Flexible Paper Electrode Research Articles

Paracetamol sensing with a flexible graphene paper electrode modified with MnCo2O4

AbstractBACKGROUNDThe design of new‐generation flexible sensors for medical applications has gained considerable interest in the research community in recent past years. Herein, a free‐standing flexible electrode was developed for the electrochemical determination of Paracetamol (PC). This graphene‐based paper electrode was prepared using graphene and MnCo2O4 dispersion with a mold‐casting method followed by chemical reduction. The morphology and structure of our flexible paper electrode (MnCo2O4/GP) were characterized by scanning electron microscopy, energy‐dispersive, X‐ray diffraction, X‐ray photoelectron, and Raman spectroscopy.RESULTSThe as‐prepared flexible MnCo2O4/GP showed outstanding sensing performance for PC, as compared to GP, due to the excellent electrochemical properties of MnCo2O4. The proposed sensor exhibited a wide linear range of 4.64–1000 μM for electrochemical determination of PC with a low detection limit of 1.39 μM. Furthermore, MnCo2O4/GP was successfully applied for PC syrup and tablets with good accuracy results.CONCLUSIONSFor the first time, the present study demonstrated the fabrication and utilization of MnCo2O4‐modified graphene paper to develop a flexible and sensitive electrode for monitoring PC. © 2024 The Author(s). Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

γ-Fe2O3 modified exfoliated graphite flexible paper based non-enzymatic glucose sensor

We report the γ-Fe2O3 modified exfoliated graphite (γ-Fe2O3@ExGCP) flexible paper electrode as a non-enzymatic glucose sensor. The γ-Fe2O3 was physically mixed with exfoliated graphite flakes, and mechanically pressed to get a thin sheet. The amperommetric analysis of γ-Fe2O3@ExGCP electrode shows that the sensor current increases with increasing glucose concentration. The impedance analysis of γ-Fe2O3@ExGCP substantiates the reduction in charge transfer resistance with increasing glucose concentration. The observed values of sensitivity for Ex-GCP and γ-Fe2O3@ExGCP electrodes are 3.51 µA mM-1cm−2 and 7.1 µA mM-1cm−2, respectively. The calculated LOD is 512 μM for γ-Fe2O3@ExGCP. Thus, γ-Fe2O3@ExGCP flexible electrode may be used for non-enzymatic glucose sensor with enhanced sensitivity.

High areal-capacitance based extremely stable flexible supercapacitors using binder-free exfoliated graphite paper electrode

The highly porous and binder-free flexible paper electrodes can enhance the specific capacitance of symmetric supercapacitors (SCs) due to their large surface and effective ion diffusion pathways. We synthesized the exfoliated graphite (ExG) by the thermal exfoliation method of chemically treated graphite flakes and compressed it into a paper-like thin sheet (binder-free) of ∼0.15 mm thickness. The coin cell SCs with copper (Cu) and stainless steel (SS) as current collectors have been fabricated for the electrochemical measurement. The cyclic voltammetry and galvanostatic charge/discharge measurements are investigated at various scan rates and current densities. The SCs with Cu foil as a current collector perform better than SS-based SCs. The Cu current collector-based SCs showed a specific capacitance of 37.08 mF cm−2, whereas it was ∼29.98 mF cm−2 for SS-based SCs at a 0.01 V s−1 scan rate across a 0–0.6 V potential window. Approximately no degradation in charge storage capacity for more than 15 000 cycles at 0.1 V s−1 shows the ultra-stability of the flexible ExG-based binder-free electrodes. A digital watch is powered using the fabricated pouch cell supercapacitor with copper-based current collectors to show the potential of SCs.

