Graphene Electrodes Research Articles

Hybrid Paper/Polyester‐Based Laser‐Induced Graphene Electrodes for Electrochemical Detection of Tadalafil

Here, we describe for the first time the fabrication of laser‐induced graphene (LIG) electrodes on a hybrid substrate composed of sandpaper and polyester. As a proof of concept, the proposed device was used as a voltammetric sensor for tadalafil (TAD) quantification in authentic tablet samples. . The electrochemical TAD sensing based on differential pulse voltammetry (DPV) revealed a linear behavior in the concentration range from 25 to 250 μmol L‐1 (R2 = 0.99), a limit of detection of ~ 9.6 μmol L‐1, sensitivity of ~ 0.0048 µA(µmol L‐1)‐1 and acceptable reproducibility values (RSD ≤ 5.8%). The DPV responses involving the standard addition method in pharmaceutical samples presented recovery results of TAD ranging from 93 to 108%. Also, the proposed analytical method offered a suitable green analytical chemistry profile. We successfully demonstrated the fabrication of graphene‐like sites and nanoparticles composed of alumina upon a hybrid substrate.

Smart electrochemical determination of food additive (Propyl gallate) in edible oil and chicken samples based on CoSe2@FeS2 nanocomposite modified laser induced graphene electrode

BackgroundThe overuse of synthetic phenolic antioxidants has negative health impacts on individuals. Several sensors have been developed to detect and monitor the level of these substances, frequently necessitating labour-intensive procedures and lengthy processes. MethodsHere, a simple and cost-effective electrode based on CoSe2 and FeS2 nanoparticles which could be actuated by a smart portable device has been developed. CoSe2 nanocorals and FeS2 nanosheets were successfully synthesised through hydrothermal technique and mechanically hybridized. The prepared CoSe2@FeS2 nanocomposite was used to modify the glassy carbon electrode (GCE), and the modified electrode was deployed to sense propyl gallate (PG). The electrochemical characteristics of the fabricated sensor were then studied through cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Significant findingsThe sensor resulted in a current response that covered a broad linear range from 0.05 μM to 200 μM and had a low detection limit (LOD) of 0.018 μM and a limit of quantification (LOQ) of 0.064 μM with outstanding performance. The designed electrode material was then used to modify the laser-induced graphene electrode (LIGE) and employed to evaluate its practical applicability. The findings exhibited efficient detection with commendable recovery rates thus the designed electrode could be a game changer in the portable-smart sensing of propyl gallate.

Mechanism of SDBS functionalized PPy enhancing the electrochemical sensitivity of SPGE to dopamine and uric acid: Experimental and DFT investigations

A novel approach to enhance the electrochemical sensitivity of screen-printed graphene electrode (SPGE) to dopamine (DA) and uric acid (UA) utilizing sodium dodecylbenzene sulfonate (SDBS) functionalized polypyrrole (PPy) is presented. The functionalized PPy nanosheets (SDBS/PPy) were synthesized via low-temperature polymerization. The introduced dodecylbenzene sulfonate (DBS-) facilitated the dispersion of functionalized PPy nanosheets, resulting in a notably increased specific surface area. DA and UA adsorption behavior on PPy and SDBS/PPy surface was investigated using density functional theory (DFT). The adsorption energy of DA and UA on SDBS/PPy was 0.15 eV and 0.05 eV higher than that on PPy. The adsorption ability of DA and UA was greatly improved after doping DBS- in PPy. The electrochemical response of SDBS/PPy-modified SPGE (SDBS/PPy/SPGE) to different concentrations of DA and UA was evaluated. Compared with SPGE, the oxidation current sensitivity of SDBS/PPy/SPGE to DA increased from 0.08 μA·μM−1 to 0.13 μA·μM−1, the oxidation current sensitivity of SDBS/PPy/SPGE to UA increased from 0.01 μA·μM−1 to 0.04 μA·μM−1. Electrochemical measurement demonstrated that PPy doping with DBS- caused a unique improvement in DA and UA performance of SPGE.

