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Research on flexible biosensors is mostly focused on their use in obtaining information on physical signals (such as temperature, heart rate, pH, and intraocular pressure). Consequently, there are hardly any studies on using flexible electronics for detecting biomolecules and biomarkers that cause diseases. In this study, we propose a flexible, three-dimensional carbon nanoweb (3DCNW)-based aptamer sensor to detect the platelet-induced growth factor (PDGF), which is an oncogenic biomarker. As a template for the 3D structure, poly(acrylonitrile) (PAN) nanowebs were synthesized using a facile electrospinning process. The PAN nanowebs were then subjected to chemical vapor deposition with copper powder. This was followed by Cu etching to generate carbon protrusions on the web surface. As an active site, PDGF-B binding aptamer was introduced on the 3DCNW surface to form biosensor electrodes. The 3DCNW-based aptasensor exhibited excellent sensitivity (down to 1.78 fM), with high selectivity, reversibility, and stability to PDGF-BB.

Field-effect transistor (FET) devices based on conductive nanomaterials have been used to develop biosensors. However, development of FET-based biosensors that allow efficient stability, especially in the gas phase, for obtaining reliable and reproducible responses remains a challenge. In this study, we developed a nanodisc (ND)-functionalized bioelectronic nose (NBN) based on a nickel (Ni)-decorated carboxylated polypyrrole nanoparticle (cPPyNP)-FET that offers the detection of liquid and gaseous cadaverine (CV). The TAAR13c, specifically binding to CV, which is an indicator of food spoilage, was successfully constructed in NDs. The NBN was fabricated by the oriented assembly of TAAR13c-embedded NDs (T13NDs) onto the transistor with Ni/cPPyNPs. The NBN showed high performance in selectivity and sensitivity for the detection of CV, with excellent stability in both aqueous and gas phases. Moreover, the NBN allowed efficient measurement of corrupted real-food samples. It demonstrates the ND-based device can allow the practical biosensor that provides high stability in the gas phase.

In this work, a high-performance sensor capable of effectively detecting nerve gas, a type of chemical warfare agent, was realized by conductive paper with polyaniline (PANI) nanofiber and graphene...

Metal–organic framework (MOF)-derived electroactive materials have drawn great attention due to their diverse design and high electrochemical activity. Herein, a unique hybrid structure consisting of Ni–Co layered double hydroxides (LDHs) and hollow carbon spheres (HCSs) is first synthesized using HCS@ZIF-67 as a precursor. Particularly, when the ZIF-67 content in the precursor is optimized, a novel hybrid with a hollow-in-hollow structure can be obtained by distributing ZIF-67-derived hollow Ni–Co LDHs on a HCS shell. Owing to their distinctive structural characteristics, the as-prepared architectures deliver a high specific capacity (156.4 mA h g−1 at 5 A g−1) and excellent cycle stability (73.4% capacity retention after 10 000 cycles). Notably, during the charge storage process, the dual hollow system of the composite effectively decreases the ion diffusion path, resulting in drastically improved rate performance (70% retention of its highest capacity at 80 A g−1). Furthermore, an all-solid-state hybrid supercapacitor is assembled using the as-fabricated hybrid as the positive material and mesoporous plasma-reduced graphene oxide as the negative material, and exhibits a maximum energy density of 34.5 W h kg−1 and a peak power density of 55 kW kg−1.

We report a facile approach for producing highly omnidirectional and frequency tunable antennas based on multilayer graphene/multi-walled carbon nanotube (MG/MWNTs) electrodes. The MG sheets are obtained by ball milling graphite, followed by sonication. Monopole patch antennas are prepared by screen printing the MG/MWNTs paste onto a polymer substrate. The resulting antennas show excellent performance due to the bridge effect of the MWNTs between well-dispersed adjacent MG layers, which increases the contact area between MG sheets along the horizontal and vertical axes. The antennas formed from the MG/MWNTs exhibit smaller return losses than the antennas formed from pristine graphite, as well as high radiation efficiency (∼44.9%). Moreover, the MG/MWNTs antennas require a relatively small quantity, which leads to low production costs. In addition, the dimensions of the antennas can be simply adjusted by controlling the screen printing mask or cutting with scissors to achieve frequency tunability. These results demonstrate the potential of these MG/MWNTs antennas for applications in wireless communications for ubiquitous sensor networks.

