Graphene Electrodes Research Articles

Detection of nitrite in water using Glycine-modified nanocarbon and Au nanoparticles co-modified flexible laser-induced graphene electrode

Detection of nitrite in water using Glycine-modified nanocarbon and Au nanoparticles co-modified flexible laser-induced graphene electrode

Influence of surface groups on the properties of disperse systems

Published data on the influence of surface groups on various properties of disperse systems are integrated and analyzed. The preparation of these systems is considered in relation to activated carbon. The discussion addresses the effect of redox reactions of surface groups on the energy efficiency of electrochemical supercapacitors, operation of capacitive deionization units for water desalination, and functioning of redox capacitors based on organic monomers. It is shown that very high energy and power characteristics of lithium ion capacitors are based on the redox reactions of lithium-containing surface groups of highly dispersed graphene electrodes. The effect of surface groups on the self-discharge of electrochemical supercapacitors with activated carbon-based electrodes is demonstrated. The prospects for the production of drinking water by capacitive deionization using mosaic cation/anion exchange membranes are evaluated. The practically important inversion of sulfo groups relative to the polymer chain in the catalyst layers of fuel cells with proton exchange membranes is noted.<br> The bibliography includes 181 references.

Self-powered photodetector array based on individual graphene electrode and silicon-on-insulator integration

Self-powered photodetector array based on individual graphene electrode and silicon-on-insulator integration

Effect of Magnesium Chloride in Supporting Electrolyte for Enhancing Sensitive and Selective Electrochemical Sensor: An Approach for Anti-Rheumatic Sulfasalazine Detection

In this work, an electroanalytical evaluation for voltammetric sensing of the anti-rheumatic sulfasalazine (SSZ) at an unmodified screen-printed graphene electrode (SPGE) is demonstrated. By using the differential pulse (DPV) technique, the SSZ produced a well-defined peak of around −0.3 V (vs Ag AgCl−1) in Britton-Robinson (BR) buffer pH 4. Supporting electrolytes, pH, and salts all significantly impact SSZ reduction. Therefore, their impact on the working solutions was assessed. We discovered that using a mixture of Britton–Robinson (BR) buffer with pH 4 and MgCl2 as a supporting electrolyte can enhance SSZ sensitivity by approximately 1.7 times while simultaneously increasing detection selectivity. Under optimal conditions, the proposed assay demonstrated the ultrasensitive determination of SSZ with a broad linear detection range from 0.01 to 100 μM and a low detection limit of 4.7 nM (S/N = 3). To demonstrate the impact of the proposed method, the sensor has been successfully applied for the quantitative determination of SSZ in pharmaceutical, urine, and artificial serum sample. Therefore, this approach could offer simplicity, and rapidity, and serve as an alternative to the SSZ detection in practical applications.

Electrochemical performance of gold-decorated graphene electrodes integrated with SiC

Here we investigate the interface properties of gold (Au) decorated graphenized surfaces of 4H-SiC intended for electrochemical electrodes. These are fabricated using a two-step process: discontinuous Au layers with a nominal thickness of 2 nm are sputter-deposited onto 4H-SiC substrates with different graphenization extent—zero-layer graphene (ZLG) and monolayer epitaxial graphene) —followed by thermal annealing. By performing combined morphometric analysis, Raman mapping analysis, conductive atomic force microscopy, and electrochemical impedance spectroscopy measurements, we shed light on the relationship between physical processes (Au intercalation, particle re-shaping, and de-wetting) caused by thermal annealing and the intrinsic properties of graphenized SiC (vertical electron transport, charge-transfer properties, vibrational properties, and catalytic activity). We find that the impedance spectra of all considered structures exhibit two semicircles in the high and low frequency regions, which may be attributed to the graphene/ZLG/SiC (or Au/graphene/ZLG/SiC) and SiC/ZLG/graphene/electrolyte (or SiC/ZLG//Au/electrolyte) interfaces, respectively. An equivalent circuit model is proposed to estimate the interface carrier transfer parameters. This work provides an in-depth comprehension of the way by which the Au/2D carbon/SiC interaction strength influences the interface properties of heterostructures, which can be helpful for developing high performance catalytic and sensing devices.

