene oxide (rGO) flexible film humidity sensor has received increasing attention, but the low sensing response caused by lack of available hydrophilic functional groups is still a limitation. Herein, a slightly reduced graphene oxide (SrGO) ordered-pore-array, fabricated via a monolayer colloid crystal template method, was introduced as a resistive humidity sensor. It was obtained based on adsorption between the GO sheets and the template microspheres, in-situ slight reduction of the GO shells and the removal of template. The reduction way allows the functional groups of GO to be retained as much as possible, and the unique structures (e.g., spherical double surfaces and small through-holes on pore-walls) facilitate the substantial exposure of functional groups, the penetration of water molecules and the utilization of buried functional groups. The available functional groups are thereby efficiently increased, giving the sensor an unprecedented high sensing response, more than 2600 times the maximum response of existing rGO sensors. The sensor also demonstrated excellent practical characteristics, and by detecting a single exhale, it could be employed in quick and quantitative evaluation of human activities and health. This strategy paves a facile and promising route to improve the sensing response and application of graphene-based humidity sensors or gas sensors.

One step biosynthetic mechanism of hybrid reduced graphene oxide/Mn nanoparticles used for simultaneous removal antibiotics

Recently, green synthetic technology has attracted much attention due to its low cost, waste-reuse and environmental friendliness. In this study, reduced graphene oxide/manganese nanoparticles hybrids (rGO/Mn NPs) were successfully synthesized utilizing green tea extract by one-step method. The rGO/Mn NPs were characterized by SEM-EDS, XRD, Raman, FTIR and BET, and the results indicate oxygen-containing functional groups in GO were effectively removed. Also, manganese nanoparticles (Mn NPs) were uniformly decorated on the rGO surface, and rGO/Mn NPs hybrids exhibited a lamellar sandwich structure, which was improve the specific surface area and provide more adsorption sites. The biomolecules in tea extract were further identified by GC–MS analysis, where showed that 1,2,3-trichlorophenol, caffeine and antioxidant were involved to the biosynthesis. Furthermore, the rGO/Mn NPs were used to simultaneously remove oxytetracycline/tetracycline (OTC/TC) with more than 90% of the removal efficiency, demonstrating that rGO/Mn NPs have a potential for treating antibiotic wastewater.

Synthesis and characterization of nano-fibres graphene oxide for sensing humidity

Relative humidity is the prime parameter in industrial processes which are measured through ceramic, metal oxide and polymeric sensors. Ceramic and metal oxide sensors shows nonlinear resistive behaviours with increasing relative humidity and high sintering temperature for hydro-desorption. Transformation of ceramic and metallic sensors with the polymeric sensors is due to its eco-friendly synthesis fabrication, less heat intensive and high sensitivity. In this research work, a polymeric sensor of enhanced electric properties with sustainable captive and resistive response was synthesised from nano-fibres graphene oxide for sensing humidity. The synthesized graphene oxide through modified Hammer method was mixed with poly-vinyl alcohol (GO/PVA) in the ratio of 5 wt % for four hours at 90 ºC. Nano fibres of graphene oxide and poly-vinyl alcohol (GO/PVA) solutions were obtained at the 24V DC electric field; 0.5 ml/h feed rate and 10 cm tip-to-collector distance through electrospinnig. GO/PVA fibres were deposited on the silver inter-digited electrodes of 8mm and five combs of 20Îm consecutive distance. SEM analysis shows that the fibres were in nano-range with no major cracks while XRD and FTIR spectrum investigated the finger prints and functional groups of GO and GO/PVA respectively. Parametric study of resistive and capacitive were analysed at difference response and recovery time at various frequency in the range of 0 % to 82% relative humidity.

Lightweight Porous Polyurethane Foam Integrated with Graphene Oxide for Flexible and High-Concentration Hydrogen Sensing.

Reliable detection of high-concentration hydrogen (H2) leakage in sharp-vibration environments is highly desired such as in the application of space rockets. As hydrogen has to be detected simultaneously in a wide concentration range and at high concentrations (e.g., 100 v/v%) with outstanding linearity in response/concentration, lightweight features, and excellent tolerance against saturation and vibration, it remains challenging. Here, a flexible and high-concentration H2 sensing has been developed through "dipping-drying" a three-dimensional (3D) porous polyurethane (PU) foam integrated with graphene oxide (GO-PU). Multilayered honeycomb-structured graphene oxide appears to be tightly adhered to faveolate PU. Benefiting from the numerous adsorption sites of the "dual honeycomb" structure and abundant surface functional groups of GO, the GO-PU foam exhibits distinguished response and linearity toward 2-100 v/v% H2 and shows excellent lightweight, tailorability, and flexibility. Remarkably, the foam possesses outstanding sensing stability against 0-180° bending and low 0-20% straining, along with outstanding H2 sensing performance even after being pressed by a weight of 200 g, immersed in water, and frozen in a refrigerator at -10.8 °C. Practically, the GO-PU foam has potential for high-concentration H2 leakage detection, and our synthetic strategy may provide a way to avoid adsorbing saturation in other flexible gas sensing.