In this work, we report a facile way to control crystalline structures of polyketone (PK) films by combining plasma surface treatment with chemical vapor deposition (CVD) technique. The crystalline structure of PKs grown on plasma-treated graphene and the resulting thermal and mechanical properties were systematically discussed. Every graphene sheet used in this work was produced by CVD method and the production of PKs having different crystallinity were performed on the O2- and N2-doped graphene sheets. It was evident that the CVD-grown graphene sheets acted as the nucleating agents for promoting the crystallization of β-form PK, while suppressing the growth of α-form PK crystals. Regardless of the increase in surface roughness of graphene, surface functionality of the CVD-grown graphene was found to be an important factor in determining the crystalline structure of PK. N2 plasma treatment of the CVD-grown graphene promoted growth of the β-form PK, whereas the O2 plasma treatment of CVD graphene led to transformation of the unoriented β-form PK into the oriented α-form PK. Thus, the resulting thermal and mechanical properties of the PKs were highly dependent on the surface functionality of the CVD graphene. The method of controlling crystalline structure of the PKs suggested in this study, is expected to be very effective in realizing the PK with good processability, heat resistance and mechanical properties.

Inverted-structure perovskite solar cells (PSCs), with low-temperature processed poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) and perovskite-passivating phenyl–C61–butyric acid methyl ester (PCBM) employed as charge transport layers, have great potential as efficient, flexible, and hysteresis-free solar cells. However, PEDOT:PSS processed from an aqueous solution has a hygroscopic nature, and can degrade the ambient stability of moisture-vulnerable perovskite electronics. Furthermore, excess insulating PSS in the PEDOT:PSS complex can deteriorate the hole extraction and photovoltaic performance of the solar cell. In this work, polyaniline doped with camphorsulfonic acid (PANI-CSA) is introduced as a hole transport layer (HTL) to promote hole extraction ability and improve the efficiency and stability of inverted PSCs. The device fabricated with PANI-CSA exhibited superior photovoltaic performance, with a maximum efficiency of 15.42%, compared to 14.11% efficiency for the device fabricated with PEDOT:PSS. Most notably, the stability of the device fabricated with PANI-CSA was greatly improved due to a stable HTL/perovskite interface against exposure to ambient moisture.

Hydrogen sulfide (H2S) is one of the most plentiful toxic gases in a real-life and causes a collapse of the nervous system and a disturbance of the cellular respiration. Therefore, highly sensitive and selective H2S gas sensor systems are becoming increasingly important in environmental monitoring and safety. In this report, we suggest the facile synthesis method of the Fe2O3 particles uniformly decorated on carbon nanotubes (Fe2O3@CNT) to detect H2S gas using oxidative co-polymerization (pyrrole and 3-carboxylated pyrrole) and heat treatment. The as prepared Fe2O3@CNT-based sensor electrode is highly sensitive (as low as 1 ppm), selective and stable to H2S gas at 25 °C, which shows promise for operating in medical diagnosis and environment monitoring. Excellent performance of the Fe2O3@CNT is due to the unique morphology of the nanocomposites made from uniformly dispersed Fe2O3 nanoparticles on the carbon surface without aggregation.

Real-time gas sensors that are ultra-sensitive, highly selective, and capable of fast response/recovery are highly in demand for environmental and health monitoring; however, advances in such gas sensors have been limited. Here we report a flexible and transparent sub-ppb gas detection film fabricated by in situ electrochemical oxidative polymerization on single-layer graphene (SLG). As polypyrrole molecules are uniformly formed with flat orientations on SLG, the resulting sensor film exhibits excellent sensitivity and selectivity with nearly perfect reversibility without heat treatment or light irradiation. The sensing mechanism is well explained by molecular interactions between the sensing material and the gas molecular species. The sensor exhibits a detection limit as low as 0.03 ppb NO2 and 0.04 ppb NH3 at room temperature and operates well, even at 70 °C, showing feasibility for wearable applications in high-precision gas sensing.

