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Herein, an environment friendly paper-based biobattery is demonstrated that yields a power of 12.5W/m3. Whatman filter papers were used not only as support for electrode fabrication but also as separator of the biobattery. To provide electrical conductivity to the paper-based cathode and anode, commercially available eyeliner containing carbon nanoparticles and Fe3O4 was directly employed as conductive ink without any binder. With an instant start-up, the as-fabricated biocompatible electrodes could hold bacteria in an active form at the anode allowing chemical oxidation of organic fuel producing current. The facile process delineated here can be employed for the tailored electrode fabrication of various flexible energy harnessing devices.

In this work, we detail the progress of a novel electrochemical disposable device, which has a relatively low cost and easy production, with a novel conductive ink, that consists of graphite and automotive varnish mixture, deposited over a self-adhesive paper, granting an easy production with relatively low cost. The electrode surface was characterized by scanning electron microscopy, X-ray powder diffraction and Fourier transforms infrared and Raman, cyclic voltammetry and electrochemical impedance spectroscopies. In addition, the proposed electrode was applied for individual electrochemical determination of dopamine and serotonin. The device achieved a linear response between 30 and 800 μmol L−1 and a limit of detection (LOD) of 0.13 μmol L−1, by square wave voltammetry for dopamine and a linear range from 6.0 to 100 μmol L−1, with a LOD of 0.39 μmol L−1, by differential pulse voltammetry for serotonin. Later, the working electrode was modified with glucose oxidase and dihexadecyl phosphate film in order to obtain a biosensor. At this stage, CV was applied to detect glucose in the range of 1.0–10 μmol L−1 and LOD of 0.21 μmol L−1. By three different techniques and analytes, the sensoring and biosensoring processes presented high reproducibility. The proposed adhesive electrode is easy to prepare, disposable, within non-restrictive nature, which allows an approach of a new device for electrochemical sensing and biosensing.

We have reported the fabrication of flexible graphene-paper electrode (GPE) with a flat surface, whose internal structure has been formed with gradient porous build-up (from the surface to the 2-hydroxyethyl cellulose (HC)-coated paper). HC solution was used as a binder to form the gradient porous graphene layer, enabling it to create an anchoring force between the porous graphene layer and the filter paper. The morphology of GPE was investigated using a scanning electron microscope, and the surface resistance of the GPE as a function of graphene content was determined using four-probe method. The electrochemical performance of the GPE was evaluated using a three-electrode test cell by cyclic voltammetry. The gravimetric capacitance of GPE was found to be 120 F per gram of graphene, and the capacitance retention was within ca. 96% for over 500 cycles. This could be attributed to both the low surface resistance resulting from the flat surface and the high electrochemical activity caused by the gradient porous structure. This unique structure not only offers an enhanced conductivity and good electrical contact between the electrode and electrolyte but also helps GPE to maintain good cyclic stability, proving its potential for use in various rechargeable and portable energy-storage devices.

Low cost disposable working electrodes are specifically desired for practical applications of electrochemical detection considering maturity of electrochemical stations and data collection protocols. In this paper double-sided conductive adhesive carbon tape with nanostructure was applied to fabricate disposable working electrodes. Being supported by indium tin oxide glass, the prepared carbon tape electrodes were coated with bismuth film for stripping analysis of heavy metal ions. By integrating the bismuth modified electrodes with paper-based analytical devices, we were able to differentiate Zn, Cd and Pb ions with the sample volume of around 15 μL. After the optimization of parameters, including modification of bismuth film and the area of the electrodes, etc., Pb ions could be measured in the linear range from 10 to 500 μg/L with the detection limit of 2 μg/L. Our experimental results revealed that the disposable modified electrodes could be used to quantify migrated lead from toys with the results agreed well with that using atomic absorption spectrometry. Although bismuth modification and stripping analysis could be influenced by the low conductivity of the carbon tape, the low cost disposable carbon tape electrodes take the advantages of large-scaled produced double-sided carbon tape, including its reproducible nanostructure and scaled-up fabrication process. In addition, the preparation of disposable electrodes avoids time-consuming pretreatment and experienced operation. This study implied that the carbon tape might be an alternative candidate for practical applications of electrochemical detection.

The growing demand for compact point-of-care medical devices and portable instruments for on-site environmental sampling has stimulated intense research on flexible sensors that can be miniaturized and function under considerable physical deformation. We report a new type of flexible electrochemical biosensors based on free-standing graphene paper carrying binary nanocomposites of PtAu alloy and MnO 2 . The coral-like PtAu–MnO 2 nanocomposites are grown on the substrate through one-step template-free electrodeposition, leading to an intimate contact between the PtAu alloy and MnO 2 matrix. The flexible electrode exhibits a unique set of structural and electrochemical properties such as better uniformity, larger active surface areas, and faster electron transfer in comparison with the control electrode prepared by tandem growth of MnO 2 network and PtAu alloy in two steps. In nonenzymatic amperometric glucose detection, the PtAu–MnO 2 binary nanostructure-decorated graphene paper has shown greatly enhanced sensing performance such as wide liner range (0.1 mM to 30.0 mM), high sensitivity (58.54 μA cm −2 mM −1 ), low detection limit (0.02 mM, S / N =3), satisfactory selectivity, excellent reproducibility and stability, and tolerability to mechanical stress. The strategy of co-growth of metal and metal oxides on freestanding carbon substrates opens new possibility to develop high-performance flexible electrochemical sensors.