Rapid Quantification of Antioxidant Capacity in Tea Using Laser-Induced Graphene Electrodes

Rapid Quantification of Antioxidant Capacity in Tea Using Laser-Induced Graphene Electrodes

Super-efficient and stable detection of toxic heavy metal by polyethylenimine-modified graphene electrode sensor

Super-efficient and stable detection of toxic heavy metal by polyethylenimine-modified graphene electrode sensor

Gold-modified laser-scribed lettuce-like graphene electrodes for ultrasensitive detection of bioactive molecules

Gold-modified laser-scribed lettuce-like graphene electrodes for ultrasensitive detection of bioactive molecules

Enhancing the capacitance and robustness of graphene supercapacitors by adding a coating of activated-carbon/Bi2Al4O9 on their electrodes

Recently, using activated carbon (AC) for supercapacitors (SCs) has attracted attention because such carbon can be easily derived from bio-waste. However, the capacitance of the AC based SCs is in general low. For this reason, we present in this research the synthesis of AC from aquatic water-lily plant, which is considered a pest. First, SCs were fabricated only with graphene electrodes and produced a capacitance (Cs)/Energy-density (E) of 150.3 F g-1/30.1 Wh kg-1. Later, a coating of AC was deposited on the graphene electrodes and now the devices had higher Cs and E of 446.7 F g-1 and 89.4 Wh kg-1, respectively. The Cs/E of the devices was enhanced even more to 641.9 F g-1/128.3 Wh kg-1 after depositing a composite powder of AC/Bi2Al4O9 (BiAl) on the SC electrodes. Thus, the capacitance increased by 197% and 327% after introducing AC and AC/BiAl to the SCs. Other benefits of introducing the AC/BiAl composite to the electrodes were: i) the output voltage was enhanced 40% with respect to the device made with only AC; ii) the capacitance retention for 1000 bending cycles was maintained over 95%, this means that adding the AC/BiAl to the SC electrodes increased the mechanical resistance/stability of the devices; iii) the SCs produced a constant operating voltage of 0.33 V when they immersed in motor oil, which is not commonly reported in the literature; and iv) the SCs maintained a voltage of 0.37 when they are subjected to bending in real time. If no BiAl is added to the SC electrodes, the output voltage is lower (0.15 V). On the other hand, Raman and XPS spectroscopies demonstrated that the devices made with AC/BiAl had on their electrodes oxygen vacancies and chemical species such as: Bi5+/Bi3+/Bi0 and Al3+/Al0, which worked as redox centers for the charge storage. In general, this work demonstrated that it is possible the fabrication of AC-based SCs with capacitances that surpass the values already reported in literature for devices made with AC (50–150 F g-1). Also, we confirmed that adding BiAl to the system increased the robustness (mechanical/electrochemical stability) of the devices, which is of interest for the flexible electronics.

Changes in Current Transport and Regulation of the Microstructure of Graphene/Polyimide Films under Joule Heating Treatment.

The excellent electrical properties of graphene have received widespread attention. However, the difficulty of electron transfer between layers still restricts the application of graphene composite materials to a large extent. Therefore, in this study, graphene/polyimide films were subjected to a Joule heating treatment to improve the electrical conductivity of the film by ~76.85%. After multiple Joule thermal cycle treatments, the conductivity of the graphene/polyimide film still gradually increased, but the increase in amplitude tended to slow down. Finally, after eight Joule heat treatments, the conductivity of the graphene/polyimide film was improved by ~93.94%. The Joule heating treatment caused the polyimide to undergo atomic rearrangement near the interface bonded to the graphene, forming a new crystalline phase favourable for electron transport with graphene as a template. Accordingly, a model of the bilayer capacitive microstructure of graphene/polyimide was proposed. The experiment suggests that the Joule heating treatment can effectively reduce the distance between graphene electrode plates in the bilayer capacitive micro-nanostructures of graphene/polyimide and greatly increases the number of charge carriers on the electrode plates. The TEM and WAXS characterisation results imply atomic structure changes at the graphene/polyimide bonding interface.

Study on the performance of biochar prepared from walnut shell and traditional graphene electrode plate in the treatment of domestic sewage in microbial fuel cells.

