PPy Materials Research Articles

Zinc Oxide/Polypyrrole particle-decorated rod structure for NO2 detection at low temperature

In this study, Zinc oxide (ZnO) nanoparticles with a size of about 50 - 70 nm were green-synthesized using tea leaves and ZnO/Polypyrrole (ZnO/Ppy) nanocomposites were obtained by ultrasonic-assisted chemical polymerization method using pyrrole monomer and the nanoparticles. The characterization of the materials is conducted using several analytical techniques, including Field Emission Scanning Electron Microscopy (FESEM) and X-Ray Diffraction (XRD) and Ultraviolet visible spectrum (UV-Vis). The synthesized PPy material exhibits have a rod-shaped structure, diameter ranging from 100 to 200 nm. The ZnO/PPy nanocomposite system, consisting of PPy rods surrounded by ZnO particles. The gas sensing characteristics of the materials have also been investigated by measuring their sensitivity, response time, and stability to NO2 at low temperature and different humidity. Notably, the material exhibits considerable sensitivity to NO2 gas at low temperatures and the parameters related to response and recovery times are relatively rapid. Furthermore, a potential gas-sensing mechanism based on changes in the width of the depletion region is proposed.

Highly Wrinkled Porous Polypyrrole for the Enhancement of the Performance of an Fe2S3-Fe2O3/poly-O-amino Benzenethiol Supercapacitor from a Basic Medium

In this study, O-amino benzenethiol (OABT) was oxidized in one pot using Fe(NO3)3 to produce a novel Fe2S3-Fe2O3/poly O-amino benzenethiol (POABT), which showed a highly uniform morphology. At the same time, from SEM analysis, highly wrinkled porous polypyrrole (Ppy) and porous ball-like POABT structures prepared from the K2S2O8 route were evidenced by SEM and TEM analyses. A nanocomposite pseudo-supercapacitor (SC) was fabricated using Fe2S3-Fe2O3/POABT, and its performance was tested with and without incorporating Ppy in the paste. The results indicate that Ppy significantly increased the specific capacitance (CS) values, indicating an enhancement in charge storage. At a current density of 0.2 A/g, the CS values were 44 F/g and 161 F/g for the paste without and with Ppy, respectively. Additionally, the E was calculated, and the incorporation of Ppy resulted in a significant increase in E, reaching 30 W.h.kg−1; this was significantly higher than the value of 8.18 W.h.kg−1 observed without Ppy materials. This effect is likely due to the improved charge transfer facilitated by the presence of Ppy, as evidenced by the Nyquist plot, where the Rct values were 1.1 Ω and 2.1 Ω with and without Ppy, respectively. Overall, the low cost and significant technical advantages of this capacitor make it a promising candidate for commercial applications.

In situ synthesis of label-free electrochemical aptasensor-based sandwich-like AuNPs/PPy/Ti3C2Tx for ultrasensitive detection of lead ions as hazardous pollutants in environmental fluids

The monitoring of hazardous pollutants in environmental fluids is one of main stretaegy in investigation of water and soil quality. Metal ions are one of main and dangerius materials in water sampels and one of the main causes of environmental problems. Therefore, many of environmental researchers focused on fabrication of highly sensitive sensor to ion hazardous pollutants environmental fluids. The encapsulation of 2D MXenes with other stable materials has proven to be an effective method for enhancing their stability and electrochemical properties. In this work, a sandwich-like nanocomposite structure, AuNPs/PPy/Ti3C2Tx, was designed and synthesized via a facile method of one-step layer-by-layer self-assembly. The morphology and structure of the prepared nanocomposites are characterized with various methods such as scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Ti3C2Tx as a substrate played a significant role in the synthesis and alignment of PPy and AuNPs growth. The nanocomposites have maximized the benefits of the inorganic AuNPs and organic PPy materials, enhancing their stability and electrochemical performance. Meanwhile, AuNPs have given the nanocomposite the ability to form covalent bonds with biomaterials via the Au–S bond. Thus, a novel electrochemical aptasensor was developed based on AuNPs/PPy/Ti3C2Tx for the sensitive and selective detection of Pb2+. It demonstrated a wide linear range from 5 × 10−14 to 1 × 10−8 M with a low LOD of 1 × 10−14 M (S/N = 3). Additionally, the developed aptasensor exhibited excellent selectivity and stability and successfully used to sensing of Pb2+ in environmental fluids such as NongFu Spring and tap water.

