Electrochemical Exfoliation Research Articles

Prototyping a wearable and stretchable graphene-on-PDMS sensor for strain detection on human body physiological and joint movements.

In the era of wearable electronic devices, which are quite popular nowadays, our research is focused on flexible as well as stretchable strain sensors, which are gaining humongous popularity because of recent advances in nanocomposites and their microstructures. Sensors that are stretchable and flexible based on graphene can be a prospective 'gateway' over the considerable biomedical speciality. The scientific community still faces a great problem in developing versatile and user-friendly graphene-based wearable strain sensors that satisfy the prerequisites of susceptible, ample range of sensing, and recoverable structural deformations. In this paper, we report the fabrication, development, detailed experimental analysis and electronic interfacing of a robust but simple PDMS/graphene/PDMS (PGP) multilayer strain sensor by drop casting conductive graphene ink as the sensing material onto a PDMS substrate. Electrochemical exfoliation of graphite leads to the production of abundant, fast and economical graphene. The PGP sensor selective to strain has a broad strain range of ⁓60%, with a maximum gauge factor of 850, detection of human physiological motion and personalized health monitoring, and the versatility to detect stretching with great sensitivity, recovery and repeatability. Additionally, recoverable structural deformation is demonstrated by the PGP strain sensors, and the sensor response is quite rapid for various ranges of frequency disturbances. The structural designation of graphene's overlap and crack structure is responsible for the resistance variations that give rise to the remarkable strain detection properties of this sensor. The comprehensive detection of resistance change resulting from different human body joints and physiological movements demonstrates that the PGP strain sensor is an effective choice for advanced biomedical and therapeutic electronic device utility.

High Potential Electrochemical Synthesis of Thermally Reduced Graphene Nanomaterial

In this study, we provide electrochemical techniques for synthesizing thermally reduced graphene nanomaterial that have high potential, low defects, cost-effectiveness, and ecological sustainability. The electrochemical exfoliation is carried out by employing a 195 W DC (voltage = 60[Formula: see text]V and current = 3.25 A) power source at a maximum electrolyte temperature of about 92.5∘C within the aqueous suspension of 2[Formula: see text]M of sulfuric acid (H2SO[Formula: see text]. Thereafter, the synthesized nanomaterial was treated in the weak piranha [combination of sulfuric acid and hydrogen peroxide (H2O[Formula: see text]] solution using an electrochemical technique inside the water bath sonicator at 80∘C. X-ray diffraction (XRD) analysis shows the peak of diffraction to the (002) plane of the reduced graphene oxide (RGO) samples emerges at around 2[Formula: see text] and 26.56∘ with an interplanar distance of 3.40 Å and 3.54 Å. According to the XRD data, after the high-temperature thermal reduction phase, the structure of the crystals and interplanar separation were recovered. The size of the crystallite of RGO produced under H2SO4 conditions was discovered to be greater than the crystallite size of graphene oxide produced under piranha solution conditions. The Raman analysis results show that the degree of disorder of the graphene synthesized within the H2O2 was higher than in comparison to the graphene synthesized in H2SO4. Field emission scanning electron microscopy (FE-SEM) results show that graphene synthesized in the presence of H2O2 has a thin and porous microstructure in comparison to H2SO4 with no significant effect on the presence of the availability of the C/O ratio. The atomic force microscopy (AFM) analysis indicates that the surface roughness of the graphene synthesized in the H2O2 was higher than that of the H2SO4. The Fourier transform infrared spectroscopy (FT-IR spectroscopy) analytical results show that the majority of the functional groups have been eliminated within the samples.

Morphological and Thermal Characterization of Low-Cost Graphene Produced by Electrochemical Exfoliation Method

The low-cost and mass production of graphene has gained importance in recent years. The electrochemical exfoliation method, one of the graphene production methods, is an efficient technique used to obtain low-cost-effective and large quantities of graphene nanosheets. Exfoliation parameters affect the properties of exfoliated graphene nanosheets. In this study, graphene production is fabricated by the method of exfoliation using electrolyte and voltage parameters. For this, a pen tip was used instead of pure platinum, which is very expensive, at the cathode. The structural research was done by X-ray diffraction spectroscopy (XRD), Raman spectroscopy and Fourier Transform Infrared Spectrometer (F-TIR). Morphological analyses were carried out by Scanning Electron Microscopy (SEM). The number of layers and crystallite of graphene layers were estimated. The obtained results were compared with the results of the other similar studies. Analysis results show that low-cost multilayer graphene can be produced by the electrochemical exfoliation method with the electrical parameters.