Dual-signal amplification strategy for ultrasensitive electrochemiluminescence (ECL) multiplexed immunoassay on microfluidic paper-based analytical devices (μ-PADs) was demonstrated. This dual-signal amplification technique was achieved by employing graphene oxide-chitosan/gold nanoparticles (GCA) immunosensing platform and [4,4'-(2,5-dimethoxy-1,4-phenylene)bis(ethyne-2,1-diyl) dibenzoic acid] (P-acid) functionalized nanoporous silver (P-acid/NPS) signal amplification label. For further low-cost and disposable applications, battery-triggered constant-potential ECL (+1.0V for P-acid label (vs. Ag/AgCl auxiliary electrode)) was applied on this paper-based immunodevice with the aid of a home-made voltage-tunable power device, allowing the traditional electrochemical workstation to be abandoned. We found that two tumor markers could be sequentially detected in the linear ranges of 0.003-20 and 0.001-10ngmL(-1) with the detection limits down to 1.0 and 0.8pgmL(-1), respectively, by simply reversing the connection mode on two working electrodes. The results exhibited excellent precision and high sensitivity of such immunoassay, and it also demonstrated that this battery-triggered ECL paper-based immunodevice could provide a rapid, simple and simultaneous multiplex immunoassay with high throughput, low-cost and low detection limits for point-of-care testing.

A facile and green method was developed to synthesize the graphene-carbon nanotubes (Gr-CNTs) nanocomposite with a sandwich lamination structure. Pt nanoparticles were loaded on the as-synthesized Gr-CNTs nanocomposite to prepare an electrochemical sensor for determining bisphenol A (BPA) in thermal printing paper. The electrochemical behavior of BPA on the Pt/Gr-CNTs nanocomposite was investigated by cyclic voltammetry (CV) and chronocoulometry (CC). The direct determination of BPA was accomplished by using differential pulse voltammetry (DPV) under optimized conditions. The oxidation peak current was proportional to the BPA concentration in the range from 6.0 × 10(-8) to 1.0 × 10(-5) M and 1.0 × 10(-5) to 8.0 × 10(-5) M with a correlation coefficient of 0.987 and 0.998, respectively. The detection limit was 4.2 × 10(-8) M (S/N = 3). The fabricated electrode showed good reproducibility, stability and selectivity. The proposed method was successfully applied to determine BPA in thermal printing papers samples and the results were satisfactory.

Genetic analysis is of great importance for the detection of pathogenic bacteria. Bacterial identification must become simpler, less expensive, and more rapid than the traditional methods. In this study, a low-cost, label-free, and wireless paper-based bipolar electrode electrochemiluminescence (pBPE-ECL) analysis system was constructed for the rapid and sensitive genetic detection of pathogenic bacteria. Wax-screen printing was used to form hydrophilic channels on filter paper, and a carbon ink-based bipolar electrode and driving electrodes were screen-printed into the channels. The “light-switch” molecule [Ru(phen)2dppz]2+ (phen = 1,10-phenanthroline; dppz = dipyridophenazine) was used to intercalate into the base pairs of the double-stranded DNA PCR amplification products, and the complexs were then applied to the paper-based bipolar electrode to perform the ECL assays; the ECL of [Ru(phen)2dppz]2+ is quenched in aqueous solution, but this molecule displays intense ECL when intercalated into double-str...

A novel, unique, truly-solid Li-ion cell structural design, based on LiFePO4/graphite electrodes and profoundly ionic conducting polymer electrolyte, is fabricated by exploiting, for the first time, carbonised cellulose nanofibrils as both the conductive binder and the current collector substrate. Moreover, cellulose nanofibrils are used as reinforcing additive for the preparation of the unconventional composite polymer electrolyte separator. The resulting solid polymeric lab-scale Li-ion cell, assembled in a “pouch cell” envelop, shows remarkably stable characteristics upon prolonged cycling at ambient temperature even at high current regimes. By the way, a simple procedure, easily scalable, is optimized for the spray coating and water-based papermaking. As a result, all components can be fully recovered at the end of the cell operational life by taking advantage of a simple water-based paper recycling technique, opening new horizons for the manufacture of sustainable electrochemical energy storage devices.

This paper studies Fe/Al composite hydrogel electrode electrocoagulation (EC) and adsorption of alizarin red S (ARS). ARS removal efficiency and degradation mechanism when applying Fe/Al composite hydrogel electrode were investigated. The optimum experimental factors and degradation of ARS were discussed. ARS degradation was optimal operation at initial pH 3 with O2.The experimental results showed that the COD removal efficiency was better, reaching to about 90 % when applying the novel electrode system. The discoloration rate also reached the best effect of 99 % in the superior technical conditions. The optimum electrolysis time is about 30 min. Results revealed that the efficiency in the EC process with Fe/Al composite hydrogel electrodes were much better than that in conventional electrode system. In addition, Fe/Al composite hydrogel electrodes are environment-friendly material, which reuse waste and reduce cost. Hydrogel has certain iron exchange capacity to eliminate the residual metal irons. It is found that the application of ultrasonic helps to accelerate the electrocoagulation of ARS. This study not only realizes the ultrasonic, flotation, coagulation, and adsorption of the combination but also gains economy and environment. Consequently, the unique performance of Fe/Al composite hydrogel electrodes opens promising perspectives for fast, high, and economical treatment of wastewater containing dyes or/and organic contaminants.

For the first time, a paper based enzymatic fuel cell is used as self-recharged supercapacitor. In this supercapacitive enzymatic fuel cell (SC-EFC), the supercapacitive features of the electrodes are exploited to demonstrate high power output under pulse operation. Glucose dehydrogenase-based anode and bilirubin oxidase-based cathode were assembled to a quasi-2D capillary-driven microfluidic system. Capillary flow guarantees the continuous supply of glucose, cofactor and electrolytes to the anodic enzyme and the gas-diffusional cathode design provides the passive supply of oxygen to the catalytic layer of the electrode. The paper-based cell was self-recharged under rest and discharged by high current pulses up to 4mAcm−2. The supercapacitive behavior and low equivalent series resistance of the cell permitted to achieve up to a maximum power of 0.87mWcm−2 (10.6mW) for pulses of 0.01s at 4mAcm−2. This operation mode allowed the system to achieve at least one order of magnitude higher current/power generation compared to the steady state operation.

