Flexible Graphene Paper Research Articles

Synergy of modulating in-plane pores and zincophilic sites on the flexible graphene paper for efficient and dendrite-free hosted Zn anode

The practical advancement of Zn-ion batteries (ZIBs) in the portable/wearable electronics field is still hindered by the notorious Zn dendrites formation and the lack of an appropriate host to construct a highly effective flexible Zn anode. Herein, we present a three-dimensional (3D) N-doped graphene paper framework with abundant in-plane pores (rHGP-N) as an efficient Zn plating/stripping scaffold. Remarkably, the rHGP-N paper electrode exhibits an unprecedentedly low Zn nucleation overpotential of 5.2 mV and maintains a high average Coulombic efficiency (∼99.3%) over a superior long Zn plating/stripping cycling of 1400 h. DFT calculation results demonstrate that pyrrolic-nitrogen on graphene possesses the strongest adsorption energy for Zn2+, serving as zincophilic sites to guide Zn uniform nucleation. Moreover, the finite elements simulation results illustrate that flexible graphene paper with abundant in-plane pores can mitigate structural stress and inhibit the formation of Zn dendrites by spatially homogenizing Zn2+ ions flux throughout the entire electrode. The assembled ZIBs full cell (rHGP-N@Zn//rHGP-N@Mn3(PO4)2) demonstrates an impressive volumetric energy density of 77 mWh/cm3, as well as excellent flexibility and mechanical stability with negligible capacity decay under harsh deformation conditions. Our approach can be potentially utilized in designing dendrite-free metal-based flexible anodes for Mg, Ca, or Al-ion batteries.

Flexible Graphene Paper Modified Using Pt&Pd Alloy Nanoparticles Decorated Nanoporous Gold Support for the Electrochemical Sensing of Small Molecular Biomarkers.

The exploration into nanomaterial-based nonenzymatic biosensors with superb performance in terms of good sensitivity and anti-interference ability in disease marker monitoring has always attained undoubted priority in sensing systems. In this work, we report the design and synthesis of a highly active nanocatalyst, i.e., palladium and platinum nanoparticles (Pt&Pd-NPs) decorated ultrathin nanoporous gold (NPG) film, which is modified on a homemade graphene paper (GP) to develop a high-performance freestanding and flexible nanohybrid electrode. Owing to the structural characteristics the robust GP electrode substrate, and high electrochemically catalytic activities and durability of the permeable NPG support and ultrafine and high-density Pt&Pd-NPs on it, the resultant Pt&Pd-NPs-NPG/GP electrode exhibits excellent sensing performance of low detection limitation, high sensitivity and anti-interference capability, good reproducibility and long-term stability for the detection of small molecular biomarkers hydrogen peroxide (H2O2) and glucose (Glu), and has been applied to the monitoring of H2O2 in different types of live cells and Glu in body fluids such as urine and fingertip blood, which is of great significance for the clinical diagnosis and prognosis in point-of-care testing.

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.

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.

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

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).

Electrochemical fabrication of polyaniline/graphene paper (PANI/GP) supercapacitor electrode materials on free-standing flexible graphene paper

Free-standing flexible supercapacitive electrodes have practical application for wearable energy storage devices. In this paper, graphene paper (GP), a flexible electrode substrate, was prepared by one-step reduction of graphene oxide (GO) using HI solution. GP can be used independently as a flexible electrode with specific capacitance of 227 F/g. In order to make up for the shortage of GP specific capacitance storage, polyaniline (PANI) with high specific capacitance and good electrical conductivity was selected to composite with GP by electrochemical polymerization approach. This method to fabricate electrode material by direct electrochemical polymerization avoids the use of conductive binder and organic solvent. Owing to the specific capacitance contribution of PANI and GP, the PANI/GP composites exhibit higher specific capacitance when the polymerization time is 30 s and the polymerization voltage is 0.8 V. At 1 A/g current density, the specific capacitance of composite is up to 759 F/g, which is 3.34 times of neat GP.

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.