Growth and physical-chemical characterization of manganese oxide and graphene-manganese oxide films for potential applications in energy store devices

The need for progress in the development of energy supply devices such as batteries and large capacitors has led to the improvement and innovation of these devices so that they can store energy efficiently, and additionally, they must be small, light, with low production costs, and friendly to the environment. For these reasons, in this investigation results of the characterization of physical and chemical behaviors of graphene-manganese oxide and copper and manganese oxide-copper systems are studied. The graphene was synthesized through the electrochemical exfoliation technique and deposited as a film on common glass and silicon substrates via the spray technique, and over this film, Mn2O3 films were deposited through spin coating. The Raman results showed the presence of peaks D and G, located at 1534 and 1597 cm−1, respectively. XPS analysis demonstrated that the graphene is made up of three layers. TEM studies determined that the graphene is polycrystalline, and XRD established the manganese oxide coatings’ growth along the (222) and (440) planes of Mn2O3. The optical behavior indicated that the absorbance of the graphene-Mn2O3 system decreases the energy gap in 0.8 eV concerning Mn2O3 films. The voltage-current measurements suggest that the density current in the discharge process of the Mn2O3–Cu electrode system was improved approximately 3-fold with the graphene-Mn2O3–Cu electrode system. The obtained results conclude that the addition of graphene to manganese oxide coatings increases their electrochemical performance, so graphene-manganese oxide could be used in energy storage devices.

Electrochemical Exfoliation and Growth of Nickel–Cobalt Layered Double Hydroxides@Black Phosphorus Hetero‐Nanostructure Textiles for Robust Foldable Supercapacitors

AbstractAdvanced innovation of flexible electrode with adequate redox activity and stably mechanical endurance that promotes charges kinetic migration and faradaic storage is pivotal for textile‐based supercapacitors (T‐SCs). Herein, this study reports a high‐performance T‐SCs electrode based on nickel–cobalt layered double hydroxides@black phosphorus (NiCo‐LDHs@BP) on a conductive silk (c‐silk) textile (NiCo‐LDHs@BP/c‐silk). Under negative voltage‐induced electrochemical exfoliation, the Ni2+ and Co2+ are embedded into bulk BP framework to form exfoliated BP nanosheets, and the NiCo‐LDHs are in situ grown within the BP networks, generating 3D NiCo‐LDHs@BP hetero‐nanostructure. Significantly, the NiCo‐LDHs@BP exhibits a large space‐charge area, enhanced adsorption energy for OH− and accelerated charges transfer/storage as confirmed using density functional theory calculations. Additionally, the T‐SCs electrode is fabricated by loading the blended NiCo‐LDHs@BP, sericin, and carbon nanotubes on fibroin textile via a silk reconstruction strategy, producing large area production, superior mechanical flexibility, and impressive electrochemical performance. The resultant NiCo‐LDHs@BP/c‐silk electrode exhibits large specific capacitance of 1291.3 F g−1 and considerable rate capacity in 1 M KOH electrolyte. Furthermore, the flexible solid‐state asymmetric T‐SCs deliver high specific areal energy density of 279.6 µWh cm−2 and robust folding capability (85.6% capacitance retention after 5000 folding cycles), which successfully power wearable watch and heart rate meter devices.

Knot Architecture for Biocompatible and Semiconducting 2D Electronic Fiber Transistors.