We report the development of an electrochemical paper-based analytical device (ePAD) for the selective determination of dopamine (DA) in model serum sample. The ePAD device consists of three layers. In the top layer, SU-8 photoresist defines a hydrophilic sample application spot on the filter paper. The middle layer was made from transparency film and contained two holes, one for sample preconcentration and the other for the surfactant to allow transfer to the third layer. A screen-printed carbon electrode formed the bottom layer and was used for electrochemical measurements. In the absence of the anionic surfactant, sodium dodecyl sulfate (SDS), the oxidation peaks of DA, ascorbic acid (AA) and uric acid (UA) overlapped. With the addition of SDS, the DA oxidation peak shifted to more negative values and was clearly distinguishable from AA and UA. The oxidation potential shift was presumably due to preferential electrostatic interactions between the cationic DA and the anionic SDS. Indeed, whilst the SDS-modified paper improved the DA current five-fold, the non-ionic Tween-20 and cationic tetradecyltrimethylammonium bromide surfactants had no effect or reduced the current, respectively. Furthermore, only the SDS-modified paper showed the selective shift in oxidation potential for DA. DA determination was carried out using square-wave voltammetry between -0.2 and 0.8 V vs. Ag/AgCl, and this ePAD was able to detect DA over a linear range of 1-100 μM with a detection limit (S/N=3) of 0.37 μM. The ePAD seems suitable as a low cost, easy-to-use, portable device for the selective quantitation of DA in human serum samples.

A novel method to fabricate graphene paper with folded structured graphene sheets is described. When used as an electrode for LIBs and supercapacitors, the as-prepared graphene paper can show much higher performances compared to conventional graphene paper fabricated by a flow-directed assembly method. The unique graphene paper obtained here is promising to act as a new kind of flexible electrode for wearable or rolling-up devices.

A sensitive and fast-responding membrane-free amperometric gas sensor is described, consisting of a small filter paper foil soaked with a room temperature ionic liquid (RTIL), upon which three electrodes are screen printed with carbon ink, using a suitable mask. It takes advantage of the high electrical conductivity and negligible vapour pressure of RTILs as well as their easy immobilization into a porous and inexpensive supporting material such as paper. Moreover, thanks to a careful control of the preparation procedure, a very close contact between the RTIL and electrode material can be achieved so as to allow gaseous analytes to undergo charge transfer just as soon as they reach the three-phase sites where the electrode material, paper supported RTIL and gas phase meet. Thus, the adverse effect on recorded currents of slow steps such as analyte diffusion and dissolution in a solvent is avoided. To evaluate the performance of this device, it was used as a wall-jet amperometric detector for flow injection analysis of 1-butanethiol vapours, adopted as the model gaseous analyte, present in headspace samples in equilibrium with aqueous solutions at controlled concentrations. With this purpose, the RTIL soaked paper electrochemical detector (RTIL-PED) was assembled by using 1-butyl-3- methylimidazolium bis(trifluoromethanesulfonyl)imide as the wicking RTIL and printing the working electrode with carbon ink doped with cobalt(ii) phthalocyanine, to profit from its ability to electrocatalyze thiol oxidation. The results obtained were quite satisfactory (detection limit: 0.5 ?M; dynamic range: 2-200 ?M, both referring to solution concentrations; correlation coefficient: 0.998; repeatability: ±7% RSD; long-term stability: 9%), thus suggesting the possible use of this device for manifold applications. © 2012 The Royal Society of Chemistry.

We present a high-capacity pseudocapacitor based on a hierarchical network architecture consisting of Co(3)O(4) nanowire network (nanonet) coated on a carbon fiber paper. With this tailored architecture, the electrode shows ideal capacitive behavior (rectangular shape of cyclic voltammograms) and large specific capacitance (1124 F/g) at high charge/discharge rate (25.34 A/g), still retaining ~94% of the capacitance at a much lower rate of 0.25 A/g. The much-improved capacity, rate capability, and cycling stability may be attributed to the unique hierarchical network structures, which improves electron/ion transport, enhances the kinetics of redox reactions, and facilitates facile stress relaxation during cycling.

A novel electrochemiluminescence (ECL) "sandwich" biosensor has been developed to detect cocaine. The sandwich biosensor was fabricated on the basis of the fact that a single aptamer could be split into two fragments and the two dissociated parts could form a folded, associated complex in the presence of targets. One of these (capture probe), which had hexane-thiol at its 5'-terminus, was immobilized on a gold electrode via thiol-gold binding. The other one (detection probe) was labeled with the ECL reagent tris(2,2'-bipyridyl)ruthenium(II)-doped silica nanoparticles (RuSiNPs) at its 3'-terminus. Owing to the weak interaction between the two fragments, the sensor exhibited a low ECL signal in the absence of cocaine. After the target cocaine had been added to the solution, it induced association of the two fragments and stabilized the associated complexes, leading to immobilization of RuSiNPs on the electrode surface, and the ECL detected on the electrode surface was enhanced. The enhanced ECL intensity was directly proportional to the logarithm of the cocaine concentration in the range from 1.0 × 10(-9) to 1.0 × 10(-11) mol/L, with a detection limit of 3.7 × 10(-12) mol/L. The biosensor was applied to detect trace amounts of cocaine on banknotes with satisfactory results.