Dopamine (DA), a catecholamine hormone, is an important neurotransmitter that controls renal and cardiovascular organizations and regulates physiological activities. Abnormal concentrations of DA cause unfavorable neuronal illnesses such as Parkinson’s disease, schizophrenia, and attention deficit hyperactivity disorder (ADHD)/attention deficit disorder (ADD). However, the DA concentration is exceedingly low in patients and difficult to detect with existing biosensors. In this study, we developed an organic field-effect-transistor-type (OFET) non-enzyme biosensor using platinum nanoparticles decorated reduced graphene oxide (Pt_rGO) for ultrasensitive and selective DA detection. The Pt_rGOs were fabricated by reducing GO aqueous solution containing Pt precursors (PtCl4) with a chemical reducing agent. The Pt_rGOs were immobilized on graphene substrate by π–π interactions and a conducting-polymer source–drain electrode was patterned on the substrate to form the DA sensor. The resulting OFET sensor showed a...

Graphene oxide (GO) enwrapped SiO2/TiO2 hollow nanoparticles (GO-HNP) are synthesized by stobber method and used as a nanocarrier for loading protoporphyrin IX (PpIX). The synthesized nanoparticle has high dispersibitliy and high uniformity in diameter (ca. 50 nm). . Furthermore, this nanoparticle shows 808 nm laser induced PpIX release property (photo-induced "on-off" drug release system). The GO-HNP-PpIX is employed for inducing both photothermal therapy (PTT) and photodynamic therapy (PDT). The synergic effect of the PTT and PDT exhibits powerful anti-cancer property. When cancer cells are treated with GO-HNP-PpIX and irradiated with both visible light and 0.8 W cm-2 of 808 nm laser, the cell viability dropped dramatically to 2.5 %, which is approximately 13 times higher anticancer effect than previous stuty. Moreover, no significant cell damage has been observed in a condition of dark 808 nm laser irradiation. The GO-HNP-PpIX system suggests external stimuli responsive effieicnt anticancer treatment effect toward human breast cancer cells.

Research on the addition of suitable materials into perovskite solar cells (PSCs) for improved performance is as important as the fabrication of efficient perovskite films themselves. An attempt to enhance the performance of planar-type perovskite solar cells was performed by introducing graphene quantum dots (GQDs) onto a blocking TiO2 layer via O2 plasma treatment. Furthermore, the bandgap of the GQDs was tuned through their size control and the effects of the GQD size on cell performance were explored. The GQDs can induce fast electron extraction and the formation of the improved perovskite quality. The devices with appropriately sized-GQDs showed an average of 10% enhancement compared with those of cells without GQDs and achieved 19.11% as the best power conversion efficiency (PCE). Furthermore, GQDs contributed to the reduction in the extent of current–voltage hysteresis, which was attributed to the planar structure.

Recently, carbon nanomaterials are attractive for various applications owing to the benefits derived from their high electrical conductivity, chemical stability and large surface to volume ratio. However, the fabrication process of carbon nanomaterials is complicated and exhibits low productivity. Here we report the facile one-pot synthesis of highly porous 1D carbon nanotubes based on three-layered polymer nanofibers by using a dual-nozzle co-electrospinning technique to apply to an energy storage device. Specific capacitance (CG) of the porous carbon nanotube-based electrode is 401 F g−1, which is larger than that of the other carbon nanomaterials. Furthermore, the porous carbon nanotube exhibits excellent rate capability and cycle stability due to micro-/mesopores in the carbon structure enhancing the active surface area between carbon and the ions of the electrolytes. This unique fabrication technique is an effective approach for forming large scale highly porous carbon nanomaterials for diverse electrochemical applications.