Paper-Based Electrodes to Detect Ascorbic Acid, Uric Acid, Dopamine & Biomass Derived Sugars

Multiple factors are involved in creating an electrochemical sensing device to detect various compounds. There is always a need for environmentally friendly, disposable, flexible, low-cost electrochemical sensor devices. This type of technology in the Navajo Nation is essential because it would allow them to have real-time, reliable, and cost-effective on-site detection. This would allow the Navajo Nation to detect and analyze compounds that may cause severe health issues. We fabricatehand-made flexible paper electrodes at Navajo Technical University (NTU) to detect and determine essentialbiomolecules such as ascorbic acid, dopamine, uric acid, and glucose. The materials required to fabricate these paper-based electrodes are chromatography paper, a wax printer, electrochemically active and conductive ink, electrochemistry equipment, buffer solution, and the compound being tested. First, we would get chromatography paper and print the electrode outline, designed at NTU, using the wax printer. The next step is manually coating the electrodes with the conductive ink and adding gold, copper, silver, or nickel nano-particles, which will act as catalysts. Then we deploy these electrodes to detect Glucose, Uric Acid (UA), Ascorbic Acid (AA), or Dopamine (DA) and test multiple different concentrations. We have utilized various types of electrochemical techniques like Differential pulse voltammetry (DPV), Linear Sweep Voltammetry (LSV), or Cyclic voltammetry (CV). Paper-based electrodes show noticeable results for detecting and determining these target analytes in the lab samples and real sample analysis.

Electrochemical performance of diazonium-generated carbon films for electrochemical double-layer capacitors (EDLCs)

Carbon-based electrode materials for energy storage systems have received considerable attention thanks to their excellent mechanical properties, large specific surface areas and moderate electrical conductivities. Here, diazonium-generated carbon films on the flexible carbon paper (CP) electrodes were prepared through electrochemical reduction of aryl diazonium salts bearing COOH, NO2, CH3 and H functional groups. The production of polymeric carbon films by diazonium modification method was preferred because it is a simple and effective process, and also the carbon-based films prepared by this method are covalently attached to the carbon electrode surfaces. The capacitive properties of the robust carbon films were assessed by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) in three-electrode and asymmetric device configurations. The results indicated that diazonium-generated carbon films on flexible substrates exhibited typical EDLC behavior with high specific capacitance values (237.6–446.9 F g−1 at 0.5 A g−1 current density), and also their capacitive performances were largely dependent upon the functional groups on the benzene ring. Overall, this work reveals that the diazonium modification method is a promising approach to create the carbon-based active electrode materials in advanced energy-storage systems.

Bi-MOF-Derived Carbon Wrapped Bi Nanoparticles Assembly on Flexible Graphene Paper Electrode for Electrochemical Sensing of Multiple Heavy Metal Ions.

The development of nanohybrid with high electrocatalytic activity is of great significance for electrochemical sensing applications. In this work, we develop a novel and facile method to prepare a high-performance flexible nanohybrid paper electrode, based on nitrogen-doped carbon (NC) wrapped Bi nanoparticles (Bi-NPs) assembly derived from Bi-MOF, which are decorated on a flexible and freestanding graphene paper (GP) electrode. The as-obtained Bi-NPs encapsulated by an NC layer are uniform, and the active sites are increased by introducing a nitrogen source while preparing Bi-MOF. Owing to the synergistic effect between the high conductivity of GP electrode and the highly efficient electrocatalytic activity of Bi-NPs, the NC wrapped Bi-NPs (Bi-NPs@NC) modified GP (Bi-NPs@NC/GP) electrode possesses high electrochemically active area, rapid electron-transfer capability, and good electrochemical stability. To demonstrate its outstanding functionality, the Bi-NPs@NC/GP electrode has been integrated into a handheld electrochemical sensor for detecting heavy metal ions. The result shows that Zn2+, Cd2+, and Pb2+ can be detected with extremely low detection limits, wide linear range, high sensitivity, as well as good selectivity. Furthermore, it demonstrates outstanding electrochemical sensing performance in the simultaneous detection of Zn2+, Cd2+, and Pb2+. Finally, the proposed electrochemical sensor has achieved excellent repeatability, reproducibility, stability, and reliability in measuring real water samples, which will have great potential in advanced applications in environmental systems.