Gas diffusion media (GDM) and flow fields perform the task of distributing the reactant gases uniformly over the active electrochemical area in proton exchange membrane (PEM) fuel cells. Carbon paper and carbon cloth are two commonly employed gas diffusion media in PEM fuel cells, and they differ widely in their structure and properties. Since the path of the reactant gases to the catalyst in the fuel cell electrodes involves passing through the flow fields as well as the GDM, a good design for a fuel cell requires an understanding of the interaction between these components. The focus of the present work is to study the impact of the difference in structure and properties of the diffusion media used, on the design of the PEM fuel cell flow field. Carbon paper and carbon cloth were characterized for the pressure drop they cause when used as GDMs, for channel intrusion, compressibility and electrical resistivity. Carbon cloth exhibits about 43-125% more intrusion into the channel in comparison with carbon paper for the conditions tested. This intrusion results in increased pressure drop in the flow channel especially at higher channel widths and at higher compression. Compression studies reveal that carbon cloth lacks compression rigidity and suffers considerable strain at lower stress values whereas carbon paper is relatively rigid in nature. The results indicate that the intrusion of carbon cloth into the channel, constraints the channel width in a flow field design if it were to be used with a carbon cloth GDM as opposed to a carbon paper GDM. Electrical resistivity measurements were carried out and a simple mathematical model has been developed for the potential drop in the GDM. The model indicates that even from the perspective of electrical properties, use of carbon cloth GDM constraints the channel width that is permissible in flow field design. � 2010 Elsevier Ltd.

Paper surfaces (Whatman filter papers, Kimwipes®, and Japanese Washi papers) were employed as support for gold nanoparticles (AuNPs) deposited by the seed-mediated growth method. The AuNP-modified paper or textile was brought into “weak” (or non-permanent) contact with a glassy carbon electrode and immersed into aqueous electrolyte media. Electrochemical responses for the Fe(CN)64−/Fe(CN)63− redox system in 0.1 M phosphate buffer (pH 7.0) and 1.0 M KCl solutions were investigated by voltammetry and impedance methods. Even for weakly contacted AuNP catalysts of relatively low density faster electron transfer was observed. Particle sizes of at least 20 nm diameter were required. There was no permanent contact from AuNP catalysts to the electrode and the process was therefore termed “weak contact catalysis”. The method is proposed as a rapid and novel catalyst screening tool with potential applications in fuel cell and sensor technologies. Keywords: Modified electrodes, Gold nanoparticles, Electron-transfer reactions, Textile, Paper, Catalyst support, Seed-mediated growth method, Voltammetry, Impedance, Contact-electrocatalysis

This article describes the preparation and characterization of PEDOT-coated paper electrodes. Their specific behavior was investigated, especially the impact of electrode shape on the electrochemical properties. It was found that different electrode geometries promote different results, largely because of a potential drop in the bulk of the electrode material. More importantly, the suitability of these substrates for bio- and neurochemical analyses was investigated. The paper electrodes were found to offer better resistance to both protein and neurotransmitter foulings, in comparison to a planar electrode. Interestingly, long paper electrodes were more stable during sustained oxidation of dopamine and serotonin than short ones, possibly because of the conjunction of surface passivation and potential drop allowing for the site of oxidation to move along the electrode as fouling progresses.

We report the first demonstration of electrochemical detection for paper-based microfluidic devices. Photolithography was used to make microfluidic channels on filter paper, and screen-printing technology was used to fabricate electrodes on the paper-based microfluidic devices. Screen-printed electrodes on paper were characterized using cyclic voltammetry to demonstrate the basic electrochemical performance of the system. The utility of our devices was then demonstrated with the determination of glucose, lactate, and uric acid in biological samples using oxidase enzyme (glucose oxidase, lactate oxidase, and uricase, respectively) reactions. Oxidase enzyme reactions produce H2O2 while decomposing their respective substrates, and therefore a single electrode type is needed for detection of multiple species. Selectivity of the working electrode for H2O2 was improved using Prussian Blue as a redox mediator. The determination of glucose, lactate, and uric acid in control serum samples was performed using chronoamperometry at the optimal detection potential for H2O2 (0 V versus the on-chip Ag/AgCl reference electrode). Levels of glucose and lactate in control serum samples measured using the paper devices were 4.9 +/- 0.6 and 1.2 +/- 0.2 mM (level I control sample), and 16.3 +/- 0.7 and 3.2 +/- 0.3 mM (level II control sample), respectively, and were within error of the values measured using traditional tests. This study shows the successful integration of paper-based microfluidics and electrochemical detection as an easy-to-use, inexpensive, and portable alternative for point of care monitoring.

The properties of the interlayer and outer layer of Ti/Co/SnO2-Sb2O5 electrode were studied, and the electrochemical behavior was examined as well. As a result of unsatisfactory treatment using Ti/Co/SnO2-Sb2O5 electrode, electrochemical disposal of paper mill wastewater employing three-dimensional electrodes, combining active carbon granules serving as packed bed particle electrodes, with Ti/Co/SnO2-Sb2O5 anode, was performed. The outcome demonstrates that efficient degradation was achieved. The residual dimensionless chemical oxygen demand (COD) concentration reached 0.137, and color removal 75% applying 167 mA cm(-2) current density at pH 11 and 15 g l(-1) NaCl. The instant current efficiency, energy cost, electrochemical oxidation index (EOI) and kinetic constant of the reaction were calculated. At the same time, the influence of pH and current density on COD abatement and decolorization was also investigated, respectively.