Ni-Co-N hybrid porous nanosheets on graphene paper for flexible and editable asymmetric all-solid-state supercapacitors

Great attention has been drawn to flexible and portable electronic devices, so it is important to develop flexible energy-storage devices. In this study, the porous Ni-Co-N nanosheets on flexible graphene paper (GP) are prepared by surface nitridation of NiCo2O4 nanosheets. Compared with NiCo2O4/GP, Ni3N/GP and CoN/GP, Ni-Co-N/GP shows superior performance in terms of specific capacitance of 960 F/g (48.1 mF/cm2) at 4 A/g, rate performance (86% capacitance retention) and cycle life (the capacitance retention reaches 95% over 5000 cycles). The paper-based all-solid-state asymmetric supercapacitors (SCs) are manufactured based on Ni-Co-N/GP and chemical oxidized GP (graphene oxide paper, GOP), which exhibits excellent bendability, flexibility, editability. The flexible energy device shows an outstanding specific energy of 4.78 mWh/cm3 and excellent cycle life (89% capacitance retention after 8000 cycles).

Two-dimensional graphene paper supported flexible enzymatic fuel cells.

Application of enzymatic biofuel cells (EBFCs) in wearable or implantable biomedical devices requires flexible and biocompatible electrode materials. To this end, freestanding and low-cost graphene paper is emerging among the most promising support materials. In this work, we have exploited the potential of using graphene paper with a two-dimensional active surface (2D-GP) as a carrier for enzyme immobilization to fabricate EBFCs, representing the first case of flexible graphene papers directly used in EBFCs. The 2D-GP electrodes were prepared via the assembly of graphene oxide (GO) nanosheets into a paper-like architecture, followed by reduction to form layered and cross-linked networks with good mechanical strength, high conductivity and little dependence on the degree of mechanical bending. 2D-GP electrodes served as both a current collector and an enzyme loading substrate that can be used directly as a bioanode and biocathode. Pyrroloquinoline quinone dependent glucose dehydrogenase (PQQ-GDH) and bilirubin oxidase (BOx) adsorbed on the 2D-GP electrodes both retain their biocatalytic activities. Electron transfer (ET) at the bioanode required Meldola blue (MB) as an ET mediator to shuttle electrons between PQQ-GDH and the electrode, but direct electron transfer (DET) at the biocathode was achieved. The resulting glucose/oxygen EBFC displayed a notable mechanical flexibility, with a wide open circuit voltage range up to 0.665 V and a maximum power density of approximately 4 μW cm−2 both fully competitive with reported values for related EBFCs, and with mechanical flexibility and facile enzyme immobilization as novel merits.

Flexible freestanding graphene paper-based potentiometric enzymatic aptasensor for ultrasensitive wireless detection of kanamycin

Flexible sensing devices have drawn tremendous attention in the past decades due to their potential applications in future hand-held, potable consumer, and wearable electronics. Here, we firstly developed an ultrasensitive wireless potentiometric aptasensor based on flexible freestanding graphene paper for kanamycin detection. Flexible graphene paper made from a simple vacuum filtration method was used as a biocompatible platform for effective immobilization of aptamer. A nuclease-assisted amplification strategy was introduced into this potentiometric biosensing system in order to significantly improve the detection sensitivity through a classic catalytic recycling reaction of target induced by the nuclease (DNase I). As expected, an ultra-low detection limit of 30.0 fg/mL for kanamycin was achieved. Furthermore, the developed potentiometric enzymatic aptasensor exhibits high selectivity, favorable flexibility, excellent stability and reproducibility, which holds great promising for its routine sensing application.

Facile and green synthesis of highly conducting graphene paper

A free-standing, highly flexible and conductive graphene paper (GrP) was fabricated via a simple, green, and inexpensive method. The fabrication process starts with electrochemical exfoliation of graphite as partially oxidized graphene suspension, which is then vacuum-filtered and air-dried. The procedure does not warrant any binders, toxic and corrosive agents, or high temperature. The mechanically stable GrP has excellent tensile strength of 52.3 ± 2.3 MPa at peak elongation of 5.1 ± 0.4%; ultralow sheet resistance of 2.2 Ω sq−1, which is highly stable changing by only ∼4% even after 1000 consecutive bending cycles at 10 mm bending radius; and high electrical conductivity of 3.85 × 105 S m−1. The GrP also possesses high specific capacitance of 195.8 F g−1 at 1 mV s−1 in 1 M H2SO4 as electrolyte at room temperature with Pt wire and Ag/AgCl as counter and reference electrodes, respectively. Moreover, the GrP can reusably absorb large amounts of oils and organic solvents. This environmentally friendly GrP fabrication method is of low cost and can be used for large-scale fabrication for applications such as energy-storage devices, flexible/wearable electronics, and removal of oil or toxic organic spills.