Electromagnetic Properties of Polypyrrole Metallic Magnetic Nanocomposites: First‐Principles Study

AbstractConductive polypyrrole (PPy) is an excellent polymer material for microwave absorption, which is vital for reducing electromagnetic interference (EMI) for electronic devices. To improve the microwave absorption capability and enhance the thermal stability and mechanical ductility of conductive PPy, metallic magnetic nanoparticles can be added to form PPy nanocomposites. In this paper, we present the first study to compute the electromagnetic properties of PPy nanocomposites based on the first principles method. It is discovered that (1) while doping can improve the microwave absorbing properties of PPy material, the absorption performance does not necessarily increase with the number of doping position; (2) conductivity and absorption coefficient increase significantly for the PPy nanocomposite compared with PPy. The dielectric loss is more than 2 at about 2 eV; (3) reflectivity and absorption coefficient decrease with the increase of PPy content in PPy/Co nanocomposite; (4) the average magnetic moment of the PPy nanocomposite is the same as that of pure nanoparticles, and this indicates that only nanoparticles generate magnetic loss for the nanocomposite.

Polypyrrole-Dopamine Nanofiber Light-Trapping Coating for Efficient Solar Vapor Generation.

Solar vapor generation (SVG) typically uses a solar absorbing material at the water-air interface to convert solar energy into heat for evaporation. However, the intrinsic solar absorption of the material determines the upper limit of the solar energy capture. By designing a light-trapping surface structure with open pores and channels, we can break this limit and further improve the absorption by enabling multiple reflections within the surface. Polypyrrole (PPy) is emerging as a promising solar thermal material. In this work, we propose an ultrasonic spray coating method to obtain a nanofiber light-trapping coating by copolymerization with dopamine (DA), which can be directly synthesized at room temperature rapidly (30 min). Due to its excellent wettability, this coating can transport water and can be directly coated on the thermal insulating layer, not requiring an additional water transport layer. This nanoscale coating significantly improves solar absorption at different incident angles across the full solar spectrum, achieving the highest solar-to-thermal conversion efficiency of 95.8% at 1.385 kg·m-2·h-1 under 1 sun. When applied on salt water, this solar evaporator achieves self-cleaning in the absence of solar irradiation. Moreover, the surface structure can be further tuned into granular/plane-fibrous/plane-granular structures by using different oxidants or surfactants, and their formation mechanisms are also proposed. This PPy-DA nanofiber coating shows great potential for SVG and other applications based on a PPy material, especially for those requiring a certain surface morphology.

Effects of Interchain Crosslinking By Alkyl Dihalides on the Ion Insertion Mechanism of Polypyrrole Thin Films

Conductive polymers (CPs) such as polypyrrole (PPY) and PEDOT can exhibit high charge storage capacities, high electronic conductivities, and tunable chemical and optical properties. CPs thus have a wide range of applications in electronic devices, including in organic electronics, sensors, and battery materials. The electrochemical properties of PPY in particular can be controlled to provide high electronic conductivity (up to 200 S/cm) and high redox activity (up to 500 F/g), making it an attractive material for device application. The electrochemical characteristics of PPY are commonly controlled by adjusting polymerization conditions, adding dopants, and forming composites with other polymers. A lesser studied phenomenon is the effect of nitrogen substituents on the electrochemical properties of PPY. In this work, we present an investigation into the charge-transfer mechanisms and electrochemical properties of nanoscale PPY films before and after interchain crosslinking with several different alkyl dihalides. Our investigation involves deposition and alkylation of PPY thin films followed with optical and electrochemical characterization via electrochemical quartz crystal microbalance and spectroscopic ellipsometry. Individual polymer chains in the PPY film are connected across adjacent nitrogens via an alkyl bridge, and the properties of the subsequent films are examined and compared to those of intrinsic PPY and other redox active materials. The results of our ongoing research give insight into new sub-classes of CPs with different redox properties and ion transfer mechanisms from intrinsic PPY. These novel PPY derivatives are low-cost, easy to synthesize, and show promise for application to sensors, ion exchange materials, and charge-storage devices.