A strategy that combines visible-light-enhanced biofuel cells (BFCs) and electrochemical immunosensor into paper-based analytical devices was proposed for sensitive detection of the carbohydrate antigen 15-3 (CA15-3). The gold nanoparticle modified paper electrode with large surface area and good conductibility was applied as an effective matrix for primary antibodies. The glucose dehydrogenase (GDH) modified gold-silver bimetallic nanoparticles were used as bioanodic biocatalyst and signal magnification label. Poly(terthiophene) (pTTh), a photoresponsive conducting polymer, served as catalyst in cathode for the reduction of oxygen upon illumination by visible light. In the bioanode, electrons were generated through the oxidation of glucose catalyzed by GDH. The amount of electrons is determined by the amount of GDH, which finally depended on the amount of CA15-3. In the cathode, electrons from the bioanode could combine with the generated holes in the HOMO energy level of cathode catalysts pTTh. Meanwhile, the high energy level photoexcited electrons were generated in the LUMO energy level and involved in the oxygen reduction reaction, finally resulting in an increasing current and a decreasing overpotential. According to the current signal, simple and efficient detection of CA15-3 was achieved.

The increasing demands for portable, wearable, and implantable sensing devices have stimulated growing interest in innovative electrode materials. In this work, we have demonstrated that printing a conductive ink formulated by blending three-dimensional (3D) porous graphene-carbon nanotube (CNT) assembly with ionic liquid (IL) on two-dimensional (2D) graphene paper (GP), leads to a freestanding GP supported graphene-CNT-IL nanocomposite (graphene-CNT-IL/GP). The incorporation of highly conductive CNTs into graphene assembly effectively increases its surface area and improves its electrical and mechanical properties. The graphene-CNT-IL/GP, as freestanding and flexible substrates, allows for efficient loading of PtAu alloy nanoparticles by means of ultrasonic-electrochemical deposition. Owing to the synergistic effect of PtAu alloy nanoparticles, 3D porous graphene-CNT scaffold, IL binder and 2D flexible GP substrate, the resultant lightweight nanohybrid paper electrode exhibits excellent sensing performances in nonenzymatic electrochemical detection of glucose in terms of sensitivity, selectivity, reproducibility and mechanical properties.

Here we show that a simple paper-based electrochemical sensor, fabricated by paper folding, is able to detect a 30-base nucleotide sequence characteristic of DNA from the hepatitis B virus (HBV) with a detection limit of 85 pM. This device is based on design principles we have reported previously for detecting proteins via a metalloimmunoassay. It has four desirable attributes. First, its design combines simple origami (paper folding) assembly, the open structure of a hollow-channel paper analytical device to accommodate micrometer-scale particles, and a convenient slip layer for timing incubation steps. Second, two stages of amplification are achieved: silver nanoparticle labels provide a maximum amplification factor of 250 000 and magnetic microbeads, which are mobile solid-phase supports for the capture probes, are concentrated at a detection electrode and provide an additional ∼25-fold amplification. Third, there are no enzymes or antibodies used in the assay, thereby increasing its speed, stability, and robustness. Fourth, only a single sample incubation step is required before detection is initiated.

Recycling hazardous wastes to produce value-added products is becoming essential for the sustainable progress of our society. Herein, highly porous carbon (1625 m2/g–1) is synthesized using waste tires as the precursor and used as supercapacitor electrode. The narrow pore size distribution (PSD) and high surface area led to a good charge storage capacity, especially when used as a three-dimensional nanoscaffold to polymerize polyaniline (PANI/TC). The composite film was highly flexible, conductive and exhibited a capacitance of 480 F/g–1 at 1 mV/s–1 with excellent capacitance retention up to 98% after 10,000 charge/discharge cycles. The high capacitance and long cycle life were ascribed to the short diffusional paths, uniform PANI coating and tight confinement of the PANI in the inner pores of the tire-derived carbon via - interactions, which minimized the degradation of the PANI upon cycling. Here, we anticipate that the same strategy can be applied to deposit other pseudocapacitive materials with low-cost TC to achieve even higher electrochemical performance and longer cycle life, a key challenge for redox active polymers.

The integration of paper with an electrochemical device has attracted growing attention for point-of-care testing, where it is of great importance to fabricate electrodes on paper in a low-cost, easy and versatile way. In this work, we report a simple strategy for directly writing electrodes on paper using a pressure-assisted ball pen to form a paper-based electrochemical device (PED). This method is demonstrated to be capable of fabricating electrodes on paper with good electrical conductivity and electrochemical performance, holding great potential to be employed in point-of-care applications, such as in human health diagnostics and food safety detection. As examples, the PEDs fabricated using the developed method are applied for detection of glucose in artificial urine and melamine in sample solutions. Furthermore, our developed strategy is also extended to fabricate PEDs with multi-electrode arrays and write electrodes on non-planar surfaces (e.g., paper cup, human skin), indicating the potential application of our method in other fields, such as fabricating biosensors, paper electronics etc.

In this paper, a cellulose-based Electro-Active Paper (EAPap) energy scavenging transducer is presented. Cellulose is proven as a smart material, and exhibits piezoelectric effect. Specimens were prepared by coating gold electrodes on both sides of cellulose film. The fabricated specimens were tested by a base excited aluminum cantilever beam at resonant frequency. Different tests were performed with single and multiple parallel connected electrodes coated on the cellulose film. A maximum of 131 mV output voltage was measured, when three electrodes were connected in parallel. It was observed that voltage output increases significantly with the area of electrodes. From these results, it can be concluded that the piezoelectricity of cellulose-based EAPap can be used in energy transduction application.