As a new pollutant treatment technology, microbial fuel cell (MFC) has a broad prospect. In this article, the devices assembled using walnut shells are named biochar-microbial fuel cell (B-MFC), and the devices assembled using graphene are named graphene-microbial fuel cell (G-MFC). Under the condition of an external resistance of 1,000 Ω, the B-MFC with biochar as the electrode plate can generate a voltage of up to 75.26 mV. The maximum power density is 76.61 mW/m2, and the total internal resistance is 3,117.09 Ω. The removal efficiency of B-MFC for ammonia nitrogen (NH3-N), chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) was higher than that of G-MFC. The results of microbial analysis showed that there was more operational taxonomic unit (OTU) on the walnut shell biochar electrode plate. The final analysis of the two electrode materials using BET specific surface area testing method (BET) and scanning electron microscope (SEM) showed that the pore size of walnut shell biochar was smaller, the specific surface area was larger, and the pore distribution was smoother. The results show that using walnut shells to make electrode plates is an optional waste recycling method and an electrode plate with excellent development prospects.

Size-dependent electrochemistry of laser-induced graphene electrodes

Laser-induced graphene (LIG) electrodes have become popular for electrochemical sensor fabrication due to their simplicity for batch production without the use of reagents. The high surface area and favorable electrocatalytic properties also enable the design of small electrochemical devices while retaining the desired electrochemical performance. In this work, we systematically investigated the effect of LIG working electrode size, from 0.8 mm to 4.0 mm diameter, on their electrochemical properties, since it has been widely assumed that the electrochemistry of LIG electrodes is independent of size above the microelectrode size regime. The background and faradaic current from cyclic voltammetry (CV) of an outer-sphere redox probe [Ru(NH3)6]3+ showed that smaller LIG electrodes had a higher electrode roughness factor and electroactive surface ratio than those of the larger electrodes. Moreover, CV of the surface-sensitive redox probes [Fe(CN)6]3– and dopamine revealed that smaller electrodes exhibited better electrocatalytic properties, with enhanced electron transfer kinetics. Scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy showed that the physical and chemical surface structure were different at the electrode center versus the edges, so the electrochemical properties of the smaller electrodes were improved by having rougher surface, more density of the graphitic edge planes, and more oxide-containing groups. The difference could be explained by the different photothermal reaction time from the laser scribing process that causes different stable carbon morphology to form on the polymer surface. Our results give a new insight on relationships between surface structure and electrochemistry of LIG electrodes and are useful for designing miniaturized electrochemical devices.

High‐Performance SiC/Graphene UV‐Visible Band Photodetectors with Grating Structure and Asymmetrical Electrodes for Optoelectronic Logic Gate

AbstractHigh‐quality epitaxial graphene is prepared on semi‐insulated 4H‐SiC (0001) by ultra‐high vacuum thermal decomposition method and used in graphene/SiC/graphene ultraviolet‐visible dual‐band photodetectors. The dual‐band detector exhibits an extremely low dark current (5.2 × 10−14 A) and a peak responsivity of 1.17 A W−1 corresponding to an external quantum efficiency of 518%. A high detectivity of 3.14 × 1014 Jones is achieved under 280 nm light illumination at 30 V, while a high response speed is obtained with a rise time of 25.17 ns and a decay time of 540.10 ns. The detector shows a responsivity of 1.4 × 10−5 A W−1 and a detectivity of 6.5 × 109 Jones under 430 nm light illumination. The dual‐band detector equipped with SiC grating and asymmetrical graphene electrodes is demonstrated for high‐performance optoelectronic logic “AND” gate with high detectivity at 280 and 430 nm.