Simultaneous Recognition of Dopamine and Uric Acid in the Presence of Ascorbic Acid via an Intercalated MXene/PPy Nanocomposite.

Two-dimensional (2D) MXenes have shown a great potential for chemical sensing due to their electric properties. In this work, a Ti3C2Tx/polypyrrole (MXene/PPy) nanocomposite has been synthesized and immobilized into a glassy carbon electrode to enable the simultaneous recognition of dopamine (DA) and uric acid (UA) under the interference of ascorbic acid (AA). The multilayer Ti3C2Tx MXene was prepared via the aqueous acid etching method and delaminated to a single layer nanosheet, benefiting the in-situ growth of PPy nanowires. The controllable preparation strategy and the compounding of PPy material remain great challenges for further practical application. A facile chemical oxidation method was proposed to regulate magnitude and density during the forming process of PPy nanowire, which promotes the conductivity and the electrochemical active site of this as-prepared nanomaterial. The MXene/PPy nanocomposite-modified electrode exhibited the selective determination of DA and UA in the presence of a high concentration of AA, as well as a wide linear range (DA: 12.5–125 μM, UA: 50–500 μM) and a low detection limit (DA: 0.37 μM, UA: 0.15 μM). More importantly, the simultaneous sensing for the co-existence of DA and UA was successfully achieved via the as-prepared sensor.

Organic Surfactant Assisted Polypyrrole Materials as Effective Chemiresistive Gas Sensors for VOCs and Toxic Gas Detection

Surfactant assisted PPy materials are explored as efficient gas sensors for VOCs and toxic gases in the present work. Polypyrrole nanostructures were prepared by chemical oxidative polymerization using various sulfonic acids as surfactants between 0-5 °C. The effect of sulfonyl group on PPy was confirmed by FT-IR spectrum analysis. Doping of sulfonic acid has a strong effect on morphology of polymer blends which displayed the amorphous, globular, cauliflower, flakes and compact sheet like structures observed in the surface morphology. The conductivity of doped PPy observed to be dependent on the nature of dopant and its doping level. The electrical conductivity was observed to enhance by an order in magnitude on the addition of organic surfactants from 0.1 to 2.0 M. The pristine PPy shows high % response of 93% and 70% only for NH3 and Cl2 respectively. But different surfactant doped PPy were found to be highly sensitive for most of the VOCs and toxic gases which emerged as efficient sensor materials for fast response and recovery at the lowest level of 5 ppm.

All-polymer ultrathin flexible supercapacitors for electronic skin

Ultrathin flexible supercapacitors (UF-SCs) are highly desired for powering electronic skin devices. Most of current UF-SCs require electrochemically inactive substrates and binders to load electro-active materials, which limit the volumetric capacitance and stability of these UF-SCs. Herein, we report an all-polymer UF-SC based on conductive polypyrrole (PPy) film, which is constructed by the dynamic network formed by rigid PPy (~90 wt%) and soft polyethylene glycol (PEG, only 10 wt%) through supramolecular interactions. The network structure can effectively dissipate the destructive energy during mechanical or electrochemical deformation, making the PPy film strong and robust; and also helps to maximize the utilization of PPy, enabling the PPy film better electric conductivity and electrochemical capacitance than conventional PPy materials. After systematic optimization, we found the PEG600-PPy as the optimal electrode material, which can serve as electroactive material, current collector, and mechanical support simultaneously. Therefore, without using any substrate or current collector, these high-performance PEG600-PPy films can be directly used as electrodes for making all-polymer UF-SC. With high volumetric capacitance (547 F/cm3), outstanding mechanical and electrochemical stability, our all-polymer UF-SC (~80 μm in thickness, thinner than a piece of A4 paper) is a promising power device for electronic skin devices.

Metal-organic framework derived Co3O4/PPy bifunctional electrocatalysts for efficient overall water splitting

In this work, we report Co3O4@PPy hybrid structured electrode materials for overall water splitting. The as-synthesized Co3O4/PPy-120 samples present excellent electrocatalytic performances for OER and HER and long durability. It only requires an operating potential of 1.67 V to deliver a current density of 10 mA/cm2 with a remarkable durability for 28 h. The superior electrocatalytic performances mainly can be attributed to the unique heterostructures and the synergistic effects between PPy and Co3O4 electrode materials.