A novel paper-based analytical device (PAD) coupled with a silver nanoparticle-modified boron-doped diamond (AgNP/BDD) electrode was first developed as a cholesterol sensor. The AgNP/BDD electrode was used as working electrode after modification by AgNPs using an electrodeposition method. Wax printing was used to define the hydrophilic and hydrophobic areas on filter paper, and then counter and reference electrodes were fabricated on the hydrophilic area by screen-printing in house. For the amperometric detection, cholesterol and cholesterol oxidase (ChOx) were directly drop-cast onto the hydrophilic area, and H2O2 produced from the enzymatic reaction was monitored. The fabricated device demonstrated a good linearity (0.39 mg dL(-1) to 270.69 mg dL(-1)), low detection limit (0.25 mg dL(-1)), and high sensitivity (49.61 μA mM(-1) cm(-2)). The precision value for ten replicates was 3.76% RSD for 1 mM H2O2. In addition, this biosensor exhibited very high selectivity for cholesterol detection and excellent recoveries for bovine serum analysis (in the range of 99.6-100.8%). The results showed that this new sensing platform will be an alternative tool for cholesterol detection in routine diagnosis and offers the advantages of low sample/reagent consumption, low cost, portability, and short analysis time.

Paper-based analytical devices (PAD) emerge in the scientific community since 2007 as low-cost, wearable and disposable devices for point-of-care diagnostic due to the widespread availability, long-time knowledge and easy manufacturing of cellulose. Rapidly, electrodes were introduced in PAD for electrochemical measurements. Together with biological components, a new generation of electrochemical biosensors was born. This review aims to take an inventory of existing electrochemical paper-based biosensors and biofuel cells and to identify, at the light of newly acquired data, suitable methodologies and crucial parameters in this field. Paper selection, electrode material, hydrophobization of cellulose, dedicated electrochemical devices and electrode configuration in biosensors and biofuel cells will be discussed.

Herein, an origami multiplexed enzyme-free electrochemical (EC) immunodevice is developed for the first time. Typically, ZnO nanorods (ZNRs) modified reduced graphene oxide (rGO)-paper electrode is used as a sensor platform, in which rGO improves the electronic transmission rate and ZNRs provide abundant sites for capture probes binding. Furthermore, by combining the large surface area of rGO and high catalytic activity of bovine serum protein (BSA)-stabilized silver nanoparticles (Ag@BSA) toward H 2 O 2 reduction, rGO/Ag@BSA composites can be used as an excellent signal labels. The current signal is generated from the reduction of H 2 O 2 and further amplified by a subsequent signal labels-promoted deposition of silver. Under optimal conditions, the proposed immunoassays exhibit excellent precision, high sensitivity and a wide linear range of 0.002–120 mIU mL −1 for human chorionic gonadotropin, 0.001–110 ng mL −1 for prostate-specific antigen, and 0.001–100 ng mL −1 for carcinoembryonic antigen. The results for real sample analysis demonstrate that the newly constructed immunosensor arrays provide a simple and cost-effective method for clinical applications.

Poly(ethyleneimine)–TiO2–anthocyanin modified cellulose fiber sheets were prepared as a support material for dye-sensitized solar cells. The study is focused on the effects of different anthocyanins on the photo-induced changes and contact relaxation of the surface AC-conductivity of the papers. The anthocyanins were extracted from purple cabbage, beet-root, plum peel, red vine and red currant juice. The results showed that there were pronounced contact relaxation effects at the interfaces between alumina electrode and the papers, which were further affected by the presence of anthocyanins. The electrode effects are mainly manifested by a decrease in conductance, which falls by about 30 % from its initial value about 400 min after the beginning of the experiment carried out in the dark. The illumination of the samples induces an increase in the magnitude of the observed changes in conductance but does not affect the nature of the relaxation processes. By estimating the temperature coefficients of conductivity of the papers and the changes in temperature during the illumination of the samples, we succeeded to separate the effects of heating from the total effects of illumination on the conductance and susceptance of the papers.

Conductive tattoo nanosheets are fabricated on top of decal transfer paper and transferred on target surfaces as temporary transfer tattoos. Circuits are patterned with ink-jet printing. Tattoo nanosheets are envisioned as unperceivable human-device interfaces because of conformal adhesion to complex surfaces including skin. They are tested as dry electrodes for surface electromyography (sEMG), which permits the control of a robotic hand.

The electrochemical oxidation of phenol in synthetic wastewater and paper mill wastewater catalyzed by metal ion supported on cation exchange resin in suspended bed electrolytic reactor with graphite electrode has been investigated. The catalyst was characterized by SEM and XPS spectra and the effects of pH, the different metal ion and NaCl on the efficiency of the electrochemical oxidation phenol process were also studied. It was found that the catalyst containing Fe3+ had the highest electrochemical catalytic activity for the electrochemical oxidation of phenol. When the initial concentration of phenol was 200 ppm, up to 90% chemical oxygen demand (COD) removal was obtained in 10 min. When the catalyst containing Fe3+ was used to the paper mill wastewater, it still showed high efficiency. The COD removal could get to 75% in 60 min.

A simple, low-cost, and sensitive 3D microfluidic origami electrochemiluminescence aptamer-device was developed based on a novel gold nanoparticle modified porous paper working electrode for point-of-care diagnosis.

Paper‐based materials are emerging as a new category of advanced electrodes for flexible energy storage devices, including supercapacitors, Li‐ion batteries, Li‐S batteries, Li‐oxygen batteries. This review summarizes recent advances in the synthesis of paper‐based electrodes, including paper‐supported electrodes and paper‐like electrodes. Their structural features, electrochemical performances and implementation as electrodes for flexible energy storage devices including supercapacitors and batteries are highlighted and compared. Finally, we also discuss the challenges and opportunity of paper‐based electrodes and energy storage devices.