Efficient semi-transparent perovskite quantum dot photovoltaics enabled by asymmetric dielectric/metal/dielectric transparent electrodes

CsPbI3 perovskite quantum dots (CsPbI3-PQDs) have a high potential as semi-transparent photovoltaic absorbers because of the facile control of film thicknesses, size-tunable optical band gaps, and nanometer-scale grain sizes suppressing light scattering. Conventional semi-transparent CsPbI3-PQD solar cells showed low photovoltaic performances due to the low electrical conductivity of the graphene electrodes. Here we report that dielectric/ultra-thin metal/dielectric (DMD) electrodes with excellent optical transmittance and electrical conductivity deliver superior photovoltaic performances in the semi-transparent CsPbI3-PQD solar cells. Particularly, the asymmetric DMD electrodes composed of MoOx 15 nm/Au 10 nm/MoOx 35 nm (asym-MAM) stacks exhibit higher optical transmittance than that of the symmetric MoOx 15 nm/Au 10 nm/MoOx 15 nm (sym-MAM) stacks. The optical simulation confirms that asym-MAM stacks reduce the parasitic absorption loss in metal interlayers. Therefore, the asym-MAM stacks with a high electrical conductivity show a higher average visible transmittance (AVT) than that of the sym-MAM. Consequently, the semi-transparent CsPbI3-PQD solar cells fabricated using the asym-MAM transparent top electrodes show a power conversion efficiency of 11.3% with a considerable AVT values of 23.4% (400–800 nm) and 20.0% (380–780 nm), respectively, which were calculated from their transmittance spectra. This is the highest-efficiency semi-transparent PQD solar cells that can be used for solar window applications requiring an AVT value of over 20%.

Multifunctional Biosensing Platform Based on Nickel-Modified Laser-Induced Graphene.

Nickel plating electrolytes prepared by using a simple salt solution can achieve nickel plating on laser-induced graphene (LIG) electrodes, which greatly enhances the electrical conductivity, electrochemical properties, wear resistance, and corrosion resistance of LIG. This makes the LIG-Ni electrodes well suited for electrophysiological, strain, and electrochemical sensing applications. The investigation of the mechanical properties of the LIG-Ni sensor and the monitoring of pulse, respiration, and swallowing confirmed that the sensor can sense insignificant deformations to relatively large conformal strains of skin. Modulation of the nickel-plating process of LIG-Ni, followed by chemical modification, may allow for the introduction of glucose redox catalyst Ni2Fe(CN)6 with interestingly strong catalytic effects, which gives LIG-Ni impressive glucose-sensing properties. Additionally, the chemical modification of LIG-Ni for pH and Na+ monitoring also confirmed its strong electrochemical monitoring potential, which demonstrates application prospects in the development of multiple electrochemical sensors for sweat parameters. A more uniform LIG-Ni multi-physiological sensor preparation process provides a prerequisite for the construction of an integrated multi-physiological sensor system. The sensor was validated to have continuous monitoring performance, and its preparation process is expected to form a system for non-invasive physiological parameter signal monitoring, thus contributing to motion monitoring, disease prevention, and disease diagnosis.

Printable and recyclable carbon nanotube electronics with degradable soybean oil-based polycationic substrate as gate dielectrics

The global concern of electronic waste (e-waste) relevant to the negative impact on the environment and ecological systems have been attracted extensive attention to the imminent solution to the development of sustainable electronic devices. To deal with that, we propose renewable soybean oil to produce thermoset films, serving them as flexible green substrates for the ion-gated transistor (IGT). The effective adjustment of dielectric property and flexibility by controlling the amount of ionic moieties source gifted the thermoset with an excellent sensitivity of 8.75 × 10−3 kPa−1 while the detection limitations up to 20 kPa. Furthermore, the all-carbon-component IGT based on soybean substrate also realized with the best electrical performance of Ion/width of 0.52 μA/mm, and >250 of an on/off ratio and 2.6 μA of on-current at a low voltage operation of VDS = −0.5 V. The soybean oil-based substrate showed fast decomposition in a mildly basic solution, with the graphene electrode recapture efficiency being higher than 95% for the remaking of new transistors. The excellent working performance in both manners of the touch sensor and the field effect transistor accompanied by the highly green fabrication technology clues the high potential in the next-generation electronics that require a significant level of sustainability.