RGO-loaded double phase Mo-doped NiS for enhanced battery-type energy storage in hybrid supercapacitors

The Mo-doped NiS/rGO composite was obtained by vulcanization of NiMoO4 and morphology adjustment by GO. A nanosheet-like structure was demonstrated in the composite, which was assembled by double-phase Mo-doped NiS (Mo-NiS) nanodots loading on reduced graphene oxide (rGO) nanosheets. The doping of Mo and the resultant synergistic effect between Mo and Ni can offer the bimetallic sulfide of Mo-NiS with higher capacity output and enhanced cycle stability. The surface oxygen-containing functional groups of GO provide abundant nucleation centers for the uniform loading of Mo-NiS nanodot during synthesis, and the resultant rGO sheets in the final composite ensures continuous electron transport and promoted ionic exchange for Mo-NiS. Besides, the Mo-NiS nanoparticles loaded on the surface of rGO can also inhibit its stacking and form a highly integrated composite structure. The synergistic effect of Mo-doping, double-phase NiS and conductive rGO substrates attributed to the high specific capacity output (1664.7 C g−1 at 1 A g−1), long cycle life and excellent rate performance in the final composite. The Mo-NiS/rGO composite was also applied as a battery-type electrode in asymmetric supercapacitors (ASCs), which showed acceptable performance for potential practicability, including attractable energy densities and power densities, as well as impressive cyclic ability with large capacity retention of 90.3% in 7000 cycles.

Fabrication of octahedral GO/UiO-67@PtNPs nanocomposites as an electrochemical sensor for ultrasensitive recognition of arsenic (III) in Chinese Herbal Medicine

The pharmacological research and detection of heavy metals of Chinese Herbal Medicines (CHMs) are important for environmental protection and human health. Here, a novel electrochemical sensor has been proposed for the detection of arsenic (As (Ⅲ)) in CHMs. The sensing system was constructed based on the octahedral GO/UiO-67@PtNPs composites, which had a porous structure with a large, unique surface area and was conducive to the adsorption and enrichment of As (Ⅲ). The oxygen-containing functional groups of GO immobilized As (Ⅲ) metal ions and its own electrical conductivity, and nanoparticles (PtNPs) have electrocatalytic effects on As (Ⅲ), which can accelerate electron transfer and increase the abundance of active sites. Under the optimized conditions, the homemade electrode showed excellent electrochemical properties, satisfactory linear range (2.7–40 nM), and a lower limit of detection (LOD, 0.42 nM). It might be low-cost, rapid, sensitive, and quantitatively identified of As (Ⅲ) in various environmental samples, especially in the medical field.

Nano Carbon Doped Polyacrylamide Gel Electrolytes for High Performance Supercapacitors.

Novel polyacrylamide gel electrolytes (PGEs) doped with nano carbons with enhanced electrochemical, thermal, and mechanical properties are presented. Carboxylated carbon nanotubes (fCNTs), graphene oxide sheets (GO), and the hybrid of fCNT/GO were embedded in the PGEs to serve as supercapacitor (SC) electrolytes. Thermal stability of the unmodified PGE increased with the addition of the nano carbons which led to lower capacitance degradation and longer cycling life of the SCs. The fCNT/GO-PGE showed the best thermal stability, which was 50% higher than original PGE. Viscoelastic properties of PGEs were also improved with the incorporation of GO and fCNT/GO. Oxygen-containing functional groups in GO and fCNT/GO hydrogen bonded with the polymer chains and improved the elasticity of PGEs. The fCNT-PGE demonstrated a slightly lower viscous strain uninform distribution of CNTs in the polymer matrix and the defects formed within. Furthermore, ion diffusion between GO layers was enhanced in fCNT/GO-PGE because fCNT decreased the aggregation of GO sheets and improved the ion channels, increasing the gel ionic conductivity from 41 to 132 mS cm−1. Finally, MnO2-based supercapacitors using PGE, fCNT-PGE, GO-PGE, and fCNT/GO-PGE electrolytes were fabricated with the electrode-specific capacitance measured to be 39.5, 65.5, 77.6, and 83.3 F·g−1, respectively. This research demonstrates the effectiveness of nano carbons as dopants in polymer gel electrolytes for property enhancements.

