Electrochemically Reduced Graphene Oxide Research Articles

Exfoliation of Graphite into Graphene Oxide and Reduction by Plant Extract to Synthesize Graphene

Graphene oxide (GO) is a demand material in industrial field for many applications such as electronic devices, capacitor and sensor. This is due to its unique structures and excellent properties. The GO sheets were exfoliated from graphite rod in electrochemical exfoliation. To reduce GO, an electrochemical reduction of GO using green tea was carried out in this research. The conventional chemical reduction method consumed highly toxic and strongly hazardous chemicals such as hydrazine to reduce GO to reduced GO (RGO). Therefore, a green synthesis method was proposed by using green tea leaves extract as the reducing agent to synthesize RGO. Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) results show that low amount of oxygen-containing functional groups was remained after green tea reduction due to weak reduction capability by green tea. In addition, EDX indicates that oxygen content of GO was decreased from 23.23 to 16.89 Mass% after green tea reduction.

Cytosine-Rich Oligonucleotide and Electrochemically Reduced Graphene Oxide Nanocomposite for Ultrasensitive Electrochemical Ag+ Sensing.

Silver ions (Ag+) are crucial in various fields, but pose environmental and health risks at high concentrations. This study presents a straightforward approach for the ultra-trace detection of Ag+, utilizing a composite of a cytosine-rich oligonucleotide (CRO) and an electrochemically reduced graphene oxide (ERGO). Initially, ERGO was synthesized on a glassy carbon electrode (GCE) through the reduction of graphene oxide (GO) via cyclic voltammetry. A methylene blue-tagged CRO (MB-CRO) was then anchored to the ERGO surface through π-π interactions, resulting in the formation of an MB-CRO-modified ERGO electrode (MB-CRO/ERGO-GCE). The interaction with Ag+ ions induced the formation of silver-mediated C-Ag+-C coordination, prompting the MB-CRO to adopt a hairpin structure. This conformational change led to the desorption of the MB-CRO from the ERGO-GCE, causing a variation in the redox current of the methylene blue associated with the MB-CRO. Electrochemical assays revealed that the sensor exhibits extraordinary sensitivity to Ag+ ions, with a linear detection range from 1 femtomolar (fM) to 100 nanomolars (nM) and a detection limit of 0.83 fM. Moreover, the sensor demonstrated high selectivity for Ag+ ions and several other benefits, including stability, reproducibility, and straightforward fabrication and operational procedures. Additionally, real sample analyses were performed using the modified electrode to detect Ag+ in tap and pond water samples, yielding satisfactory recovery rates.

Direct electrochemical reduction of graphene oxide thin film for aptamer-based selective and highly sensitive detection of matrix metalloproteinase 2

Simple and low-cost biosensing solutions are suitable for point-of-care applications aiming to overcome the gap between scientific concepts and technological production. To compete with sensitivity and selectivity of golden standards, such as liquid chromatography, the functionalization of biosensors is continuously optimized to enhance the signal and improve their performance, often leading to complex chemical assay development. In this research, the efforts are made on optimizing the methodology for electrochemical reduction of graphene oxide to produce thin film-modified gold electrodes. Under the employed specific conditions, 20 cycles of cyclic voltammetry (CV) are shown to be optimal for superior electrical activation of graphene oxide into electrochemically reduced graphene oxide (ERGO). This platform is further used to develop a matrix metalloproteinase 2 (MMP-2) biosensor, where specific anti-MMP2 aptamers are utilized as a biorecognition element. MMP-2 is a protein which is typically overexpressed in tumor tissues, with important roles in tumor invasion, metastasis as well as in tumor angiogenesis. Based on impedimetric measurements, we were able to detect as low as 3.32 pg mL−1 of MMP-2 in PBS with a dynamic range of 10 pg mL−1 – 10 ng mL−1. Further experiments with real blood samples revealed a promising potential of the developed sensor for direct measurement of MMP-2 in complex media. High specificity of detection is demonstrated – even to the closely related enzyme MMP-9. Finally, the potential of reuse was demonstrated by signal restoration after experimental detection of MMP-2.