Atomistic insights into the superior performance of C60-decorated graphene supercapacitors

Properties of graphene-based supercapacitors decorated with ▪ fullerenes and three different electrolytes based on ▪ cation and two different anions (▪ and ▪) were investigated by atomistic molecular dynamics simulations. Our simulations reveal that the electrolyte first layer near the electrode, which is made up of the region decorated with fullerenes, is a key factor in explaining the remarkable performance of electrodes coated with ▪ fullerenes. The access of the electrolyte between the interstitial spaces formed between the ▪ molecules provides a network of extended and intense electrostatic interactions that do not exist in a pure graphene electrode. The study demonstrates that ▪ molecules are effective in creating small pores in the graphene sheets, which permit ion mobility while retaining the structural and electrostatic characteristics that are consistent with the experimentally measured values. Notably, this engineered porosity has proven to significantly increase the electrical response at the interface, dramatically improving device performance. These simulation results provide a better understanding of the ▪ porosity of the electrode and the performance of the graphene/▪-based supercapacitor.

Development of pectin-based gel electrolyte for wireless electrochemical determination of cadmium and lead using smartphone

A portable device offering effortlessness, mobility, and affordability for real-time and on-site monitoring of heavy metals is currently in great demand to maintain environmental sustainability. Herein, a platform utilizing a biopolymeric gel-based electrolyte for the on-field simultaneous determination of Cd(II) and Pb(II) is described. Pectin, a natural polymer, was exploited as a chemical delivery medium on account of its biodegradability, environmental friendliness, and rapid dissolving characteristics. The gel electrolyte was prepared by having pectin dissolved in KCl mixed with Sb(III)–Bi(III) bimetallic alloy solution, and casted onto a paper substrate. An in situ bimetallic alloy and pre-mixed bismuth nanoparticles modified screen-printed graphene electrode (Sb–Bi/BiNP/SPGE) were employed to enhance the electrochemical signals of Cd(II) and Pb(II) for the differential pulse anodic stripping voltammetry (DPASV). It was demonstrated that the platform was capable of generating sharp and well-defined current signals, achieving the low detection limits of 50.98 ng mL−1 for Cd(II) and 40.80 ng mL−1 for Pb(II). The reproducibility, as indicated by the relative standard deviation, was found to be less than 10.4 % (n = 10) for the developed gel-based device when coupled with a wireless near field communication (NFC) potentiostat. Lastly, the obtained sensor was applied for quantification of Cd and Pb in potentially contaminated groundwater samples. The recoveries obtained were satisfactorily within the acceptable range. The newly designed platform exhibited several advantages, including small sample volume (μL), low-cost, no sample preparation requirements, and being environmentally friendly. The convenience of a portable device utilizing the proposed biopolymeric gel-based electrolyte for on-field analysis makes it highly appealing for various applications.

Towards sustainable and humane dairy farming: A low-cost electrochemical sensor for on-site diagnosis of milk fever

Milk fever is a metabolic disorder that predominantly affects dairy animals during the periparturient period and within four weeks of calving. Milk fever is primarily attributed to a decrease in the animal's serum Ca2+ levels. Clinical milk fever occurs when Ca2+ concentration drops below 1.5 mM (6 mg/dL). Without prompt intervention, clinical milk fever leads to noticeable physical symptoms and health complications including coma and fatality. Subclinical milk fever is characterized by Ca2+ levels between 1.5 and 2.12 mM (6–8.48 mg/dL). Approximately 50% of multiparous dairy cows suffer from subclinical milk fever during the transition to lactation. The economic impact of milk fever, both direct and indirect, is substantial, posing challenges for farmers. To address this issue, we developed a low-cost electrochemical sensor that can measure bovine serum calcium levels on-site, providing an opportunity for early detection of subclinical and clinical milk fever and early intervention. This calcium sensor is a scalable solid contact ion sensing platform that incorporates a polymeric calcium-selective membrane and ionic liquid-based reference membrane into laser-induced graphene (LIG) electrodes. Our sensing platform demonstrates a sensitivity close to the theoretical Nernstian value (29.6 mV/dec) with a limit of detection of 15.6 μM and selectivity against the species in bovine serum. Moreover, our sensor can detect Ca2+ in bovine serum with 91% recovery.

Biolayer-Interferometry-Guided Functionalization of Screen-Printed Graphene for Label-Free Electrochemical Virus Detection.