Craft-and-Stick Xurographic Manufacturing of Integrated Microfluidic Electrochemical Sensing Platform

An innovative modular approach for facile design and construction of flexible microfluidic biosensor platforms based on a dry manufacturing "craft-and-stick" approach is developed. The design and fabrication of the flexible graphene paper electrode (GPE) unit and polyethylene tetraphthalate sheet (PET)6/adhesive fluidic unit are completed by an economic and generic xurographic craft approach. The GPE widths and the microfluidic channels can be constructed down to 300 μm and 200 μm, respectively. Both units were assembled by simple double-sided adhesive tapes into a microfluidic integrated GPE (MF-iGPE) that are flexible, thin (<0.5 mm), and lightweight (0.4 g). We further functionalized the iGPE with Prussian blue and glucose oxidase for the fabrication of MF-iGPE glucose biosensors. With a closed-channel PET fluidic pattern, the MF-iGPE glucose biosensors were packaged and sealed to protect the integrated device from moisture for storage and could easily open with scissors for sample loading. Our glucose biosensors showed 2 linear dynamic regions of 0.05-1.0 and 1.0-5.5 mmol L-1 glucose. The MF-iGPE showed good reproducibility for glucose detection (RSD < 6.1%, n = 6) and required only 10 μL of the analyte. This modular craft-and-stick manufacturing approach could potentially further develop along the concept of paper-crafted model assembly kits suitable for low-resource laboratories or classroom settings.

A high-performance and flexible electrode film based on bacterial cellulose/polypyrrole/nitrogen-doped graphene for supercapacitors

With the development and popularity of portable electronic devices, there is an urgent need for flexible energy storage devices suitable for mass production. We report freestanding paper electrodes for supercapacitors fabricated via a simple but efficient two-step method. Nitrogen-doped graphene (N-rGO) was first prepared via a hydrothermal method. This not only obtained nitrogen atom-doped nanoparticles but also formed reduced graphene oxide. Pyrrole (Py) was then deposited on the bacterial cellulose (BC) fibers as a polypyrrole (PPy) pseudo-capacitance conductive layer by in situ polymerization and filtered with nitrogen-doped graphene to prepare a self-standing flexible paper electrode with a controllable thickness. The synthesized BC/PPy/N15-rGO paper electrode has a remarkable mass specific capacitance of 441.9 F g−1, a long cycle life (96 % retention after 3000 cycles), and excellent rate performance. The BC/PPy/N15-rGO-based symmetric supercapacitor shows a high volumetric specific capacitance of 244 F cm−3 and a max energy density of 67.9 mWh cm−3 with a power density of 1.48 W cm−3, suggesting that they will be promising materials for flexible supercapacitors.

Inkjet-printed flexible graphene paper electrode for the electrochemical determination of mercury.

Here, we report an inkjet-printed graphene paper electrode (IP-GPE) for the electrochemical analysis of mercuric ions (Hg(ii)) in industrial wastewater samples. Graphene (Gr) fabricated on a paper substrate was prepared by a facile solution-phase exfoliation method in which ethyl cellulose (EC) behaves as a stabilizing agent. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were utilized to determine the shape and multiple layers of Gr. The crystalline structure and ordered lattice carbon of Gr were confirmed by X-ray diffraction (XRD) and Raman spectroscopy. The nano-ink of Gr-EC was fabricated on the paper substance via an inkjet printer (HP-1112) and IP-GPE was exploited as a working electrode in linear sweep voltammetry (LSV) and cyclic voltammetry (CV) for the electrochemical detection of Hg(ii). The electrochemical detection is found to be diffusion-controlled illustrated by obtaining a correlation coefficient of 0.95 in CV. The present method exhibits a better linear range of 2-100 μM with a limit of detection (LOD) of 0.862 μM for the determination of Hg(ii). The application of IP-GPE in electrochemical analysis shows a user-friendly, facile, and economical method for the quantitative determination of Hg(ii) in municipal wastewater samples.

A Novel Paper-Based Electrochemical Biosensor Based on N,O-Rich Covalent Organic Frameworks for Carbaryl Detection.