Synthesis and characterization of polypyrrole and its composites coatings on flexible surface and its antibacterial properties

The main motivation of this work was to develop a simple and efficient way to obtain polypyrrole–Ag, polypyrrole–Au, and unmodified polypyrrole layers on non-conducting, flexible surfaces as advanced antibacterial agents. We used filtering paper as a substrate for conducting polymer and its composite polymerization. The material was covered by polypyrrole, polypyrrole–Au, and polypyrrole–Ag composites during electroless (chemical) polymerization occurring at a boundary of two immiscible liquids. A presence of metals in deposited PPy films was confirmed by EDS analyses. It was proven that PPy–Ag nanocomposites deposited on the flexible substrate exhibit good antibacterial properties against both Gram-negative and Gram-positive bacteria. The antibacterial properties of PPy–Au, and non-modified PPy materials were not observed. Both, PPy and PPy–Au deposits revealed low cytotoxicity on THP-1 cells line used as reference human cells. PPy–Ag films exhibited higher toxicity on THP-1 cells line, but much weaker than toxicity toward pathogenic bacteria. SEM imagining showed changes in the morphology of the cells and their activation in contact with conducting materials. Cyclic voltammetry experiments showed that the proposed procedure leads to obtain solid materials in conducting state. It is also an easy way of fabrication of conducting polymers deposited on non-conducting surfaces. Obtained materials possess good antibacterial properties and low cytotoxicity, which opens the broad applicability of those materials. Composites placed on flexible substrates are suitable for modification of inert electrodes surfaces, e.g., for enhancement of their electro-catalytical properties.

Enhanced specific capacitance of a novel ternary polypyrrole incorporated with prussian blue and mesoporous carbon black for high performance supercapacitor applications

A facile ternary composite of polypyrrole (PPy), prussian blue (PB) and carbon black (CB), PPy-PB-CB is synthesized by oxidative polymerization of pyrrole and formation of PB on CB to achieve efficient electrode material for supercapacitor. The polymer composite is characterized structurally and morphologically; CV, GCD and EIS techniques are used to evaluate the capacitive behavior of the ternary composite. PPy-PB-CB electrode exhibits a specific capacitance of 163.7 F g−1 in neutral electrolyte, KCl which is superior to PPy, PPy-PB and PPy-CB electrode materials. Moreover, the ternary composite retains 98.35% of its initial capacitance even after 2000 cycles, exhibits high specific power, 10.78 kW kg−1 and high specific energy, 18.1 Wh kg−1. The excellent performance of the ternary polymer composite is attributed to the synergistic effect of high specific capacitance of pseudocapacitive electrodes, namely, PPy, and PB and better reversible nature of EDLC electrode, CB and its porosity.

Simultaneous Electrochemical Deposition of Cobalt Complex and Poly(pyrrole) Thin Films for Supercapacitor Electrodes

Supercapacitors are beneficial as energy storage devices and can obtain high capacitance values greater than conventional capacitors and high power densities compared to batteries. However, in order to improve upon the overall cost, energy density, and charge-discharge rates, the electrode material of supercapacitors needs to be fine-tuned with an inexpensive, high conducting source. We prepared a Co(III) complex and polypyrrole (PPy) composite thin films (CoN4-PPy) that was electrochemically deposited on the surface of a glassy carbon working electrode. Cyclic voltammetry studies indicate the superior performance of CoN4-PPy in charge storage in acidic electrolyte compared to alkaline and organic solutions. The CoN4-PPy material generated the highest amount of specific capacitance (up to 721.9 F/g) followed by Co salt and PPy (Co-PPy) material and PPy alone. Cyclic performance studies showed the excellent electrochemical stability of the CoN4-PPy film in the acidic medium. Simply electrochemically depositing an inexpensive Co(III) complex with a high electrically conducting polymer of PPy delivered a superior electrode material for supercapacitor applications. Therefore, the results indicate that novel thin films derived from Co(III) metal complex and PPy can store a large amount of energy and maintain high stability over many cycles, revealing its excellent potential in supercapacitor devices.

Synthesis and Electroresponse Activity of Porous Polypyrrole/Silica-Titania Core/Shell Nanoparticles.