Freestanding and flexible graphene papers as bioelectrochemical cathode for selective and efficient CO2 conversion

During microbial electrosynthesis (MES) driven CO2 reduction, cathode plays a vital role by donating electrons to microbe. Here, we exploited the advantage of reduced graphene oxide (RGO) paper as novel cathode material to enhance electron transfer between the cathode and microbe, which in turn facilitated CO2 reduction. The acetate production rate of Sporomusa ovata-driven MES reactors was 168.5 ± 22.4 mmol m−2 d−1 with RGO paper cathodes poised at −690 mV versus standard hydrogen electrode. This rate was approximately 8 fold faster than for carbon paper electrodes of the same dimension. The current density with RGO paper cathodes of 2580 ± 540 mA m−2 was increased 7 fold compared to carbon paper cathodes. This also corresponded to a better cathodic current response on their cyclic voltammetric curves. The coulombic efficiency for the electrons conversion into acetate was 90.7 ± 9.3% with RGO paper cathodes and 83.8 ± 4.2% with carbon paper cathodes, respectively. Furthermore, more intensive cell attachment was observed on RGO paper electrodes than on carbon paper electrodes with confocal laser scanning microscopy and scanning electron microscopy. These results highlight the potential of RGO paper as a promising cathode for MES from CO2.

Graphene paper for exceptional EMI shielding performance using large-sized graphene oxide sheets and doping strategy

Large-sized graphene sheets (LG) and doping strategy were employed to fabricate lightweight and flexible graphene paper with exceptional electromagnetic interference (EMI) shielding performance. Compared with the smaller sized ones, LG with fewer defects and more conjugated carbon domain size as well as better alignment result in higher electrical conductivity and strength of graphene paper. The iodine doping further improves the carrier density of LG by formation of triiodide (I3−) and pentaiodide (I5−) through charge transfer process without deteriorating the mechanical property, thus leading to superior EMI shielding effectiveness (SE). The EMI SE of iodine doped LG film with thickness of 12.5 μm is up to ∼52.2 dB at 8.2 GHz, which is much higher than that of undoped LG with the same thickness (∼47.0 dB). More important, the improvements in EMI SE is contributed to the SE absorption, while the SE reflection is almost unchanged. The mechanisms of improved EMI shielding performance as well as mechanical property were investigated and discussed. The present study provides a facile way to fully develop graphene in lightweight and flexible EMI shielding materials and devices.

Flexible, Free‐Standing and Holey Graphene Paper for High‐Power Supercapacitors

AbstractFlexible supercapacitors based on bendable electrodes have aroused much interest for integration in clothing materials and portable electronic devices. However, simultaneous achievement of high areal energy and high power densities still presents a great challenge. Herein we report the fabrication of free‐standing, flexible graphene papers suitable for high‐performance flexible supercapacitors. The binder‐free graphene paper is made up of two types of holey graphene units (i.e., wrinkled graphene sheets and graphene nanoscrolls) that produce closely interconnected, porous 3D graphene architectures. The graphene papers reported here can be fabricated with a variety of thicknesses and areal densities, in the 10–70 μm and 1–5 mg cm−2 ranges, respectively. They exhibit a remarkable electrochemical performance in aqueous electrolytes: a) a high cell areal capacitance (230–190 mF cm−2 in H2SO4 and 180–170 mF cm−2 in Li2SO4), b) an outstanding capacitance retention of 60 % at ultra‐large current densities of 1200 mA cm−2, c) an excellent long‐term cycling stability and d) high areal power (≈280 mW cm−2) and energy densities (≈32 and ≈60 μWh cm−2 in H2SO4 and Li2SO4, respectively). These highly flexible graphene papers show a great improvement, in terms of areal energy‐power densities, in relation to the state‐of‐the‐art graphene‐based film electrodes.