Iron/Iron(III) Oxide Decorated on Electrochemically Reduced Graphene Oxide: a Novel One-Step Electrosynthesis and a Fabrication of an Electrochemical Ascorbic Acid Sensor

Considering on required detection time and sensitivity, electrochemical method is an excellent candidate for ascorbic acid (AA) sensing. We propose using the synergistic effects of iron(0)/iron(III) oxide decorated on the electrochemically reduced graphene oxide (ERGO/Fe-Fe2O3) modified Pt microelectrode as an electrochemical AA sensor using cyclic voltammetry (CV) technique. Herein, ERGO/Fe-Fe2O3 was directly fabricated on the Pt microelectrode using a novel one-step electrosynthesis. Fe-Fe2O3 acts as an oxidized-nanozyme with works as redox centers on the electrode for oxidation of AA. Fe-Fe2O3 nanozymes are immobilized on electrochemically reduced graphene oxide (ERGO), which supports a large electroactive and excellent electrically conductive surface for electron-transfer during electrochemical oxidation of AA. The developed electrochemical sensor allowed for sensing AA in medical samples with high sensitivity in concentration range from 0.05 to 10.00 mM and a limit of detection (LOD) of 5.93 μM.

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.

A novel electrochemical strategy to detect hydrogen peroxide by utilizing peroxidase-mimicking activity of cerium oxide/graphene oxide nanocomposites

We herein describe a novel electrochemical strategy to detect hydrogen peroxide (H2O2) by utilizing the peroxidase-mimicking activity of cerium oxide nanoparticles (CeO2 NP) and reduced graphene oxide (rGO). Particularly, CeO2 NP/rGO nanocomposites were deposited on the commercial electrode by a very convenient and direct electrochemical reduction of graphene oxide. Due to the peroxidase-mimicking activity of CeO2 NP and the outstanding electrochemical properties of reduced graphene oxide, the reduction current of H2O2 was greatly enhanced. Based on this strategy, we reliably determined H2O2 down to 1.67 μM with excellent specificity and further validated its practical capabilities by robustly detecting H2O2 present in heterogeneous human serum samples. We believe that this work could serve as a new facile platform for H2O2 detection.

Triple multivalent aptamers within DNA tetrahedron on reduced graphene oxide electrode: Unlocking enhanced sensitivity and accelerated reactions in electrochemical sensing

DNA nanostructures are emerging as promising biosensing platforms due to their programmability, predictable assembly, and compatibility with aptamers for enhanced selectivity. This study focuses on a triple-multivalent aptamer (tApt) complex immobilized on a tetrahedral DNA nanostructure (TDN) and integrated with an electrochemically reduced graphene oxide (ERGO) electrode for highly sensitive mercury ion (Hg2+) detection. Compared to a linear multivalent aptamer-modified electrode (S2/ERGO-GCE), the 3D tApt/ERGO-GCE aptasensor exhibits superior sensitivity, signal amplification, and reaction kinetics. The tApt/ERGO-GCE sensor achieves an exceptional limit of detection (LOD) of 4.1 zM, surpassing the LOD of 0.71 fM for S2/ERGO-GCE. Additionally, the tApt/ERGO-GCE sensor demonstrates faster response times, with a half-saturation time (T1/2) of 6 minutes compared to 17 minutes for S2/ERGO/GCE. The 3D tApt aptamer's superior performance is attributed to its tetrahedral DNA structure integrated on ERGO, providing multiple aptamer binding sites, facilitating oriented immobilization on the electrode surface, and enhancing analyte capture and concentration. In contrast, the linear S2 aptamers lack rigidity, resulting in a disordered orientation on the electrode surface, hindering efficient Hg2+ binding and reducing target molecule binding efficiency. This study underscores the potential of triple-multivalent aptamer-based nanostructures for ultrasensitive and rapid biosensing applications. The tApt/ERGO-GCE aptasensor's exceptional sensitivity, signal amplification, and reaction kinetics make it a promising tool for Hg2+ detection and other biosensing applications.

The impact of interdigitated metal electrode on properties and performance of electrochemically reduced graphene oxide (ErGO) UV photodetector

The impact of interdigitated metal electrode on properties and performance of electrochemically reduced graphene oxide (ErGO) UV photodetector

Enhancement of Electrochemically Reduced Graphene Oxide (ErGO) UV Photo Detector Performance via Direct One-Step Electrode Deposition Technique

Recently, photodetectors have garnered significant attention owing to their broad spectrum of applications across fields such as the biomedical, industrial, agricultural, and telecommunications sectors. This research focuses on the development of a UV photodetector based on electrochemically reduced graphene oxide (ErGO) and incorporates reduced graphene oxide (rGO) thin films on interdigitated Au electrodes. The rGO thin films were synthesized using the direct one-step deposition method, maintaining a constant water bath temperature of 40 °C, and a consistent GO concentration of 0.15 g, while varying the pH levels within the range of pH 8 to pH 10. The investigation primarily concentrated on assessing the surface morphological, structural, and electrical properties of the rGO thin films by altering the pH level when exposed to 365 nm ultraviolet (UV) irradiation. The significant parameters for evaluating photodetector performance, including photosensitivity, stability, repeatability, response time, and recovery time. To achieve this, advanced techniques such as field-emission scanning electron microscopy (FESEM), Raman spectroscopy, and current-time measurement are employed. As a finding, the fabricated UV PD of rGO-Au at pH 9 achieved the photosensitivity 96.5% with the stability that was 30 times greater than rGO-Au (pH 10) and superior repeatability as well as rapid switching rate as compared to pH 8 and pH 10 with 0.6 V bias. This implies that rGO-Au prepared at pH 9 is a suitable material for application in UV detection.