A new N,O-rich covalent organic framework (COFDHNDA-BTH) was synthesized by an amine-aldehyde condensation reaction between 2,6-dialdehyde-1,5-dihydroxynaphthalene (DHNDA) and 1,3,5-phenyltriformylhydrazine (BTH) for carbaryl detection. The free NH, OH, and C=O groups of COFDHNDA-BTH not only covalently couples with acetylcholinesterase (AChE) into the pores of COFDHNDA-BTH, but also greatly improves the catalytic activity of AChE in the constrained environment of COFDHNDA-BTH’s pore. Under the catalysis of AChE, the acetylthiocholine (ATCl) was decomposed into positively charged thiocholine (TCl), which was captured on the COFDHNDA-BTH modified electrode. The positive charges of TCl can attract anionic probe [Fe(CN)6]3−/4− on the COFDHNDA-BTH-modified electrode to show a good oxidation peak at 0.25 V (versus a saturated calomel electrode). The carbaryl detection can inhibit the activity of AChE, resulting in the decrease in the oxidation peak. Therefore, a turn-off electrochemical carbaryl biosensor based on a flexible carbon paper electrode loaded with COFDHNDA-BTH and AChE was constructed using the oxidation peak of an anionic probe [Fe(CN)6]3−/4− as the detection signal. The detection limit was 0.16 μM (S/N = 3), and the linear range was 0.48~35.0 μM. The sensor has good selectivity, repeatability, and stability, and has a good application prospect in pesticide detection.

Tuning the Redox Chemistry of Copper Oxide Nanoarchitectures Integrated with rGOP via Facet Engineering: Sensing H2S toward SRB Detection.

The ultrasensitive determination of sulfate reducing bacteria (SRB) is of great significance for their crucial roles in environmental and industrial harms together with the early detection of microbial corrosion. In this work, we report the development of highly efficient electrocatalysts, i.e., Cu2O-CuO extended hexapods (EHPs), which are wrapped on homemade freestanding graphene paper to construct a flexible paper electrode in the electrochemical sensing of the biomarker sulfide for SRB detection. Herein Cu2O-CuO EHPs have been synthesized via a highly controllable and facile approach at room temperature, where the redox centers of copper oxide nanoarchitectures are tuned via facet engineering, and then they are deposited on the graphene paper surface through an electrostatic adsorption to enable homogeneous and highly dense distribution. Owing to the synergistic contribution of high electrocatalytic activity from the Cu mixed oxidation states and abundant catalytically active facets of Cu2O-CuO EHPs and high electrical conductivity of the graphene paper electrode substrate, the resultant nanohybrid paper electrode has exhibited superb electrochemical sensing properties for H2S with a wide linear range up to 352 μM and an extremely low detection limit (LOD) of 0.1 nM with a signal-to-noise ratio of 3 (S/N = 3), as well as high sensitivity, stability, and selectivity. Furthermore, taking advantage of the good biocompatibility and mechanical flexibility, the electrochemical sensing platform based on the proposed electrode has been applied in the sensitive detection of SRB in environmental samples through the sensing of sulfide from SRB, which holds great promise for on-site and online corrosion and environmental monitoring.

Paper-supported near-infrared-light-triggered photoelectrochemical platform for monitoring Escherichia coli O157:H7 based on silver nanoparticles-sensitized-upconversion nanophosphors

Escherichia coli O157:H7 (E. coli O157:H7) is a typical foodborne pathogen that contaminates food and water, leading to lots of infectious diseases. In this study, a near-infrared-responsive photoelectrochemical (PEC) sensing platform for the ultrasensitive detection of E. coli O157:H7 was established by assembling a flexible conductive paper electrode with core-shell-structured upconversion nanophosphors (UCNPs) @SiO2@Ag and carbon self-doped graphitic carbon nitride (C-g-C3N4). In this design, UCNPs act as a self-powered that change near infrared (NIR) excitation into visible emission, while the semiconductor material C-g-C3N4 acts as the energy-conversion center to convert visible illumination to photocurrent. Importantly, silver nanoparticles (AgNPs) significantly enhance the upconversion luminescence of UCNPs and facilitate the separation and transportation of photoelectrons by the localized surface plasmon resonance effect. Using the antimicrobial peptide Magainin I as the recognition element, E. coli O157:H7 was specifically captured and determined directly for its steric hindrance effect on the photoelectrode. As a result, the photocurrent decreased linearly with the increase in E. coli O157:H7 in a wide range from 5 to 5 × 106 colony-forming units per mL (CFU/mL), and the detection limit was as low as 2 CFU/mL. Finally, the proposed NIR PEC sensor was successfully utilized for the determination of E. coli O157:H7 in contaminated pork, cabbage, and milk samples without enrichment of the bacteria in 50 min.