Wearable devices have generally been rigid due to their reliance on silicon-based technologies, while future wearables will utilize flexible components for example transistors within microprocessors to manage data. Two-dimensional (2D) semiconducting flakes have yet to be investigated in fiber transistors but can offer a route toward high-mobility, biocompatible, and flexible fiber-based devices. Here, the electrochemical exfoliation of semiconducting 2D flakes of tungsten diselenide (WSe2) and molybdenum disulfide (MoS2) is shown to achieve homogeneous coatings onto the surface of polyester fibers. The high aspect ratio (>100) of the flake yields aligned and conformal flake-to-flake junctions on polyester fibers enabling transistors with mobilities μ ≈1 cm2 V-1 s-1 and a current on/off ratio, Ion/Ioff ≈102-104. Furthermore, the cytotoxic effects of the MoS2 and WSe2 flakes with human keratinocyte cells are investigated and found to be biocompatible. As an additional step, a unique transistor 'knot' architecture is created by leveraging the fiber diameter to establish the length of the transistor channel, facilitating a route to scale down transistor channel dimensions (≈100 µm) and utilize it to make a MoS2 fiber transistor with a human hair that achieves mobilities as high as μ ≈15 cm2 V-1 s-1.

Synthesis and Characterization of Graphene Nanoplatelets Fabricated by Electrochemical Exfoliation Method for Conductive Adhesive

Synthesis and Characterization of Graphene Nanoplatelets Fabricated by Electrochemical Exfoliation Method for Conductive Adhesive

Synthesis of Graphene from Pencils Graphite Via Electrochemical Exfoliation Method as a Cu-Foil Coating on the Anode-Free Lithium-Ion Battery

The Anode-free Li-ion Battery (AFLB) is an alternative to a new Li-ion battery model that offers high energy density at the same battery size as conventional models. Uncontrolled dendrite growth inactive the lithium deposition, resulting in decreased specific capacity, shortened lifecycle, and reduced coulombic efficiency. This work reported the utilization of graphene derived from pencil graphite for coating Cu foil as a current collector in AFLBs, to mitigate the formation of lithium dendrites and enhance battery capacity. The graphene-coated Cu foil exhibits a specific capacity of 143 mAh/g, representing a 20 mAh/g increase compared to batteries lacking a graphene coating. The coulombic efficiency of the battery with graphene coating in the charging and discharging process for three cycles is 84.53% in the 1<sup>st</sup> cycle, 101.44% in the 2<sup>nd</sup> cycle, and 98.58% in the 3<sup>rd</sup> cycle.

Harnessing Graphene-Modified Electrode Sensitivity for Enhanced Ciprofloxacin Detection.

Increased evidence has documented a direct association between Ciprofloxacin (CFX) intake and significant disruption to the normal functions of connective tissues, leading to severe health conditions (such as tendonitis, tendon rupture and retinal detachment). Additionally, CFX is recognized as a potential emerging pollutant, as it seems to impact both animal and human food chains, resulting in severe health implications. Consequently, there is a compelling need for the precise, swift and selective detection of this fluoroquinolone-class antibiotic. Herein, we present a novel graphene-based electrochemical sensor designed for Ciprofloxacin (CFX) detection and discuss its practical utility. The graphene material was synthesized using a relatively straightforward and cost-effective approach involving the electrochemical exfoliation of graphite, through a pulsing current, in 0.05 M sodium sulphate (Na2SO4), 0.05 M boric acid (H3BO3) and 0.05 M sodium chloride (NaCl) solution. The resulting material underwent systematic characterization using scanning electron microscopy/energy dispersive X-ray analysis, X-ray powder diffraction and Raman spectroscopy. Subsequently, it was employed in the fabrication of modified glassy carbon surfaces (EGr/GC). Linear Sweep Voltammetry studies revealed that CFX experiences an irreversible oxidation process on the sensor surface at approximately 1.05 V. Under optimal conditions, the limit of quantification was found to be 0.33 × 10-8 M, with a corresponding limit of detection of 0.1 × 10-8 M. Additionally, the developed sensor's practical suitability was assessed using commercially available pharmaceutical products.

Synthesis of highly efficient ternary phase graphene/Bi/SnO2 photocatalyst for degradation of organic dye pollutants