Rendering a high crystalline perovskite film is integral to achieve superior performance of perovskite solar cells (PSCs). Here, we established a two-dimensional liquid cage annealing system, a unique methodology for remarkable enhancement in perovskite crystallinity. During thermal annealing for crystallization, wet-perovskite films were suffocated by perfluorodecalin with distinctively low polarity, nontoxic, and chemically inert characteristics. This annealing strategy facilitated enlargement of perovskite grain and diminution in the number of trap states. The simulation results, annealing time, and temperature experiments supported that the prolonged diffusion length of precursor ions attributed to the increase of perovskite grains. Consequently, without any complicated handling, the performance of perovskite photovoltaics was remarkably improved, and the monolithic grains which directly connected the lower and upper electrode attenuated hysteresis.

A bass frequency response enhanced flexible polyvinylidene fluoride (PVDF) based thin film acoustic actuator is successfully fabricated. High concentrations of various zinc oxide (ZnO) is embedded in PVDF matrix, enhancing the β phase content and the dielectric property of the composite thin film. ZnO acts as a nucleation agent for the crystallization of PVDF. A chemical vapor deposition grown graphene is used as electrodes, enabling high electron mobility for the distortion free acoustic signals. The frequency response of the fabricated acoustic actuator is studied as a function of the film thickness and filler content. The optimized film has a thickness of 80 μm with 30 wt% filler content and shows 72% and 42% frequency response enhancement in bass and midrange compared to the commercial PVDF, respectively. Also, the total harmonic distortion decreases to 82% and 74% in the bass and midrange regions, respectively. Furthermore, the composite film shows a promising potential for microphone applications. Most of all, it is demonstrated that acoustic actuator performance is strongly influenced by degree of PVDF crystalline.

The combination of reduced graphene oxide (RGO) with silica nanoparticles as shaping agents results in an enhanced surface area of RGO by the inhibition of π–π stacking between the RGO sheets, leading to enhanced electrochemical properties of the polyaniline/RGO/silica nanocomposite. The nanocomposite exhibits a multidimensional structure, in which urchin-like polyaniline nanofibers are grown on the RGO ball and the surface of the silica nanoparticle is entirely sealed with the polyaniline and RGO sheets. The nanocomposite also demonstrates efficient electrochemical properties due to the enhanced surface area, electrical conductivity, and synergetic effects between RGO and polyaniline. This method could pave the way to the development of advanced devices for energy-storage systems.

A new class of hierarchical α-Fe2O3/poly(3,4-ethylenedioxythiophene) (PEDOT) core/shell Janus-type hybrid nanoparticles (HNPs) was successfully synthesized using sonochemical, liquid–liquid diffusion-assisted crystallization, and vapor deposition polymerization methods. The synthesized α-Fe2O3/PEDOT HNPs exhibited several unique properties, including a large surface area, high conductivity, excellent electrochemical properties, and high chemical stability. In addition, the α-Fe2O3/PEDOT HNPs reduced the dynamic resistance of electrolyte ions, and enabled high charge–discharge rates and stable expansion of the cell voltage up to 2.0 V, thereby enabling high-performance supercapacitance. These results were attributed to synergetic effects between iron oxide (core structure with a negative working potential window) and PEDOT (shell structure with a positive working potential window), resulting in performance enhancements of specific capacitance (252.8 F g−1) and energy (136.3 W h kg−1) and power densities (10 526 W kg−1). The specific capacitance exhibited 92% retention after 1000 cycles. Additionally, a flexible supercapacitor based on the α-Fe2O3/PEDOT HNPs was successfully demonstrated using a hydrogel electrolyte. The fabricated all-solid-state symmetrical supercapacitor produced superior electrochemical and mechanical performance, even after several bending motions.

In the development of disease diagnoses, rapid responses to and accurate selectivity for target analytes are critical aspects. As one diagnostic approach, biosensors with high sensitivity and selectivity are investigated to detect disorder factors (e.g., endocrine disruptors and cancer oncoproteins). In this report, we demonstrate an aptamer-functionalized multidimensional hybrid conducting-polymer (3-carboxylated polypyrrole) plate (A_MHCPP) based field-effect transistor (FET) sensor to detect a platelet-derived growth factor (PDGF-BB). The multidimensional hybrid conducting-polymer plates (MHCPPs) are formed on the graphene surface by using electrodeposition and vapor deposition polymerization (VDP) steps. The amine-functionalized PDGF-B binding aptamers are then immobilized on the carboxylated polypyrrole surface by means of covalent bond formation (-CONH). The prepared FET sensors present high sensing ability toward PDGF-BB - as low as 1.78 fM among interfering biomolecules at room temperature.