Fabrication of NiFeB flexible electrode via electroless deposition towards selective and sensitive detection of dopamine.

A novel cost-effective and eco-friendly flexible electrochemical sensor was designed for highly selective and sensitive detection of dopamine to deal with the problems related to serious neurological disorders. The novel flexible paper electrode with NiFeB synthesised by simple dip-coating exhibits a high sensitivity of 35.35 μA μM-1 cm-2, 2.36 μA μM-1 cm-2 and 0.215 μA μM-1 cm-2 in the linear ranges from 10 nM to 1 μM, 5 μM to 50 μM and 100 μM to 400 μM, respectively, with an ultra-low detection limit of 2.1 nM. Besides, the free-standing flexible electrode for the detection of DA, the flexible paper sensor displayed superior selectivity towards various interferents, such as ascorbic acid, glucose and uric acid, as well as stability under various deformations.

Inkjet-Printed Flexible Graphene Paper Electrode for Electrochemical Determination of Mercury in Industrial Wastewater

Inkjet-Printed Flexible Graphene Paper Electrode for Electrochemical Determination of Mercury in Industrial Wastewater

Natural fibers and reduced graphene oxide-based flexible paper electrode for energy storage applications

Natural fibers and reduced graphene oxide-based flexible paper electrode for energy storage applications

Construction of Au@PB NPs doped graphene paper as flexible electrode for real-time monitoring of living cells and biosensing platform

In this work, we report a high-performance graphene flexible paper electrode composed of core-shell Gold@Prussian blue nanoparticles (Au@PB NPs) for real-time monitoring of living cell and biosensor platform. Core-shell Au@PB NPs with high stability, low cost, excellent biocompatibility and electrochemical activity was prepared. At the same time, combined with the robust mechanical properties of reduced graphene oxide (rGO) paper, an independent flexible graphene paper electrode was prepared and broadly characterized. Because of the unique structural properties and the combinational advantages of different components in the Au@PB NPs-rGO composite, the resultant nanohybrid paper electrode exhibits good electrochemical sensing performance toward hydrogen peroxide (H2O2) and it also displays a very short response time (1 s) in the tracking of H2O2 secretion by living HepG2 cells. Meanwhile, the as-prepared Au@PB NPs-rGO paper electrode can be further used as an enzyme-based biosensor. In this regard, glucose oxidase (GODx) used as an example for glucose detection and analysis, which proves its excellent performance as an enzyme sensing platform. The excellent properties of the kind of nanocomposites are expected to be further used in the field of flexible devices and Point-of-Care (POC).

Flexible paper-based Ni-MOF composite/AuNPs/CNTs film electrode for HIV DNA detection

It is very important to develop a rapid, simple, low cost point-of-care (POC) method for the early diagnosis of pathogens. In this work, a flexible paper-based electrode based on nickel metal-organic framework (Ni-MOF) composite/Au nanoparticles/carbon nanotubes/polyvinyl alcohol (Ni–Au composite/CNT/PVA) was constructed to detect target human immunodeficiency virus (HIV) DNA by DNA hybridization using methylene blue (MB) as a redox indicator. The CNT/PVA and Ni–Au composite were deposited on the cellulose membrane by vacuum filtration and drop-coating method in turn to obtain Ni–Au composite/CNT/PVA (CCP) film electrode. Compared to the CNT/PVA film electrode, CCP film electrode makes a higher loading of the probe DNA for its large specific surface area and conjugated π-electron system that can provide hydrogen bond sources to achieve interactions between MOF and single-stranded DNA, which improves the sensitivity for detecting target DNA. The variation of peak current for MB molecules adsorbed onto DNA before and after hybridization with HIV DNA was monitored. Electrochemical results proved that the CCP film maintained stable electrochemical property even after bending 200 times or stretching under different strains from 0% to 20%. The flexible paper electrode showed excellent sensing performance with a linear range of 10 nM–1 μM and a low detection limit of 0.13 nM. The target HIV DNA was successfully detected even in complex serum samples using the flexible CCP film electrode. Therefore, the simple and inexpensive flexible paper-based MOF composite film electrode can also be utilized for other pathogens POC diagnosis.