Green Synthesis of Reduced Graphene Oxide by Using Reducing Sugars

Graphene is a promising candidate for a broad range application in many fields and it has attracted a lot of attention from the researchers due to its unique properties. The involvement of toxic chemicals in synthesisation process is quite worrying as they release toxic gases and cause an explosion. Hence, this research reports a facile and safer method where the improved Hummer’s method was used to synthesize graphene oxide. Chemical reagent reduction method was implemented to synthesize reduced graphene oxide where glucose, fructose and sucrose were used as the reducing agents. The structural and optical properties of GO and rGO was determined by using Fourier Transform Infrared (FTIR) and ultraviolet-visible (UV-Vis) spectrometer. The FTIR analysis of the films showed the existence of a large amount of oxygen-containing functional groups in GO compared to G-rGO, F-rGO and S-rGO. Furthermore, the UV-Vis analysis of GO showed the presence of an absorption peak at 230 nm and also a shoulder at 301 nm. The reduction of GO by sucrose caused a red shift from 230 nm to 260 nm while the reduction of GO by glucose and fructose caused a redshift to 268 nm. By referring to Tauc’s plot method, it was observed that the optical band gaps of GO, G-rGO, F-rGO and S-rGO were 4.26 eV, 3.32 eV, 3.38 eV and 3.66 eV, respectively.

Synergistic antibacterial activity of surfactant free Ag\u2013GO nanocomposites

Graphene oxide–silver (Ag–GO) nanocomposite has emerged as a vital antibacterial agent very recently. In this work, we report a facile one step route of Ag–GO nanocomposite formation excluding the aid of surfactants and reductants and was successfully applied to negative Escherichia Coli (E coli) to investigate antibacterial activity by varying doze concentration. The successful formation of Ag–GO nanocomposite via facile one step route was confirmed using Fourier transform infrared spectroscopy (FTIR) and Raman Spectroscopy. The absorption spectra (peak ~ 300 nm) for GO and the (peak ~ 420 nm) for silver nanoparticles were observed. XRD study confirmed the formation of Ag–GO nanocomposite while atomic force microscopy (AFM) showed crumbled GO sheets decorated with Ag nanoparticles. It was observed that the functional groups of GO facilitated the binding of Ag nanoparticles to GO network and enhanced the antibacterial activity of the nanocomposite.

A highly efficient bifunctional electrocatalyst (ORR/OER) derived from GO functionalized with carbonyl, hydroxyl and epoxy groups for rechargeable zinc–air batteries

A highly efficient bifunctional electrocatalyst, Co–N/S/rGO, was prepared via modifying the surface functional groups of GO, and it showed good application prospects in zinc–air batteries.

Novel determination of Cd and Zn in soil extract by sequential application of bismuth and gallium thin films at a modified screen-printed carbon electrode

This study describes a novel electrochemical technique for the detection of bioavailable cadmium(II) (Cd) and zinc(II) (Zn), in real soil samples. This was made possible by the sequential deposition of bismuth and gallium thin films on modified screen-printed carbon electrodes (SPEs). A range of graphitic modifications were evaluated, and a reduced graphene oxide/graphitic carbon nitride (RGO/g-C3N4) modification proved most suitable. Electrochemical characterisation demonstrated superior stability, attributed to the functional groups of GO, and an increased electron transfer rate, attributed to the intercalated g-C3N4.For voltammetric analysis, cadmium was determined in acetate buffer (pH 4.6) using a bismuth thin film (BiTF). Zn was then determined in the same cell, after adjustment of the pH to 5.1, using a gallium thin film (GaTF). The rationale for two separate thin films is described. Optimisations, such as concentration of bismuth(III), gallium(III), potassium ferrocyanide, pH and deposition potentials, were conducted in the matrix of real samples. The LODs and LOQs were determined in the extracted soil matrix as 0.01 and 0.03 mg kg−1, respectively, for bioavailable Cd and 0.01 and 0.04 mg kg−1, respectively, for bioavailable Zn. Good agreement was observed for Cd and Zn levels in numerous soil samples when compared to the established technique of ICP-OES. This approach opens up the possibility for rapid on-site portable testing of Cd and Zn in real soil samples to determine the probability of Cd uptake by crops.

Arbitrary-shaped reduced graphene oxide aerogels via an unsaturated water vapor reduction

It still remains a challenge to explore facile, economic, and environmental friendly process for the fabrication of graphene aerogels with low density and high purity to meet the various applications. Herein, arbitrary-shaped reduced graphene oxide (rGO) aerogels are prepared by freeze-drying process and followed unsaturated water vapor reduction method staring from GO aqueous suspensions for the first time. Water vapor hydrothermal treatment can decompose all oxygen-containing functional groups in GO and repair GO surface defects effectivly. At higher temperatures (≥175 °C), the carbon in GO may react with water vapor via water-gas shift reaction to form CO, which could also be used as the reductant for the reduction of GO aerogels. The water volume as well as the temperature are key parameters for realizing high reduction degree as well as good shape control of rGO aerogels. Arbitrary shaped rGO aerogels could be prepared by using various molds for freezing GO suspensions. rGO aerogels exhibit a high oil/water separation performance, which could absorb various oils up to 40-55 times of its initial weight with high recyclability. Moreover, the rGO aerogels exhibit typical pressure sensing behavior and excellent energy storage capacitance, which hold great potential applications in flexible pressure sensors and supercapacitors.