A highly transparent paste adhesive is successfully fabricated by introducing graphene oxide (GO) to silicone paste adhesive by using a solvent-exchange method. The GO incorporated in the paste adhesive has a significant role in improving thermal conductivity, transparency and adhesive strength. The GO-embedded silicone paste is applied as a die-attach paste to light-emitting diodes (LEDs) in order to enhance the optical quality of the LEDs. The presence of GO in the die-attach layer of the LEDs gives rise to the enhancement of luminous intensity, effective heat dissipation, improvement of moisture barrier property as well as high adhesive strength. Consequently, the LEDs with the GO-embedded die-attach paste exhibit enhanced long-term stability. This novel approach provides a feasible and effective strategy for improving LED performance.

Hepatitis B virus (HBV) infection is a major worldwide health issue causing serious liver diseases, including liver cirrhosis and hepatocellular carcinoma. Monitoring the serum hepatitis B surface antigen (HBsAg) level is pivotal to the diagnosis of HBV infection. In this study, we describe multidimensional conductive nanofilm (MCNF)-based field-effect transistor (FET) aptasensor for HBsAg detection. The MCNF, composed of vertically oriented carboxylic polypyrrole nanowires (CPPyNW) and graphene layer, is formed using electropolymerization of pyrrole on the graphene surface and following acid treatment. The amine-functionalized HBsAg-binding aptamers are then immobilized on the CPPyNW surface through covalent bonding formation (i.e., amide group). The prepared aptasensor presents highly sensitive to HBsAg as low as 10 aM among interfering biomolecules with various deformations. Moreover, the MCNF-based aptasensor has great potential for practical application in the noninvasive real-time diagnosis because of its improved sensing ability to the human serum and artificial saliva.

Recently, using graphene oxide (GO) for “carbocatalysis” has been very attractive as a novel application of graphene-based nanomaterials and is expected to open a host of possibilities for chemical synthesis because of the abundance of natural carbon sources, as well as the low density, extensive chemical functionalization, hydrophilicity, low cost, and ease of preparation. Here, we demonstrate that the GO can play a role as a chemical oxidant for various CPs (polythiophene, polyaniline, and polypyrrole), and diverse graphene–CP composites (graphene–polythiophene, graphene–polyaniline, and graphene–polypyrrole) can simply and rapidly be synthesized by using the GO as both graphene precursor and chemical oxidant. The UV–vis analysis confirms that the GO has successfully polymerized the CPs and been transformed to reduced graphene oxide (RGO). The SEM and TEM analyses show that the CPs have successfully been coated on the few-layered graphene sheets. Raman analysis and series of FT-IR analyses have been con...

Hydrogen, a clean-burning fuel, is of key importance to various industrial applications, including fuel cells and the aerospace and automotive industries. However, hydrogen gas is odorless, colorless, and highly flammable; thus, appropriate safety protocol implementation and monitoring are essential. Highly sensitive hydrogen-gas leak detection and surveillance systems are needed; additionally, the ability to monitor large areas (e.g., cities) via wireless networks is becoming increasingly important. In this report, we introduce a radio frequency identification (RFID)-based wireless smart-sensor system, composed of a Pt-decorated reduced graphene oxide (Pt_rGO)-immobilized RFID sensor tag and an RFID-reader antenna-connected network analyzer to detect hydrogen gas. The Pt_rGOs, produced using a simple chemical reduction process, were immobilized on an antenna pattern in the sensor tag through spin coating. The resulting Pt_rGO-based RFID sensor tag exhibited a high sensitivity to hydrogen gas at unprecedentedly low concentrations (1 ppm), with wireless communication between the sensor tag and RFID-reader antenna. The wireless sensor tag demonstrated flexibility and a long lifetime due to the strong immobilization of Pt_rGOs on the substrate and battery-independent operation during hydrogen sensing, respectively.