Inverted conducting polymer/metal oxide core/shell structured pPPy/SiO2-TiO2 nanoparticles were prepared as electrorheological (ER) materials using sequential experimental methods. The core was synthesized via the low-temperature self-assembly of PPy and SiO2 materials, and the outer TiO2 shell was easily coated onto the core part using a sol-gel method and a titanium isopropoxide precursor. Sonication-mediated etching and redeposition were employed to etch out SiO2 portions from the core part to blend with TiO2 shells. Each step in nanoparticle synthesis involved morphological and physical changes to the surface area and porosity, with subsequent changes in the intrinsic properties of the materials. Specifically, the electrical conductivity and dielectric properties were successfully altered. The final pPPy/SiO2-TiO2 nanoparticle configuration was optimized for ER applications, offering low electrical conductivity, high dielectric properties, and increased dispersion stability. pPPy/SiO2-TiO2 nanoparticles exhibited 24.7- and 2.7-fold enhancements in ER performance compared to that of PPy-SiO2 and PPy-SiO2/TiO2 precursor nanoparticles, respectively. The versatile method proposed in this study for the synthesis of inverted conducting polymer/metal oxide core/shell nanoparticles shows great potential for the development of custom-designed ER materials.

CTAB-assisted microemulsion synthesis of unique 3D network nanostructured polypyrrole presenting significantly diverse capacitance performances in different electrolytes

In this work, the unique 3D network nanostructured polypyrrole (PPy) has been successfully synthesized in cetyltrimethylammonium bromide/butyl alcohol/hexane/water microemulsion system. The composition, crystalline characteristic and morphology of as-prepared PPy materials are characterized by Fourier transform infrared spectrometer, X-ray diffractometer and field emission scanning electron microscope. It is shown that as-prepared PPy materials possess unique 3D network nanostructure stacked by PPy nanospheres with an average diameter of 100 nm. Furthermore, the electrochemical performances of PPy based electrodes are investigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectrum in 1.0 M H2SO4, 1.0 M Na2SO4 and 1.0 M KCl electrolytes, respectively. At a current density of 1.0 A g−1, as-prepared PPy based electrode exhibits the highest specific capacitance (329.0 F g−1) in 1.0 M H2SO4 electrolyte, much higher than that in 1.0 M Na2SO4 (156.6 F g−1) or 1.0 M KCl (153.2 F g−1) electrolyte. However, the specific capacitance of PPy based electrode in 1.0 M H2SO4 electrolyte retains only 40.6% of the initial specific capacitance after 5000 continuous charge/discharge cycles and, interestingly, 83.9% and 81.3% in 1.0 M Na2SO4 and 1.0 M KCl electrolytes, respectively. It is reasonable that the process of deoxidation and reoxidation of PPy nanomaterials is accompanied by the intercalation and deintercalation of massive H3O+ in 1.0 M H2SO4 electrolyte, which might result in the collapsed structure of as-prepared PPy nanomaterials and the relative instability during the cycling process.

Polypyrrole composites with carbon materials for supercapacitors

Supercapacitors fill the gap between batteries and conventional solid state and electrolytic capacitors. Polypyrrole (PPy) is a very important electrode material for supercapacitors. However, the repeated volume changes usually damage PPy structure and result in PPy poor stability during a long-term charging/discharging process. PPy/carbon material composites were prepared to overcome the defects of pure PPy electrodes, and significant enhancement for the specific capacitance, charging/discharging rate and electrodes stability was demonstrated thereafter. The development of composite electrodes based on PPy and carbon materials is reviewed in this paper.

Facial Synthesis of Silver-incorporated Conductive Polypyrrole Submicron Spheres for Supercapacitors

Spherical silver-incorporated conductive polypyrrole (PPy) composite is successfully prepared via oxidative polymerization of pyrrole in an aqueous Ag+-containing solution in the presence of trisodium citrate. Citrate produces stable and charged micelles, thus tailoring the facial polymerization of the pyrrole. Monodispersed submicron spheres of silver/PPy composite are obtained by maintaining the molar ratio of citrate anion to silver cation at 3:1. Highly dispersed metallic Ag is uniformly incorporated in the PPy matrix, thus increasing the charge transfer ability of PPy materials. The as-prepared Ag/PPy material exhibits ideal capacitive behavior and has excellent cyclic stability. Charge-discharge measurements demonstrate a maximum specific capacitance of 315.8Fg−1 for the Ag/PPy electrode, which is much higher than that of a pure PPy electrode (153.2Fg−1). A high specific energy density of 43.9 Wh kg−1 can be achieved at 50W Kg−1 for PPy in the Ag/PPy electrode, and 30 Wh kg−1 remains at 500W Kg−1. The facially synthesized Ag/PPy composite possesses promising properties for use as an electrode material for supercapacitors.