This paper describes the design and fabrication of ion-sensing electrochemical paper-based analytical devices (EPADs) in which a miniaturized paper reference electrode is integrated with a small ion-selective paper electrode (ISPE) for potentiometric measurements. Ion-sensing EPADs use printed wax barriers to define electrochemical sample and reference zones. Single-layer EPADs for sensing of chloride ions include wax-defined sample and reference zones that each incorporate a Ag/AgCl electrode. In EPADs developed for other electrolytes (potassium, sodium, and calcium ions), a PVC-based ion-selective membrane is added to separate the sample zone from a paper indicator electrode. After the addition of a small volume (less than 10 μL) of sample and reference solutions to different zones, ion-sensing EPADs exhibit a linear response, over 3 orders of magnitude, in ranges of electrolyte concentrations that are relevant to a variety of applications, with a slope close to the theoretical value (59.2/z mV). Ion-selective EPADs provide a portable, inexpensive, and disposable way of measuring concentrations of electrolyte ions in aqueous solutions.

Mechanical abrasion is an extremely simple, rapid, and low-cost method for deposition of carbon-based materials onto a substrate. However, the method is limited in throughput, precision, and surface compatibility for drawing conductive pathways. Selective patterning of surfaces using laser-etching can facilitate substantial improvements to address these current limitations for the abrasive deposition of carbon-based materials. This study demonstrates the successful on-demand fabrication of fully-drawn chemical sensors on a wide variety of substrates (e.g., weighing paper, polymethyl methacrylate, silicon, and adhesive tape) using single-walled carbon nanotubes (SWCNTs) as sensing materials and graphite as electrodes. Mechanical mixing of SWCNTs with solid or liquid selectors yields sensors that can detect and discriminate parts-per-million (ppm) quantities of various nitrogen-containing vapors (pyridine, aniline, triethylamine)., United States. Army Research Office. Institute for Soldier Nanotechnologies, United States. Defense Advanced Research Projects Agency, National Institutes of Health (U.S.) (Ruth L. Kirschstein National Research Service Award F32CA157197), National Cancer Institute (U.S.)

A novel paper working electrode with Pt nanospheres grown in it (Pt-PWE) was first used as a sensor platform and then cancer cells were immobilized on the Pt-PWE (high affinity binding with aptamers). This electrode was first designed to achieve the in situ and real-time determination of H2O2 released from cancer cells to obtain an accurate determination.

We report the memory device on paper by means of an all-printing approach. Using a sequence of inkjet and screen-printing techniques, a simple metal–insulator–metal device structure is fabricated on paper as a resistive random access memory with a potential to reach gigabyte capacities on an A4 paper. The printed-paper-based memory devices (PPMDs) exhibit reproducible switching endurance, reliable retention, tunable memory window, and the capability to operate under extreme bending conditions. In addition, the PBMD can be labeled on electronics or living objects for multifunctional, wearable, on-skin, and biocompatible applications. The disposability and the high-security data storage of the paper-based memory are also demonstrated to show the ease of data handling, which are not achievable for regular silicon-based electronic devices. We envision that the PPMDs manufactured by this cost-effective and time-efficient all-printing approach would be a key electronic component to fully activate a paper-based circuit and can be directly implemented in medical biosensors, multifunctional devices, and self-powered systems.

We report a new type of paper analytical device that provides quantitative electrochemical output and detects concentrations as low as 767 fM. The model analyte is labeled with silver nanoparticles (AgNPs), which provide 250 000-fold amplification. AgNPs eliminate the need for enzymatic amplification, thereby improving device stability and response time. The use of magnetic beads to preconcentrate the AgNPs at the detection electrode further improves sensitivity. Response time is improved by incorporation of a hollow channel, which increases the flow rate in the device by a factor of 7 and facilitates the use of magnetic beads. A key reaction necessary for label detection is made possible by the presence of a slip layer, a fluidic switch that can be actuated by manually slipping a piece of paper. The design of the device is versatile and should be useful for detection of proteins, nucleic acids, and microbes.

A novel electrochemical lab-on-paper cyto-device (ELPCD) was fabricated to demonstrate sensitive and specific cancer cell detection as well as in-situ monitoring of multi-glycans on living cancer cells. In this ELPCD, aptamers modified three-dimensional macroporous Au-paper electrode (Au-PE) was employed as the working electrode for specific and efficient cancer cell capture. Using a sandwich format, sensitive and reproducible cell detection was achieved in this ELPCD on the basis of the electrochemical signal amplification of the Au-PE and the horseradish peroxidase-lectin electrochemical probe. The ELPCD displayed excellent analytical performance for the detection of four K562 cells with a wide linear calibration range from 550 to 2.0×10(7) cells mL(-1). Then, this ELPCD was successfully applied to determine cell-surface multi-glycans in parallel and in-situ monitor multi-glycans expression on living cells in response to drug treatment through in-electrode 3D cell culture. The proposed method provides promising application in decipherment of the glycomic codes as well as clinical diagnosis and treatment in early process of cancer.

A novel approach to monitor Li levels in blood in decentralized (out of the lab) settings is presented. The approach uses a potentiometric cell fully made with filter paper as a support. Electrodes were built using carbon nanotubes ink to create a conductive path and a suitable polymeric membrane. Solid-state ion-selective electrodes for Li and a reference electrode were built and optimized. The results obtained on real samples of serum and whole blood are comparable with those obtained by conventional standard approaches. This platform shows an outstanding performance for the direct, fast and low-cost monitoring of Li levels in blood.

We demonstrate a flexible paper-based biofuel cell using porous carbon inks for high power output. The power density of the fabricated biofuel cell reached 0.12 mW cm(-2) (at 0.4 V), which is the highest output power reported to date, to the best of our knowledge.

Active, paper-based, microfluidic chips driven by electrowetting are fabricated and demonstrated for reagent transport and mixing. Instead of using the passive capillary force on the pulp to actuate a flow of a liquid, a group of digital drops are transported along programmed trajectories above the electrodes printed on low-cost paper, which should allow point-of-care production and diagnostic activities in the future.