In this work, we describe a simple method for the fabrication of a new class of graphene/free-standing nanofibrillar PEDOT/P(VDF-HFP) nanohybrid E-skin device. This E-skin exhibits enhanced contact surface area and piezo-resistivity with an extremely high gauge factor (320) under tensile strain, which combine to yield very high sensitivity to pressure (limit of detection = 0.5 Pa). Signals from even very weak motion, such as changes in facial expression and the pulse in the wrist, can be detected. Furthermore, this E-skin is sufficiently durable and reproducible. The E-skin device does not exhibit measurable changes in performance or observable signs of physical deterioration, even after over 1000 strain cycles, and is wearable and sufficiently biocompatible to be placed inside clothing or against human skin without causing irritation.

This work describes a ternary nanocomposite system, composed of poly(vinylidene fluoride) (PVDF), NH2-treated graphene nanodots (GNDs), and reduced graphene oxides (RGOs), for use in high energy density capacitor. When the RGO sheets were added to PVDF matrix, the β-phase content of PVDF became higher than that of the pristine PVDF. The surface-treatment of GNDs with an ethylenediamine can promote the hydrogen bonding interactions between the GNDs and PVDF, which promote the formation of β-phase PVDF. This finding could be extended to combine the advantages of both RGO and NH2-treated GND for developing an effective and reliable means of preparing PVDF/NH2-treated GND/RGO nanocomposite. Relatively small amounts of NH2-treated GND/RGO cofillers (10 vol %) could make a great impact on the α → β phase transformation, dielectric, and ferroelectric properties of the ternary nanocomposite. The resulting PVDF/NH2-treated GND/RGO nanocomposite exhibited higher dielectric constant (ε' ≈ 60.6) and larger energy density (U(e) ≈ 14.1 J cm(-3)) compared with the pristine PVDF (ε' ≈ 11.6 and U(e) ≈ 1.8 J cm(-3)).

We report a rapid-response and high-sensitivity field-effect transistor (FET)-based sensor with specificity towards glucose, based on reduced graphene oxide (rGO)-carboxylated polypyrrole (C-PPy) nanotube (NT) hybrids as the conductive channel. The rGO, C-PPy NTs, and rGO/C-PPy NT hybrids were characterized using Raman spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The results indicate that a well-organized structure was successfully prepared, based on specific interactions between the C-PPy NTs and the graphene sheets. Reliable electrical contacts were developed between the rGO/C-PPy NTs and the patterned-microelectrodes, which remained stable when exposed to the liquid-phase electrolyte. Liquid-ion-gated FETs composed of these rGO/C-PPy NT hybrids exhibited hole-transport behavior with higher conductivity than those of graphene sheets or C-PPy NTs because the C-PPy NTs formed a bridge between the graphene layers, resulting in effective electron transport. Glucose oxidase (GOx) was used as the capture probe, and was tightly combined with C-PPy NTs via a chemical coupling reaction, and glucose detection was performed via GOx, which catalyzes the oxidation of glucose in the rGO/C-PPy NTs hybrid FET biosensor. The FET biosensor provided a rapid response (

Graphene quantum dots (GQDs) with two different diameters were modified with a EuIII–macromolecule complex and applied in dual emission fluorescent sensors for detection of Bacillus anthracis spores. The Eu-GQD sensors exhibited a morphology of ultrafine particles, increased surface-to-volume ratio, enhanced dispersibility, and extraordinary sensitivity. The 3 nm Eu-GQDs showed three emission bands, which are ascribed to the emission from the blue GQDs (435 nm) and the red [(Eu)–(DPA)] complex (593 nm and 616 nm). Accordingly, incorporation of the GQDs as a non-interfering internal calibration makes it possible for use as a ratiometric sensor. The time dependent fluorescence response study revealed that the reaction was complete within 8 s, thus enabling rapid detection of B. anthracis spores. It is noteworthy that the Eu-GQD sensors exhibited an extraordinary limit of detection (LOD) of ca. 10 pM towards B. anthracis, which is six orders of magnitude smaller than the infectious dose of the spores (60 μM). Furthermore, the selectivity study indicates that Eu-GQD sensors have an outstanding selectivity of 103-fold for DPA over competing aromatic ligands.