In this work, graphene nanosheets (GNs) are prepared from graphite rods obtained from waste dry-cell batteries using the electrochemical exfoliation (ECE) method. Then GNs used as a matrix to modify tin oxide (SnO2) and Bismuth (Bi) nanoparticles to prepare a binary phase SnO2@G and ternary-phase Bi@SnO2@G nanocomposite materials by wet-chemical method and used as a photocatalysts for degradation of organic dye pollutants. XRD diffraction pattern clearly confirmed the presence of tetragonal crystal system of SnO2 which was maintaining its structure in SnO2@G and G/Bi/SnO2. The stretching and bending vibrations of the functional groups were analyzed using FTIR analysis. FESEM images demonstrated the surface morphology and the texture of the as synthesized sample. Raman Spectroscopic investigation was carried out to confirm the in-plane blending of SnO2 and graphene inside the composite matrix. The as-prepared ternary-phase Bi@SnO2@G-based photocatalyst showed high degradation efficiency of 99.6% and 94.5% for direct blue (DB) and methyl blue (MB) dyes, respectively, under visible light irradiation by (i) minimizing the hole and electron recombination, (ii) providing a high surface area, and (iii) reducing the band gap energy. This study provides an effective, low-cost, and smart approach for producing GNs on a wide scale from battery waste along with nanohybrid composites with high photocatalytic efficiency.

The influence of interface products on the mechanical and electrical properties of graphene aluminum composites

Graphene has been identified as an efficient filler to increase the strength and conductivity of aluminum but the reaction between aluminum and graphene at elevated temperature is inevitable. In this research, diverse interfacial products between aluminum and graphene were generated by modulating the sintering temperature, and their influences on the mechanical and electrical characteristics of graphene-aluminum composites were examined. Copper encapsulation on graphene has been utilized to isolate graphene from contacting aluminum directly as well as to doping graphene for conduction purposes. The synthesis of copper-coated graphene-reinforced aluminum composites involved several steps, including electrochemical exfoliation, electroless chemical deposition, mechanical ball milling, and high-pressure sintering. The results demonstrate that the formation of a solid solution between copper nanoparticles and aluminum promotes strong interfacial bonding with graphene, leading to a 22.76 % improvement in the conductivity of the composite compared to the pristine aluminum matrix. Additionally, by minimizing the formation of aluminum carbide, the addition of graphene results in a tensile strength of 404 MPa for the composite material, representing a significant 88.8 % increase over the aluminum matrix.

Scalable fabrication of two-dimensional Bi2Se3 for high-performance supercapacitors

Although having an advantageous charge–discharge rate, supercapacitors, in terms of energy density, are still dwarfed by their battery counterparts, thereby hindering their industrial use. Two-dimensional (2D) Bi2Se3, which is characterized by high electrical conductivity, possesses a large theoretical specific capacity that has not been experimentally realized. In this study, we employed scalable electrochemical exfoliation to fabricate high-quality Bi2Se3 nanosheets with a yield of over 95 %. These nanosheets were then applied as anode materials with the hitherto highest specific capacitance of 662.5 F/g at 1A/g to assemble asymmetric supercapacitors (ASCs) of Bi2Se3//NiCo2S4. The supercapacitors demonstrated an extraordinary energy density of 48 Wh/kg at a power density of 800 W/kg and efficiently drove devices such as perovskite-LEDs. This study reveals the huge potential of 2D Bi2Se3 as an efficient supercapacitor electrode via a primary Faradaic pseudocapacitive storage mechanism. The scalable production of this material is expected to stimulate its widespread and practical use.

Covalently Bonded Ni Sites in Black Phosphorene with Electron Redistribution for Efficient Metal-Lightweighted Water Electrolysis

HighlightsBlack phosphorene (BP) was functionalized by the ionized Ni through an in situ electrochemical exfoliation method.Just 1.5 wt% Ni-functionalized BP can stably deliver the efficient alkaline H2/O2 evolution electrocatalysis.Optimized intermediate chemisorption is enabled by Ni–P covalent bonding and electron redistributed surface.

Exploiting Carbon Quantum Dots Synthesized by Electrochemical Exfoliation for Flexible Resistance Switching

Exploiting Carbon Quantum Dots Synthesized by Electrochemical Exfoliation for Flexible Resistance Switching

Preliminary study of exfoliated graphite (EG) produced by electrochemical exfoliation and EG-TiO2 composite