Laser-Induced Graphene Electrodes for Electrochemistry Education and Research

Many aspects of electrochemical education, such as electroanalysis demonstrations, require three-electrode-cell experimental setups. Many researchers and educators use screen-printed electrochemical electrodes, which are miniature and disposable but are relatively expensive and use proprietary fabrication components. The present article describes how to laser-scribe complete three-electrode graphene-based electrodes that can compete with (and, in some regards, even rival) commercial screen-printed electrodes. The process of optimization of the lasing procedure to produce laser-induced graphene using almost any laser cutter available to the reader is described. A way to form a Ag/AgCl pseudoreference electrode on the graphene trace to complete the three-electrode cell, without usage of commercial inks or complicated printing technologies, is demonstrated. Electrochemical characterization of the electrode surface, reference electrode stability, and student practice demonstration of analytic applications of the produced cells (determination of dopamine concentration and coffee polyphenols) are described. These experiments and procedures act both as a method of fabrication of laser-scribed electrodes and as an educational material for introduction to electrodeposition, voltammetry, and electroanalysis.

One-step fabrication of the novel electrochemical sensing platform for the ultrasensitive determination of Microcystin-LR

To ensure the safety of the natural ecosystem, it is critical to develop portable, easy-to-operate and environmentally friendly quantitative analytical electrodes for the determination of microcystin-LR (MC-LR) in environmental water. Herein, a simple, mask-free, and one-step method based on laser-induced graphene (LIG) technology is designed for the fabrication of (3D) graphene electrodes integrated with gold nanoparticles (AuNPs). The 3-electrode system with AuNPs-modified graphene was prepared directly by overlaying gold leaf on the polyimide (PI) film followed by patterned CO2 laser irradiation. The reference electrode region was then uniformly coated with Ag/AgCl paste, and the working electrode was functionalized with the aptamer through Au-S self-assembly and bonding to obtain a label-free MC-LR aptasensor. The developed MC-LR aptasensor has a detection limit of 0.053 pM and a linear range from 0.1 pM to 10 nM. Furthermore, the fabricated aptasensor presents good stability, reproducibility, specificity and detection in real samples. These sensors show great promise as a low-cost, simple and portable approve for label-free detection MC-LR in environmental samples.

Laser-induced graphene electrodes scribed onto novel carbon black-doped polyethersulfone membranes for flexible high-performance microsupercapacitors

A facile and expandable methodology was successfully developed to fabricate laser-induced graphene from novel pristine aminated polyethersulfone (amPES) membranes. The as-prepared materials were applied as flexible electrodes for microsupercapacitors. The doping of amPES membranes with various weight percentages of carbon black (CB) microparticles was then performed to improve their energy storage performance. The lasing process allowed the formation of sulfur- and nitrogen-codoped graphene electrodes. The effect of electrolyte on the electrochemical performance of as-prepared electrodes was investigated and the specific capacitance was significantly enhanced in 0.5 M HClO4. Remarkably, the highest areal capacitance of 47.3 mF·cm−2 was achieved at a current density of 0.25 mA·cm−2. This capacitance is approximately 12.3 times higher than the average value for commonly used polyimide membranes. Furthermore, the energy and power densities were as high as 9.46 µWh·cm−2 and 0.3 mW·cm−2 at 0.25 mA·cm−2, respectively. The galvanostatic charge–discharge experiments confirmed the excellent performance and stability of amPES membranes during 5,000 cycles, where more than 100% of capacitance retention was achieved and the coulombic efficiency was improved up to 96.67%. Consequently, the fabricated CB-doped PES membranes offer several advantages including low carbon fingerprint, cost-effectiveness, high electrochemical performance and potential applications in wearable electronic systems.

Fabrication of Screen‐Printed Single‐Electrode Triboelectric Nanogenerator‐Based Self‐Powered Sensor for Pulse Measurement and Its Characterization

The development of triboelectric nanogenerator technology has many benefits across various fields, particularly in healthcare applications; herein, a concise single‐electrode pulse sensor with a high output performance at a reasonable cost is suggested. The device is made up of a polydimethylsiloxane film with a spacer‐created trench structure stacked on top of a graphene‐coated polyethylene terephthalate film. A comprehensive examination of sensor fabrication together with material and electrical characterization is explained. The entire study is carried out using a graphene–silver composite electrode device, giving an output performance of ≈1.66 and ≈2.9 V for tapping movement in plain and microstructured triboelectric surfaces, respectively; however, for the graphene electrode device, the output obtained is ≈5.5 V. This wearable sensor can successfully extract the typical human wrist pulse, which displays the pressure wave from the radial artery in the range of ≈5 V with the help of an exemplary amplifier circuit and will be suitable to integrate with IoT.