Conjunction of Conducting Polymer Nanostructures with Macroporous Structured Graphene Thin Films for High-Performance Flexible Supercapacitors.

Fabrication of hybridized structures is an effective strategy to promote the performances of graphene-based composites for energy storage/conversion applications. In this work, macroporous structured graphene thin films (MGTFs) are fabricated on various substrates including flexible graphene papers (GPs) through an ice-crystal-induced phase separation process. The MGTFs prepared on GPs (MGTF@GPs) are recognized with remarkable features such as interconnected macroporous configuration, sufficient exfoliation of the conductive RGO sheets, and good mechanical flexibility. As such, the flexible MGTF@GPs are demonstrated as a versatile conductive platform for depositing conducting polymers (CPs), e.g., polyaniline (PAn), polypyrrole, and polythiophene, through in situ electropolymerization. The contents of the CPs in the composite films are readily controlled by varying the electropolymerization time. Notably, electrodeposition of PAn leads to the formation of nanostructures of PAn nanofibers on the walls of the macroporous structured RGO framework (PAn@MGTF@GPs): thereafter, the PAn@MGTF@GPs display a unique structural feature that combine the nanostructures of PAn nanofibers and the macroporous structures of RGO sheets. Being used as binder-free electrodes for flexible supercapacitors, the PAn@MGTF@GPs exhibit excellent electrochemical performance, in particular a high areal specific capacity (538 mF cm(-2)), high cycling stability, and remarkable capacitive stability to deformation, due to the unique electrode structures.

Synthesis of flexible pure graphene papers and utilization as free standing cathodes for lithium-air batteries

In Lithium-air cathode, graphene containing materials have been reported as ideal cathode materials due to their large theoretical specific surface area, chemical stability, high electrical conductivity and charge capacity. In this study; three free-standing flexible graphene cathodes were produced with different thickness by vacuum filtration technique. For preparation of the graphene electrodes, graphene oxide (GO) papers were chemically reduced. Surface morphology of the produced graphene cathodes were characterized using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) was conducted to understand elemental composition of the GO paper. X-ray diffraction (XRD) technique and Raman spectroscopy were carried out to investigate the structure of the GO paper electrode. Moreover, specific surface area and porosity distribution of the GO paper was performed using Brunauer–Emmett–Teller (BET) method from N2 adsorption and desorption isotherms and the pore size were calculated using the Barrett–Joyner–Halenda (BJH) algorithm on the desorption branch. Electrochemical performance of the free-standing graphene electrodes were assessed in ECC-Air test cell from 1.5 V to 4.5 V at a constant current density.

Free-standing and flexible graphene papers as disposable non-enzymatic electrochemical sensors

We have explored AuNPs (13nm) both as a catalyst and as a core for synthesizing water-dispersible and highly stable core–shell structural gold@Prussian blue (Au@PB) nanoparticles (NPs). Systematic characterization by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) disclosed AuNPs coated uniformly by a 5nm thick PB layer. Au@PB NPs were attached to single-layer graphene oxide (GO) to form Au@PB decorated GO sheets. The resulting hybrid material was filtered layer-by-layer into flexible and free-standing GO paper, which was further converted into conductive reduced GO (RGO)/Au@PB paper via hydrazine vapour reduction. High-resolution TEM images suggested that RGO papers are multiply sandwich-like structures functionalized with core–shell NPs. Resulting sandwich functionalized graphene papers have high conductivity, sufficient flexibility, and robust mechanical strength, which can be cut into free-standing electrodes. Such electrodes, used as non-enzymatic electrochemical sensors, were tested systematically for electrocatalytic sensing of hydrogen peroxide. The high performance was indicated by some of the key parameters, for example the linear H2O2 concentration response range (1–30μM), the detection limit (100nM), and the high amperometric sensitivity (5Acm−2M−1). With the advantages of low cost and scalable production capacity, such graphene supported functional papers are of particular interest in the use as flexible disposable sensors.