In this research, Exfoliated Graphite (EG) materials have been synthesized using the electrochemical exfoliation method. The starting materials are graphite sheets, before the exfoliation process, a simple pre-treatment was carried out, by immersing the graphite sheet in a mixture solution of sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) with a ratio of 95:5 to widen the interlayer distance in graphite sheets for the optimum electrochemical exfoliation process. This study used ammonium sulfate solution (NH4)2SO4 as an electrolyte with a concentration 0.25 M. The obtained EG materials are then composited with TiO2 to increase the resulting energy density of the materials. The in-situ sol-gel method was used to synthesize the EG-TiO2 composite assisted by microwave irradiation. The resulting materials were characterized using X-ray diffraction (XRD), Fourier Transform infrared (FTIR), and LCR meter. Based on the XRD results, the EG-TiO2 composite showed an amorphous structure with an average crystallite size of 24.9 - 49.9 nm. It also shows that the XRD pattern of the EG-TiO2 composite has a lower peak intensity than the EG material. The FTIR result shows that the functional group of the rGO-TiO2 composite has a combination of Ti-O-Ti and Ti-O-C vibrations, which indicates the chemical interaction of TiO2 with EGs.

Scalable Production of Highly Conductive 2D NbSe2 Monolayers with Superior Electromagnetic Interference Shielding Performance.

Thin, flexible, and electrically conductive films are in demand for electromagnetic interference (EMI) shielding. Two-dimensional NbSe2 monolayers have an electrical conductivity comparable to those of metals (106-107 S m-1) but are challenging for high-quality and scalable production. Here, we show that electrochemical exfoliation of flake NbSe2 powder produces monolayers on a large scale (tens of grams), at a high yield (>75%, monolayer), and with a large average lateral size (>20 μm). The as-exfoliated NbSe2 monolayer flakes are easily dispersed in diverse organic solvents and solution-processed into various macroscopic structures (e.g., free-standing films, coatings, patterns, etc.). Thermal annealing of the free-standing NbSe2 films reduces the interlayer distance of restacked NbSe2 from 1.18 to 0.65 nm and consequently enhances the electrical conductivity to 1.16 × 106 S m-1, which is superior to those of MXenes and reduced graphene oxide. The optimized NbSe2 film shows an EMI shielding effectiveness (SE) of 65 dB at a thickness of 5 μm (>110 dB for a 48-μm-thick film), among the highest in materials of similar thicknesses. Moreover, a laminate of two layers of the NbSe2 film (2 μm thick) with an insulating interlayer shows a high SE of 85 dB, surpassing that of the 20-μm-thick NbSe2 film (83 dB). A two-layer theoretical model is proposed, and it agrees with the experimental EMI SE of the laminated NbSe2 films. The ability to produce NbSe2 monolayers on a tens of grams scale will enable their diverse applications beyond EMI shielding.

Ultra-sensitive electrochemical detection of glutamate based on reduced graphene oxide/Ni foam nanocomposite film fabricated via electrochemical exfoliation technique using waste batteries graphite rods

Glutamate (Glut) is the most abundant excitatory neurotransmitter in our brain and central nervous system (CNS) that is essential for the proper functioning of the brain. The uneven concentration of glutamate causes cell’s overstimulation which leads to many severe diseases, including brain cancer, and brain cell damage. Further, the overexcitation of neuronal cells which is involved in the neurotoxic processes induces many neurodegenerative diseases such as amyotrophic lateral sclerosis, motor neuron, Huntington's, Alzheimer’s, and Parkinson's diseases. Thus, real-time quantitative analysis is of utmost importance for its prevention. In the present study, we report an enzymatic electrochemical biosensor based on reduced graphene oxide-modified nickel foam (rGO/NiF) for glutamate detection. Graphene has been successfully synthesized via electrochemical exfoliation technique using waste batteries graphite rods as a cheap, waste recycling, and environmentally friendly approach. Using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), the rGO-modified NiF electrode demonstrates improved electrocatalytic activities compared to the bare Ni foam electrode. Under the optimal conditions, the fabricated enzyme-based rGO/NiF biosensor shows a linear response in the physiological range of 5–300 µM (normal value 30–80 µM), revealing a sensitivity of ∼4.8 µA/(µM·cm2) with a correlation coefficient of ∼0.997, the limit of detection (LOD) ∼0.1 µM and shelf-life of about ten weeks. Thus, we believe that the fabrication of this sensitive and selective responding biosensor will also enable us to measure the dynamic processes associated with Glut neurotransmission in the CNS.