This paper describes the development of a referenced Electrochemical Paper-based Analytical Device (rEPAD) comprising a sample zone, a reference zone, and a connecting microfluidic channel that includes a central contact zone. We demonstrated that the rEPADs provide a simple system for direct and accurate voltammetric measurements that are referenced by an electrode with a constant, well-defined potential. The performance of the rEPADs is comparable to commercial electrochemical cells, and the layout can be easily integrated into systems that permit multiplexed analysis and pipette-free sampling. The cost of this portable device is sufficiently low that it could be for single-use, disposable applications, and its method of fabrication is compatible with that used for other paper-based systems.

This work presents a simple, low cost method for creating microelectrodes for electrochemical paper-based analytical devices (ePADs). The microelectrodes were constructed by backfilling small holes made in polyester sheets using a CO2 laser etching system. To make electrical connections, the working electrodes were combined with silver screen-printed paper in a sandwich type two-electrode configuration. The devices were characterized using linear sweep voltammetry, and the results are in good agreement with theoretical predictions for electrode size and shape. As a proof-of-concept, cysteine was measured using cobalt phthalocyanine as a redox mediator. The rate constant (k(obs)) for the chemical reaction between cysteine and the redox mediator was obtained by chronoamperometry and found to be on the order of 10(5) s(-1) M(-1). Using a microelectrode array, it was possible to reach a limit of detection of 4.8 μM for cysteine. The results show that carbon paste microelectrodes can be easily integrated with paper-based analytical devices.

In this study, a low-cost and robust impedimetric immunosensor based on gold nanoparticles modified free-standing graphene paper electrode for rapid and sensitive detection of Escherichia coli O157:H7 (E. coli O157:H7) was developed. Graphene paper was prepared by chemical reduction of graphene oxide paper obtained from vacuum filtration method. Scanning electron microscope, Raman spectroscopy and X-ray diffraction techniques were employed to investigate the surface morphology and crystal structure of the prepared graphene paper. The gold nanoparticles were grown on the surface of graphene paper electrode by one-step electrodeposition technique. The immobilization of anti-E. coli O157:H7 antibodies on paper electrode were performed via biotin-streptavidin system. Electrochemical impedance spectroscopy was used to detect E. coli O157:H7 captured on the paper electrode. Results show that the developed paper immunosensor possesses greatly enhanced sensing performance, such as wide linear range (1.5 × 10(2)-1.5 × 10(7) cfu mL(-1)), low detection limit (1.5 × 10(2) cfu mL(-1)), and excellent specificity. Furthermore, flexible test demonstrate the graphene paper based sensing device has high tolerability to mechanical stress. The strategy of structurally integrating metal nanomaterials, graphene paper, and biorecognition molecules would provide new insight into design of flexible immunosensors for routine sensing applications.

Electrochemical paper-based analytical devices (ePADs) with integrated plasma isolation for determination of glucose from whole blood samples have been developed. A dumbbell shaped ePAD containing two blood separation zones (VF2 membranes) with a middle detection zone was fabricated using the wax dipping method. The dumbbell shaped device was designed to separate plasma while generating homogeneous flow to the middle detection zone of the ePAD. The proposed ePADs work with whole blood samples with 24-60% hematocrit without dilution, and the plasma was completely separated within 4 min. Glucose in isolated plasma separated was detected using glucose oxidase immobilized on the middle of the paper device. The hydrogen peroxide generated from the reaction between glucose and the enzyme pass through to a Prussian blue modified screen printed electrode (PB-SPEs). The currents measured using chronoamperometry at the optimal detection potential for H2O2 (-0.1 V versus Ag/AgCl reference electrode) were proportional to glucose concentrations in the whole blood. The linear range for glucose assay was in the range 0-33.1 mM (r(2)=0.987). The coefficients of variation (CVs) of currents were 6.5%, 9.0% and 8.0% when assay whole blood sample containing glucose concentration at 3.4, 6.3, and 15.6mM, respectively. Because each sample displayed intra-individual variation of electrochemical signal, glucose assay in whole blood samples were measured using the standard addition method. Results demonstrate that the ePAD glucose assay was not significantly different from the spectrophotometric method (p=0.376, paired sample t-test, n=10).

In this work, a photoelectrochemical (PEC) method was introduced into a microfluidic paper-based analytical device (μ-PAD), and thus, a truly low-cost, simple, portable, and disposable microfluidic PEC origami device (μ-PECOD) with an internal chemiluminescence light source and external digital multimeter (DMM) was demonstrated. The PEC responses of this μ-PECOD were investigated, and the enhancements of photocurrents in μ-PECOD were observed under both external and internal light sources compared with that on a traditional flat electrode counterpart. As a further amplification of the generated photocurrents, an all-solid-state paper supercapacitor was constructed and integrated into the μ-PECOD to collect and store the generated photocurrents. The stored electrical energy could be released instantaneously through the DMM to obtain an amplified (∼13-fold) and DMM-detectable current as well as a higher sensitivity than the direct photocurrent measurement, allowing the expensive and sophisticated electrochemical workstation or lock-in amplifier to be abandoned. As a model, sandwich adenosine triphosphate (ATP)-binding aptamers were taken as molecular reorganization elements on this μ-PECOD for the sensitive determination of ATP in human serum samples in the linear range from 1.0 pM to 1.0 nM with a detection limit of 0.2 pM. The specificity, reproducibility, and stability of this μ-PECOD were also investigated.

Well-separated RGO sheets decorated with MnO2 nanoparticles facilitate easy access of the electrolyte ions to the high surface area of the paper electrode, enabling the fabrication of a thicker electrode with heavier areal mass and higher areal capacitance (up to 897 mF cm(-2) ). The electrochemical performance of the bent asymmetric device with a total active mass of 15 mg remains similar to the one in the flat configuration, demonstrating good mechanical robustness of the device.