Synergistic coupling of reduced graphene oxide with Ni0.85Se for highly active bifunctional electrocatalyst for water splitting

Electrochemical water splitting can provide eco-friendly fuel. Nevertheless, this method requires efficient bifunctional electrocatalysts. In this study, a bifunctional electrocatalyst was synthesized by coating Ni0.85Se and hydrothermally-reduced graphene oxide on nickel foam (NF) using two-step electrodeposition. Moreover, graphene oxide was reduced through hydrothermal means prior to the pulse reverse electrodeposition. As confirmed by FT-IR, hydrothermally and electrochemically reduced graphene oxide on NF (HERGO) reveals a higher reduction degree in comparison to electrochemically-reduced graphene oxide on NF (ERGO). Ni0.85Se covered HERGO through the on-off cathodic pulse electrodeposition. Therefore, excellent electrocatalytic activity was obtained using the synergetic effect of RGO and Ni0.85Se. The ECSA values of 431 and 3500 cm2 were attained through coating HERGO and Ni0.85Se/HERGO on bare NF, respectively. The Ni0.85Se/HERGO revealed Ƞ10 of 67 and 230 mV for HER and OER, respectively. For overall water splitting, the Ni0.85Se/HERGO ǁ Ni0.85Se/HERGO device requaired 1.533 V at 10 mA/cm2.

Electrochemically Reduced Graphene Oxide Supported Palladium-Cobalt Alloy Nanoparticles as Highly Efficient Electrocatalyst for Oxygen Reduction Reaction

Pd-Co alloy nanoparticles were synthesized on electrochemically reduced graphene oxide (ErGO) for electrocatalytic oxygen reduction reaction (ORR) in alkaline media. The morphological structure, chemical composition, and crystallinity of the afforded ErGO/Pd-Co catalyst were examined by various techniques, including transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analysis. The Pd-Co alloy nanoparticles were evenly distributed on the ErGO sheet and had a narrow size distribution, with an average particle size of 4.25 nm. The ORR activity of the as-prepared ErGO/Pd-Co alloy catalyst was evaluated by cyclic voltammetry, linear sweep voltammetry, rotating disk electrode, and rotating ring disk electrode techniques in an alkaline electrolyte. The ErGO/Pd-Co catalyst exhibits a very high electrocatalytic activity in ORR with the mass activity more than 2.0 times of the commercial 20% Pt/C due to the synergistic catalytic effect of both ErGO and Pd-Co nanoparticles. Electrocatalytic kinetics investigation shows that, the ORR on the ErGO/Pd-Co catalyst proceeds through four electrons transferred mechanism with negligible amount of peroxide species. Moreover, the ErGO/Pd-Co shows an excellent methanol tolerance than the commercial 20% Pt/C.

Design of nanohybrids based on layered double hydroxides and electrochemically reduced graphene oxide for energy applications

An innovative electrosynthesis method recently developed by our research group for the composite Ni/Al layered double hydroxide (LDH) intercalated with electrochemically reduced graphene oxide (ERGO) has been successfully applied to the deposition of Co/Al LDH ERGO on Grafoil sheets, demonstrating the high versatility of the procedure. Four materials have been electrosynthesized and characterized structurally and morphologically: Ni/Al LDH, Ni/Al LDH ERGO, Co/Al LDH, and Co/Al LDH ERGO. A deep investigation of their electrical and electrochemical properties in terms of Faradaic processes involving the redox active metal centers has been carried out. The effect of the presence of ERGO in the composite materials has been studied, highlighting an improvement of the electrical conductivity and the Faradaic process kinetics only for the Ni based LDH. The Co/Al LDH ERGO modified Grafoil was investigated as positive electrode in an asymmetric supercapacitor in solution and its performance compared with the one exhibited by the pure LDH. Also in such a case, the intercalation of ERGO inside the Co/Al LDH has not affected significantly its properties in terms of capacitance, but only has shown a positive effect on the material stability.