Tuning the carboxyl content of carbon quantum dots by an electrochemical exfoliation method to enhance Fenton-like reactions for contaminants removal in a wide pH range

The complexation of CQDs with Fe(III) through -COO-Fe bond in the CQDs-Fe(III)/H2O2 system can accelerate the Fe(III)/Fe(II) cycle and broaden the pH range for application. However, the yield and carboxyl content of CQDs prepared by conventional electrochemical exfoliation were limited, which hampered the application of CQDs and the enhancement of CQDs Fenton-like process. Hence, in this study, carboxyl-rich and high-yield CQDs were successfully prepared by electrochemical exfoliation of graphite rods in hydrogen peroxide (H2O2) solution. The results suggested that the yield and carboxyl content of the optimal CQDs (CQD@5) were 1.49 and 2.01 times those of CQDs prepared by the conventional electrochemical exfoliation method (CQD@0), respectively. Subsequently, the CQDs were applied in CQDs-Fe(III)/H2O2 systems for phenol degradation. Due to 1.73 times the carboxyl of CQD@ 5 complexing with Fe(III) than that of CQD@ 0, the kinetic constant and removal of the CQD@ 5-Fe(III)/H2O2 system for phenol degradation were 2.36 and 1.44 times those of the CQD@ 0-Fe(III)/H2O2 system at pH= 6, respectively. Under the same condition, Fe(III)/H2O2 and Fe(II)/H2O2 showed negligible degradation performance. Furthermore, the removals of phenol in the CQD@ 5-Fe(III)/H2O2 system were 1.08–7.77 times those of the CQD@ 0-Fe(III)/H2O2 system at pH= 4–8, respectively. Finally, the effect of Fe(III), CQDs, and H2O2 dosages on the phenol degradation, reusability, and universality of CQD@ 5-Fe(III)/H2O2 were investigated individually. In summary, this work provides a new method for tuning the CQDs yield and carboxyl content, which enhances pollutant degradation in CQDs-Fe(III)/H2O2 systems at a wide pH range.

Unveiling the Latest Advancements in Vanadium Carbide MXene based Supercapacitors and their Future Trends.

Vanadium-carbide-based MXenes have bewitched the scientific community due to their distinctive characteristics, which make them potential candidates for several technological applications, such as supercapacitors (SCs), batteries, gas separation, biological sensors, and desalination. This article provides an overview of recent developments in the synthesis and applications of vanadium-carbide MXene in SCs. Vanadium carbide is one of the most difficult MXenes to synthesize, and various synthesis techniques, including electrochemical exfoliation and chemical etching, have been utilized to fabricate this material. Additionally, the review article also emphasizes the potential use of vanadium carbide MXene as SCs. Finally, the paper concludes with the challenges faced in the synthesis process and the prospects of vanadium carbide MXene-based material fabrication. Overall, this review article provides in-depth and detailed information on recent research on vanadium carbide MXene and its possible uses.

All-Solution-Processed High-Performance MoS2 Thin-Film Transistors with a Quasi-2D Perovskite Oxide Dielectric.

Assembling solution-processed van der Waals (vdW) materials into thin films holds great promise for constructing large-scale, high-performance thin-film electronics, especially at low temperatures. While transition metal dichalcogenide thin films assembled in solution have shown potential as channel materials, fully solution-processed vdW electronics have not been achieved due to the absence of suitable dielectric materials and high-temperature processing. In this work, we report on all-solution-processedvdW thin-film transistors (TFTs) comprising molybdenum disulfides (MoS2) as the channel and Dion-Jacobson-phase perovskite oxides as the high-permittivity dielectric. The constituent layers are prepared as colloidal solutions through electrochemical exfoliation of bulk crystals, followed by sequential assembly into a semiconductor/dielectric heterostructure for TFT construction. Notably, all fabrication processes are carried out at temperatures below 250 °C. The fabricated MoS2 TFTs exhibit excellent device characteristics, including high mobility (>10 cm2 V-1 s-1) and an on/off ratio exceeding 106. Additionally, the use of a high-k dielectric allows for operation at low voltage (∼5 V) and leakage current (∼10-11 A), enabling low power consumption. Our demonstration of the low-temperature fabrication of high-performance TFTs presents a cost-effective and scalable approach for heterointegrated thin-film electronics.