Graphene oxide/polypyrrole composites for highly selective enrichment of U(vi) from aqueous solutions

Graphene oxide/polypyrrole (GO/PPy) composites were synthesized via a dielectric barrier discharge (DBD) plasma technique in nitrogen conditions, and characterized by scanning electron microscopy (SEM), Raman spectroscopy, thermal gravimetric analysis (TGA), Fourier transformed infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The sorption of U(VI) ions on GO/PPy composites from aqueous solutions was investigated as a function of contact time, pH, ionic strength and U(VI) initial concentrations. The sorption capacity of U(VI) on GO/PPy composites was much higher than those of U(VI) on GO, PPy and many other materials of today. The sorption of U(VI) on GO/PPy composites obeyed the Langmuir model, and was mainly attributed to surface complexation via the coordination of U(VI) ions with oxygen- and nitrogen-containing functional groups. The selectivity sorption of U(VI) ions on GO/PPy composites in the presence of other metal ions (i.e., Co(II), Ni(II), Cd(II), Sr(II), Zn(II)) indicated an overall preference for U(VI) ions. Moreover, the GO/PPy composites could be regenerated through the desorption of adsorbed U(VI) ions by using 1.0 M HCl solution, and cycling reused without an obvious decrease of sorption capacity. All these performances indicate that GO/PPy composites are suitable materials for the highly selective removal and preconcentration of U(VI) ions from aqueous solutions in environmental pollution management.

Polypyrrole coated carbon nanotubes for supercapacitor devices with enhanced electrochemical performance

Polypyrrole (PPy) electrodes for electrochemical supercapacitors (ES) are prepared using amaranth as a new redox-active anionic dopant for chemical polymerization of PPy. The use of amaranth allows excellent electrochemical performance of electrodes with high mass loading and high PPy to current collector mass ratio. The specific capacitance of 4.2 F cm−2 is achieved at a scan rate of 2 mV s−1. The analysis of electrochemical testing results provides an insight into the influence of the chemical structure of amaranth on microstructure, electrochemical properties and cycling stability of PPy. New method is introduced for the fabrication of PPy coated multiwalled carbon nanotubes (MWCNT). The use of amaranth allows fine microstructure of PPy coatings formed on MWCNT, which are well dispersed in the presence of pyrocatechol violet dispersant. The use of PPy coated MWCNT allows significant improvement in capacitance retention at high charge–discharge rates, compared to pure PPy material, and good cycling stability of individual electrodes and ES cells. The ES cells, based on PPy show specific capacitance of 1.3–1.6 F cm−2 at discharge current densities of 1–33 mA cm−2.

Polypyrrole Nanotube Embedded Reduced Graphene Oxide Transducer for Field-Effect Transistor-Type H2O2 Biosensor

We report a rapid-response and high-sensitivity sensor with specificity toward H2O2 based on a liquid-ion-gated field-effect transistor (FET) using graphene-polypyrrole (PPy) nanotube (NT) composites as the conductive channel. The rGO, PPy, NTs, and nanocomposite materials were characterized using Raman spectroscopy, Fourier transform-infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). On the basis of these results, a well-organized structure is successfully prepared owing to the specific interactions between the PPy NTs and the rGO sheet. Reliable electrical contacts were developed between the rGO/PPy NTs and the microelectrodes, which remained stable when exposed to the liquid-phase analyte. Liquid-ion-gated FETs composed of these graphene nanocomposites exhibited hole-transport behavior with conductivities higher than those of rGO sheets or PPy NTs. This implies an interaction between the PPy NTs and the rGO layers, which is explained in terms of the PPy NTs forming a bridge between the rGO layers. The FET sensor provided a rapid response in real time and high sensitivity toward H2O2 with a limit of detection of 100 pM. The FET-type biosensing geometry was also highly reproducible and stable in air. Furthermore, the liquid-gated FET-type sensor exhibited specificity toward H2O2 in a mixed solution containing compounds found in biological fluids.