Ultrasensitive and selective electrochemical sensor for nanomolar dopamine determination based on MnS/Co3S4 hybrids embedded on electrochemically reduced graphene oxide

An ultrasensitive and selective electrochemical sensor has been constructed for the quantitative assay of dopamine (DA) based on hollow tubular manganese-cobalt sulfide (MnS/Co3S4) hybrids embedded on electrochemically reduced graphene oxide (ErGO). The MnS/Co3S4 heterostructures were created by two-step ion exchange method, of which Co9S8 with hollow tubular structures was fabricated by solvothermal method using the self-made cobalt chloride carbonate hydroxide (CO(CO3)0.35Cl0.20(OH)1.10) as precursor and sodium disulfide monohydrate as sulfur source and manganese chloride as manganese source. The MnS/Co3S4-ErGO/GCE could exhibit strong catalytic ability for the redox reaction of DA. Under the optimal conditions, the developed sensor exhibits a wide linear response for DA ranging from 6.0 nM to 20.0 μM by second-order derivative linear sweep voltammetry (SDLSV), with a detection limit of 2.0 nM. In addition, the developed method exhibited high sensitivity and selectivity, good reproducibility and low-cost. It is a very promising analytical method for the determination of DA in pharmaceutical and biological samples.

Development of recycled and miniaturized electroanalytical sensor: Probing isoniazid determination in environmental water matrices

Surface water pollution has become relevant because growing population and intense industrial activities. Thus, to protect the environment from contamination, recently the electroanalytical sensors that require small sample volume and easy preparation have shown a prominent performance for pharmaceuticals monitoring. For this purpose, a miniaturized electrochemical platform was developed based on recycling obsolete computer integrated circuits (microchips), fitting with the ideals of green chemistry and circular economy. The gold microelectrodes array (Au-μEA) was easily exposed by polishing the device surface and then characterized by optical microscopy, scanning electron microscopy and cyclic voltammetry. To enhance the analytical performance for isoniazid detection, the Au-μEA was modified with electrochemically reduced graphene oxide (ERGO). The developed sensor presented a linear range between 5 and 100 μmol L−1 and a limit of detection of 1.38 μmol L−1 demonstrating a reliable performance. Looking to its environmental application, the ERGO/Au-μEA sensor was used for isoniazid quantification in lagoon, river, tap water and synthetic effluent spiked samples with recovery values between 92.5 and 108.4%. Thus, this research field opens up new possibilities in global water-related issues contributing with innovative sustainable solutions.

Ultrasensitive Electrochemical Platform for Dopamine Detection Based on CoNi-MOF@ERGO Composite.

An electrochemical sensor applied for dopamine (DA) detection was constructed. An easy static way was used to synthesize bimetallic CoNi-MOF. Next, it was mixed with graphene oxide (GO) under ultrasound to get a uniform suspension. Subsequently, the solution was coated on the glassy carbon electrode (GCE) to form CoNi-MOF@ERGO/GCE by the electrochemical reduction method. The interaction between CoNi-MOF and electrochemically reduced graphene oxide (ERGO) enhances the electrocatalytic performance for DA detection. CoNi-MOF@ERGO/GCE has a wider linear range (0.1-400 μM) and a lower detection limit (0.086 μM) under optimum conditions. Furthermore, it has been applied to test DA in human serum samples. The results reveal that the DA sensor shows excellent performance, which will provide a novel idea for more sensitive and quicker DA detection.

Nanocomposite of Electrochemically Reduced Graphene Oxide and Poly (p‐aminobenzenesulfonic acid) Incorporated with Ni (II) Ions as an Electrocatalyst for the Oxidation of Methanol

AbstractA new nanocomposite containing Ni(II) ions, electrochemically reduced graphene oxide (ERGO) and poly (p‐aminobenzenesulfonic acid) (Pp‐ABSA) on pencil graphite electrode (PGE) was prepared using electrochemical deposition coupled with self‐assembly accumulation method and characterized with different techniques. The electrochemical behavior and electrocatalytic activity of modified PGEs were investigated. The Ni/Pp‐ABSA/ERGO/PGE showed a unique electrocatalytic oxidation through an Electrochemical‐Chemical (EC’) pathway for methanol in alkaline media (Jpf=7.04 mA cm−2 and Eonest=0.38 V) compared to Ni/PGE, Ni/Pp‐ABSA/PGE and Ni/ERGO/PGE. The obtained results showed that the self‐assembled incorporation of Ni(II) ions in Pp‐ABSA/ERGO film prepared on PGE surface produced a stable modifier with high electrocatalytic activity towards methanol oxidation. In conclusion, the introduced method for the preparation of Pp‐ABSA/ERGO‐based nanocomposites can open a new, cheap and simple way to design a high‐performance electrocatalyst for direct methanol fuel cell systems.