Effect of roughness on the conductivity of vacuum coated flexible paper electrodes

AbstractFlexible conducting materials are required for the design and fabrication of a host of applications involving flexible electronic items. A flexible substrate like paper or polymer is generally employed for deposition of metal by a variety of processes. Among many physical properties, the roughness of the substrate is considered an important parameter, although, its exact role on effective conductivity of the coating is not known. Nor any study has been carried out to understand how the three‐dimensional porous structure of the substrate surface affects the microscopic packing of grains that constitute the metal coating. With the objective of elucidating the effect of substrate roughness on the conductivity of paper electrodes, we have used six different commonly available papers for vacuum coating with copper. For a smooth substrate, the grains that constitute the coating appear spherical, however, turns ellipsoidal as the substrate roughness and heterogeneity is increased; ellipsoidal grains result in higher packing efficiency leading to higher conductivity. We have also presented a model to relate the packing efficiency to the asphericity, polydispersity, and skewness of size distribution of grains.

Low-cost flexible laminated graphene paper solid-contact ion-selective electrodes

We report here the fabrication of laminated graphene paper solid-contact ion-selective electrodes (SCISE) with performance characteristics equal to the state of the art SCISEs. Several identical and flexible graphene paper electrodes were first prepared from commercially available graphene paper with a standard pouch laminator in a single lamination step to a price of less than $1 per electrode. After that the solid contact consisting of polyaniline (PANI) doped with dinonylnaphthalene sulfonic acid and the K+-selective plasticized poly(vinyl chloride) membrane were deposited in two steps by drop casting on the surface of the graphene paper. The lamination of 10–15 identical graphene paper electrodes takes only one minute and we obtained fully functional graphene paper electrodes in ca. 40 min, including all manual pre-fabrication steps and 10 min of argon plasma cleaning to remove organic contaminants from the graphene surface. We found that plasma cleaning was necessary to improve the reversibility of the electron transfer of the Fe(CN)63−/4− redox couple. The laminated graphene paper K-SCISEs had a Nernstian slope of 56.9 ± 0.1 mV pK-1, a high E° reproducibility of ±4.4 mV (n = 6) still after more than 24 h, high selectivity against Na+, Li+, H+, Mg2+ and Ca2+, and they showed no water layer formation, light and oxygen gas sensitivity.· However, we observed a minor response to carbon dioxide (pH) because of the pH response of PANI. In this work, we show that laminated graphene paper electrodes are a cost-effective alternative for example to commercially available glassy carbon and platinum rod electrodes.

Flexible graphene paper electrode prepared via polyvinyl alcohol-assisted shear-exfoliation for all-solid-state polymer supercapacitor application

Herein, an environmentally-benign, facile, efficient, low-cost, scalable fabrication process of achieving flexible graphene paper electrode at ambient conditions is reported. By means of high-shear exfoliation of graphite in aqueous polyvinyl alcohol (PVA), the graphene/PVA dispersion is prepared. Various characterizations (transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, etc.) confirm that the resulting dispersion is with the presence of high-quality, single to few-layered graphene sheets with thickness up to 1.68 nm, lateral size of 0.5–2 μm, and low defect density (ID/IG = 0.09). Further, the applicability of the in-situ exfoliated graphene/PVA dispersion is demonstrated for the fabrication of flexible conductive paper electrodes through a simple intermittent soaking-drying approach. The graphene paper electrode possesses an electrical sheet resistance of 15 Ω sq−1, without any additional annealing treatment and conductive additives. Finally, the graphene paper electrode is integrated with ionic-liquid incorporated PVA polymer electrolyte to develop the all-solid-state supercapacitor. It imparts a considerable specific capacitance of 222.96 F g−1 along with ~60% capacitance retention and ~100% coulombic efficiency after 6000 charge–discharge cycles. Meanwhile, the polymer electrolyte exhibits a remarkable ionic conductivity (4.63 × 10−4 S cm−1) together with a wide electrochemical stability window (5.1 V), favorable for device applications. The unique interwoven nanoporous conductive network of PVA-stabilized exfoliated graphene provides fast diffusion pathways to electrolyte ions, thus significantly enhancing the charge-storage performance.