High performance electro-active artificial muscles based on 3D dendritic nickel cobalt sulfide nanorods-graphene electrodes

As the desire for biomimicry that utilizes the advantages of natural organisms, increases, electroactive artificial muscles, an emerging technology, have been phasing-in to bioinspired applications in medicine, electronics, and soft robotics. However, it remains challenging to simultaneously obtain stable response characteristics and high bending displacement, considering the instability of electrode materials in open air environments. Here, 3D dendritic nickel cobalt sulfide nanorods grown on graphene electrodes, exhibiting stable electrochemical reactivity owing to their structural and material advantages, are employed to realize high-performance artificial muscles. Importantly, the significant influence of the phase transition of nickel-cobalt metals and graphene template in the synthesis steps on tuning the electrical and electrochemical properties is reported. The resulting artificial muscles show an almost 98 % enhanced bending performance and stable response to both AC and DC input signals without significant phase delay or distortion. These substantial improvements in the performance of artificial muscles enable the demonstration of bioinspired soft locomotive robots; these artificial muscles will thus expand the soft electronics industry in the field of next-generation human-machine interfaces.

Self‐Folding Graphene‐Based Interface for Brain‐Like Modular 3D Tissue

AbstractElectrophysiology of 3D neuronal cultures is of rapidly growing importance for revealing cellular communications associated with neurodevelopment and neurological diseases in their brain‐like 3D environment. Despite that the brain also exhibits an inherent modular architecture that is essential for cortical processing, it remains challenging to interface a modular network consisting of multiple 3D neuronal tissues. Here, a self‐folding graphene‐based electrode array is proposed that enables to reconstruct modular 3D neuronal tissue and investigate firing dynamics among moduli. A graphene‐sandwiched parylene‐C film self‐folds into a cylindrical structure within which living cells can be encapsulated. Culture of encapsulated cells inside the folded graphene enables to spontaneously construct 3D cell aggregates and ensure firm contact between the graphene surface and encapsulated cells. As the inner graphene surface can be utilized as an electrode, the reliable cell–electrode contact allows for long‐term electrical recording from multiple 3D aggregates. Additionally, the modular network consisting of multiple 3D aggregates exhibits richer firing patterns than a conventional homogenous 2D network, which demonstrates that the approach enables measurements of firing dynamics in complex 3D neuronal networks. The deformable graphene electrode will be a powerful platform for investigating complex cellular communications in brain‐like 3D cultures.

Novel Graphene Transfer Method to Silicone and its Sensing Application on Porous PDMS

In this work, we demonstrate a simple and sensitive parallel-plate capacitive pressure sensor fabricated on biocompatible, weather durable, elastic composite silicone and polyurethane substrate with porous polydimethylsiloxane (PDMS) dielectric made through a mixture of water as spacers. This sensor comprised a graphene electrode, which was developed through novel chemical vapor deposition on copper with hot press transfer process. The sensitivity of the sensor exhibits a positive correlation with the dielectric porosity. In addition, this device exhibits fast response time and wide dynamic window for applications. The highest sensitivity of 3.01 kPa <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> at 20% water concentration in PDMS for the dynamic range of 0–40 kPa was achieved with a response time of 0.25 s and detection resolution of 0.4 pF.

High-performance soft ionic biopolymer actuators based on sulfonated chitosan-coated electrospun silk membrane with graphene electrodes

Recently, there has been significant interest in the development of high-performance electroactive ionic actuators that possess biocompatible, biodegradable, and bio-friendly characteristics for use in human-attachable electronics. However, research on biopolymer-based soft actuators has been relatively limited due to challenges such as the low ionic conductivity of biopolymers, difficulty in processing to achieve desired functionalities, and improper mechanical stiffness. Therefore, in this study, an electrospun silk membrane coated with sulfonated chitosan, in which membrane exhibits stable mechanical and electrochemical properties due to its interdigitated structures, is utilized to realize high-performance ionic biopolymer actuators. In particular, the introduction of sulfonated chitosan-ionic liquid on electrospun silk lowers the mechanical stiffness and increases the ionic conductivity, resulting in the provision of ion pathways through the interdigitated silk-chitosan domain. On bare electrospun silk membrane, the ionic electrospun silk-sulfonated chitosan actuators with graphene-PEDOT:PSS electrodes show a 165% increase in bending performance compared to those with only PEDOT:PSS electrodes. The developed biopolymer actuator, which shows substantial improvement in actuation performance, can be a promising candidate for use in skin-attachable and biomedical devices.