Additive manufacturing holds promise for rapid prototyping and low-cost production of biosensors for diverse pathogens. Among additive manufacturing methods, screen printing is particularly desirable for high-throughput production of sensing platforms. However, this technique needs to be combined with carefully formulated inks, rapid postprocessing, and selective functionalization to meet all requirements for high-performance biosensing applications. Here, we present screen-printed graphene electrodes that are processed with thermal annealing to achieve high surface area and electrical conductivity for sensitive biodetection via electrochemical impedance spectroscopy. As a proof-of-concept, this biosensing platform is utilized for electrochemical detection of SARS-CoV-2. To ensure reliable specificity in the presence of multiple variants, biolayer interferometry (BLI) is used as a label-free and dynamic screening method to identify optimal antibodies for concurrent affinity to the Spike S1 proteins of Delta, Omicron, and Wild Type SARS-CoV-2 variants while maintaining low affinity to competing pathogens such as Influenza H1N1. The BLI-identified antibodies are robustly bound to the graphene electrode surface via oxygen moieties that are introduced during the thermal annealing process. The resulting electrochemical immunosensors achieve superior metrics including rapid detection (55 s readout following 15 min of incubation), low limits of detection (approaching 500 ag/mL for the Omicron variant), and high selectivity toward multiple variants. Importantly, the sensors perform well on clinical saliva samples detecting as few as 103 copies/mL of SARS-CoV-2 Omicron, following CDC protocols. The combination of the screen-printed graphene sensing platform and effective antibody selection using BLI can be generalized to a wide range of point-of-care immunosensors.

Empowering an Acute Kidney Injury 3D Graphene-Based Sensor Using Extreme Learning Machine.

This study reports on the application of an extreme learning machine (ELM) in near-real-time kidney monitoring via urine neutrophil gelatinase-associated lipocalin (NGAL) detection with a 3D graphene electrode. This integration marks the first instance of combining a graphene-based electrode with machine learning to enhance the NGAL detection accuracy, building on our group's 2020 research. The methodology involves two key components: a graphene electrode functionalized with a lipocalin-2 antibody for NGAL detection and the ELM application for improved prediction accuracy by using urine analysis data. The results show a significant 15% increase in the area under the curve (AUC) for NGAL determination, with error reduction from ±6 to 0.54 ng/mL within a linear range of 2.7-140 ng/mL. The ELM also lowered the detection limit from 14.8 to 0.89 ng/mL and increased accuracy, precision, sensitivity, specificity, and F1 score for AKI prediction by 8.89, 30.69, 6.78, 9.94, and 19.07%, respectively. These findings underscore the efficacy of simple neural networks in enhancing graphene-based electrochemical sensors for AKI biomarkers. ELM was chosen for its optimal performance-resource balance, with a comparative analysis of ELM, support vector machines, multilayer perceptron, and random forest algorithms also included. This research suggests the potential for miniaturizing AI-enhanced sensors for practical applications.

Tunneling current-controlled spin states in few-layer van der Waals magnets.

Effective control of magnetic phases in two-dimensional magnets would constitute crucial progress in spintronics, holding great potential for future computing technologies. Here, we report a new approach of leveraging tunneling current as a tool for controlling spin states in CrI3. We reveal that a tunneling current can deterministically switch between spin-parallel and spin-antiparallel states in few-layer CrI3, depending on the polarity and amplitude of the current. We propose a mechanism involving nonequilibrium spin accumulation in the graphene electrodes in contact with the CrI3 layers. We further demonstrate tunneling current-tunable stochastic switching between multiple spin states of the CrI3 tunnel devices, which goes beyond conventional bi-stable stochastic magnetic tunnel junctions and has not been documented in two-dimensional magnets. Our findings not only address the existing knowledge gap concerning the influence of tunneling currents in controlling the magnetism in two-dimensional magnets, but also unlock possibilities for energy-efficient probabilistic and neuromorphic computing.