Classification-Based Evaluation of Multi-Ingredient Dish Using Graphene-Modified Interdigital Electrodes.

A taste sensor with global selectivity can be used to discriminate taste of foods and provide evaluations. Interfaces that could interact with broad food ingredients are beneficial for data collection. Here, we prepared electrochemically reduced graphene oxide (ERGO)-modified interdigital electrodes. The interfaces of modified electrodes showed good sensitivity towards cooking condiments in mixed multi-ingredients solutions under electrochemical impedance spectroscopy (EIS). A database of EIS of cooking condiments was established. Based on the principal component analysis (PCA), subsets of three taste dimensions were classified, which could distinguish an unknown dish from a standard dish. Further, we demonstrated the effectiveness of the electrodes on a typical dish of scrambled eggs with tomato. Our kind of electronic tongue did not measure the quantitation of each ingredient, instead relying on the database and classification algorithm. This method is facile and offers a universal approach to simultaneously identifying multiple ingredients.

Comparison of Electrochemical Reduction of GO with LiCl and KOH by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS).

Comparison of Electrochemical Reduction of GO with LiCl and KOH by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS).

Electrochemical Fine-Tuning of the Chemoresponsiveness of Langmuir-Blodgett Graphene Oxide Films.

Graphene oxide has been widely deployed in electrical sensors for monitoring physical, chemical, and biological processes. The presence of abundant oxygen functional groups makes it an ideal substrate for integrating biological functional units to assemblies. However, the introduction of this type of defects on the surface of graphene has a deleterious effect on its electrical properties. Therefore, adjusting the surface chemistry of graphene oxide is of utmost relevance for addressing the immobilization of biomolecules, while preserving its electrochemical integrity. Herein, we describe the direct immobilization of glucose oxidase onto graphene oxide-based electrodes prepared by Langmuir-Blodgett assembly. Electrochemical reduction of graphene oxide allowed to control its surface chemistry and, by this, regulate the nature and density of binding sites for the enzyme and the overall responsiveness of the Langmuir-Blodgett biofilm. X-ray photoelectron spectroscopy, surface plasmon resonance, and electrochemical measurements were used to characterize the compositional and functional features of these biointerfaces. Covalent binding between amine groups on glucose oxidase and epoxy and carbonyl groups on the surface of graphene oxide was successfully used to build up stable and active enzymatic assemblies. This approach constitutes a simple, quick, and efficient route to locally address functional proteins at interfaces without the need for additives or complex modifiers to direct the adsorption process.

In-situ electrochemical synthesis of heteroatoms-doped reduced graphene oxide toward nonradical degradation of tetracycline

Nonradical-based advanced oxidation processes (AOPs) catalyzed by defective carbonaceous materials have exhibited great superiorities in trace antibiotics removal from natural water matrices. However, the complicated, extensive and highly-energy consumed synthesis methods are seriously hindering its development and application. Herein an in-situ electrochemical synthesis technology was developed and N/B/F-codoped RGO was assembled on the Ti foam effectively by using ionic liquid (IL) as the heteroatoms parents. Other benefits of the IL including anti-RGO agglomeration, suppressing hydrolysis side reaction and reducing internal resistance were also demonstrated. Based on the diverse substrates exploration and comprehensive characterizations, adsorption and desolvation of the water molecules around IL-GO was found the two critical procedures for GO reduction and heteroatoms-doping. Hydrophilicity and porosity are the two essential properties for substrate selection. The solvent substitute experiments indicated electrochemical reduction of GO is a proton-mediated electron transfer reaction and the protons come from the solvent. Remarkable heteroatoms content was obtained from −1.0 V ∼ -1.2 V within 30 min under normal temperature and pressure. The degradation performance of N/B/F-codoped RGO was examined in an electrochemical system without any chemical additive. 93.0 % of trace tetracycline (5 mg L-1) was removed at −0.6 V within 60 min and the corresponding TOC removal efficiency was 40 %. Electron transfer efficiency can be even improved in the natural water matrices. The degradation mechanism investigation suggested that N/B/F-codoped RGO is able to simultaneously catalyze two nonradical pathways including electron transfer and singlet-dominated AOP. This work provides a highly effective, green and low-cost nonradical-based AOP technology for controlling antibiotics pollution in the environmental water matrices.