Flexible B, N co-doped graphene electrodes for electrochemical detection of serotonin in bodily fluids

Real-time monitoring of neurotransmitters can offer critical information for understanding neural functions and diagnosing diseases. Herein, a flexible electrochemical biosensor suitable for detecting serotonin (5-HT) in different bodily fluids was developed based on vertical graphene co-doped with boron and nitrogen (BNVG). BNVG nanosheets were vertically grown on flexible tantalum substrates via chemical vapor deposition. The electrochemically active sites were regulated by changing the B and N contents in the BNVG film. The BNVG-based biosensor exhibited a quantitative response toward 5-HT in the pH range of 1.5–9.0. The linear concentration range of 5-HT depends on the pH, with the widest measurable concentration ranging from 0.10 to 224.43 μM. The range of 5-HT detection limits (S/N = 3) was 0.009–0.266 μM. The BNVG-based biosensor detected 5-HT in gastric juice, intestinal juice, and blood samples with high sensitivity and stability. The well-designed flexible BNVG-biointerface is an effective biosensor platform for detecting the neurotransmitter 5-HT, which can aid the development of neural electrodes and medical-care products.

Printed Graphene Electrode for ITO/MoS2/Graphene Photodiode Application

Lightweight and flexible electronics have recently emerged at the forefront of optoelectronic applications. In this regard, graphene electrodes enable opportunities for new photodiode devices. In this paper, we formulated and tested graphene ink using the standard inkjet printing technique. It was shown that the maximum conductivity of ink was achieved for 14 print passes of the graphene layer. Moreover, we deposited Molybdenum Disulfide (MoS2) ink in the same pattern and used it as an active layer. We put MoS2 ink on an Indium-Tin-Oxide (ITO) glass substrate and then deposited graphene ink as a top electrode to fabricate an ITO/MoS2/graphene device. The fabricated device showed good rectification behavior and high ON/OFF switching behavior with a max photocurrent of 15 µA at +2 V. The technique thus paves the way for low-cost, low-temperature processing of electronics and one-step fabrication.

2D Materials-based Electrochemical Triboelectric Nanogenerators.

The integration of 2D materials in triboelectric nanogenerators (TENGs) is known to increase the mechanical-to-electrical power conversion efficiency. 2D materials are used in TENGs with multiple roles as triboelectric material, charge-trapping fillers, or as electrodes. Here, novel TENGs based on few-layers graphene (FLG) electrodes and stable gel electrolytes composed of liquid phase exfoliated 2D-transition metal dichalcogenides and polyvinyl alcohol are developed. TENGs embedding FLG and gel composites show competitive open-circuit voltage (≈ 300 V), instant peak power (530 mW m-2 ), and stability (> 11 months). These values correspond to a seven-fold higher electrical output compared to TENGs embedding bare FLG electrodes. It is demonstrated that such a significant improvement depends on the high electrical double-layer capacitance (EDLC) of FLG electrodes functionalized with the gel composites. The wet encapsulation of the TENGs is shown to be an effective strategy to increase their power output further highlighting the EDLC role. It is also shown that the EDLC is dependent upon the transition metal (W vs Mo) rather than the relative abundance of 1T or 2H phases. Overall, this work lays down the roots for novel sustainable electrochemical-(e)-TENGs developed exploiting strategies typically used in electrochemical capacitors.

CVD Graphene Electrode for Direct Electrochemical Detection of Double-Stranded DNA

Understanding and regulating DNA interactions with solvents and redox-active centers opens up new possibilities for improving electrochemical signals and developing adequate biosensors. This work reports the development of a modified indium tin oxide (ITO) electrode by chemical vapor deposition (CVD) of graphene for the detection of double-stranded DNA. The modified electrode shows a better electrical conductivity than ITO, as confirmed by electrochemical impedance spectroscopy (EIS), where a drastic decrease in the charge–transfer resistance, Rct, from ~320 to ~60 Ω was observed. Sequences of double-stranded genomic DNA with a different number of base pairs are evaluated through differential pulse voltammetry (DPV), using ferri/ferrocyanide ([Fe(CN)6]3−/4−) as a mediator in the solution. Variations in the electrochemical response of the [Fe(CN)6]3−/4− probe are observed after introducing redox inactive double-stranded DNA ions. The redox-active [Fe(CN)6]3−/4− probe serves as a scaffold to bring DNA into the graphene-modified ITO electrode surface, provoking an increase in the current and a change in the potential when the number of base pairs increases. These results are confirmed by EIS, which shows a variation in the Rct. The calibration of DPV intensity and Rct vs. DNA base pairs (bps) number were linear in the 495–607 bps range. The proposed method could replace the nucleic acid gel electrophoresis technique to determine the presence of a DNA fragment and quantify its size.