Flexible laser-induced graphene electrodes on polyimide film: Hybrid nanoflower-modified dielectric microjunctions for non-faradaic analysis

Laser-induced Graphene (LIG) electrodes on flexible substrates have attracted significant research interest, making them an excellent alternative to conventional fabrication of transducers on rigid planar substrates. In this study, four individual capacitor-like triangular LIG electrodes were fabricated on polyimide (PI) film with micron gap (MG) spacing of 30, 66, 125 and 180 µm, to study the relationship between gap spacing and capacitance. A novel N, N-carbonyldiimidazole-copper (CDI-Cu) hybrid nanoflower (NF) was synthesised via one-pot biomineralization and deposited at the triangular junction of acid-base treated LIG-MG for the immobilization of neutravidin. The gap spacing and structure of the LIG-MG were analysed using high-resolution microscopes, revealing a porous nanofiber-like graphene structure. X-ray Photoelectron Spectroscopy (XPS) of acid-base treated PI film proved carboxyl group formation. A decrease in capacitance was observed with an increasing gap spacing in a non-faradaic environment. The capacitance of CDI-Cu NF following neutravidin modification for 30, 66, 125 and 180 µm spacings were 1.77E-07, 1.36E-07, 4.73E-08, 4.84E-08 F, respectively, suggesting excellent biomolecular modification sensitivity of the LIG-MG with 30 µm spacing. A comparative analysis of dielectric performance for different gap-spaced devices revealed that a 30 µm spacing would be optimal for bio-capturing because of the close confinement of biomolecules for smaller gapped areas.

Molecular insight into sequence-defined polyelectrolytes for energy storage devices

Polyelectrolyte (PE) adsorption on charged surfaces is a complex phenomenon that has an array of applications ranging from healthcare to designing energy storage devices. PE adsorption on surfaces involves surface charge polarization effects which arise due to the dielectric dissimilarities between the PE and the charged surface. PEs owing to their high potential window, and leakage-resistant behavior are used as supercapacitor electrolytes. Recent experimental evidence suggests co-block polymers as potential design materials for energy storage devices (ESDs). It is imperative to mention that the structural variation of the co-block polymers under spatial confinements will have a key role in designing electrodes and electrolytes for ESDs which demands a detailed investigation. This study reveals that the spatial orientations of the charged groups have an impressive impact on the changes in PE charge density peaks, charge amplification peaks, PE adsorption, counter-ion adsorption, and differential and integral capacitance while confined by graphene electrodes. It is startling to observe that the counter-ion distribution within the electrical double layer of the positively charged surface significantly depends on the orientation of the PEs. However, with increasing solvent dielectric constant the variations in the above-mentioned properties subside due to reduced electrostatic interactions. The differential capacitance and the integral capacitance are also found to be dependent on the dielectric constants of the solvent. These findings will be immensely useful in determining the key factors needed to describe the preferred spatial configuration of a PE suitable for various ESDs and applications involving PEs in a confined system.

In situ patterning of nickel/sulfur-codoped laser-induced graphene electrode for selective electrocatalytic valorization of glycerol

The electrocatalytic valorization of glycerol is an emerging upcycling process for the biomass utilization. In this work, nickel/sulfur-codoped laser-induced graphene (LINiSG) on flexible polyimide film was fabricated and demonstrated as a self-supported and binder-free monolithic electrode for electrocatalytic glycerol oxidation reaction (EGOR) towards the selective generation of value-added three-carbon (C3) chemicals. The laser-induced in-situ and synchronous carbonization of polysulfone and Ni precursor was demonstrated to remarkably promote both the electrochemical surface area and Ni loading of LINiSG electrode. These synergistic merits are considered as the main origin for its enhanced EGOR activity and stability, showing much smaller Tafel slope and 2-fold enhanced current density, as compared to LINiG electrode without the co-carbonization of polysulfone. The influence of experimental parameters has been systematically investigated by the product analysis, achieving an average 94.7 % C3 selectivity and 76.1 % C3 Faradaic efficiency with a high selectivity of dihydroxyacetone (ca. 67.7 %) in near-neutral conditions, which is better than most of the reported EGOR electrodes operated in near-neutral conditions. This work demonstrated the viability of using flexible self-supported and binder-free LIG electrode with rational design and preparation approach for electrocatalytic valorization of biomass.