Electrophotorheological (EPR) fluids, whose rheological activity is dually responsive to light and electric fields (E fields), is formulated by mixing photosensitive spiropyran-decorated silica (SP-sSiO2) nanoparticles with zwitterionic lecithin and mineral oil. A reversible photorheological (PR) activity of the EPR fluid is developed via the binding and releasing mechanism of lecithin and merocyanine (MC, a photoisomerized form of SP) under ultraviolet (UV) and visible (VIS) light applications. Moreover, the EPR fluid exhibits an 8-fold higher electrorheological (ER) performance compared to the SP-sSiO2 nanoparticle-based ER fluid (without lecithin) under an E field, which is attributed to the enhanced dielectric properties facilitated by the binding of the lecithin and SP molecules. Upon dual application of UV light and an E field, the EPR fluid exhibits high EPR performance (ca. 115.3 Pa) that far exceeds its separate PR (ca. 0.8 Pa) and ER (ca. 57.5 Pa) activities, because of the synergistic contribut...

In this study, a three-dimensional (3D) mesoporous plasma-reduced graphene oxide web (mPrGO web) was fabricated via lyophilization of graphene oxide (GO) solution and subsequent plasma reduction. The lyophilized graphene oxide web (GO web) was successfully reduced by a short plasma treatment (2 s) using a commercially available plasma apparatus. The degree of reduction of the mPrGO web was determined by the applied plasma power (W) of the apparatus; the optimum power level for effective reduction was identified. The as-synthesized mPrGO web showed a high degree of reduction and robust graphitic characteristics, with a unique crack-like mesoporous structure created on corrugated graphene sheets. In addition to the above characteristics, the mPrGO web possessed a 3D web-like architecture that provided enhanced surface area along with ion-transportable channels derived from lyophilization. Owing to the synergistic effect of lyophilization and plasma reduction, the mPrGO web exhibited high electrical conductivity (87 S cm

An optimized configuration for nanomaterials in working electrodes is vital to the high performance of dye-sensitized solar cells (DSSCs). Here, a fabrication method is introduced for multi-shell TiO2 hollow nanoparticles (MS-TiO2-HNPs) via a sol–gel reaction, calcination, and an etching process. The prepared uniform MS-HNPs have a high surface area (ca. 171 m2 g−1), multireflection, and facile electrolyte circulation and diffusion. During the MS-HNP fabrication process, the amount of SiO2 precursor and H2O under reaction has a significant effect on aggregation and side reactions. The etching process to obtain pure TiO2 is influenced by anatase crystallinity. Additionally, single-shell (SS)-TiO2-HNPs and double-shell (DS)-TiO2-HNPs are synthesized as a control. The MS-TiO2-HNPs exhibit a high surface area and enhance light reflectance, compared with the SS- and DS-TiO2-HNPs of the same size. The power conversion efficiency of the optimized MS-TiO2-HNP-based DSSCs is 9.4%, compared with the 8.0% efficiency demonstrated by SS-TiO2-HNP-DSSCs (a 17.5% improvement). These results enable the utilization of multifunctional MS-HNPs in energy material applications, such as lithium ion batteries, photocatalysts, water-splitting, and supercapacitors.

High-optical-quality white light-emitting diodes (LEDs) are leading candidates for next-generation lighting and numerous other potential applications. In this work, a simple and innovative strategy based on semi-solidification was used to prepare white LEDs with a highly uniform illumination distribution. Semi-solidification facilitates uniform dispersion of fluorescent phosphors throughout the LED encapsulant by adopting a B-stage intermediate step, thereby enabling superior color uniformity in the LED. This approach is based on the control of the curing process and offers a reasonable and effective solution for problems associated with conventional LEDs, including the yellow ring phenomenon that arises from non-uniform illumination. Our novel and simple approach provides a facile route for the fabrication of novel, high-performance LED encapsulants. This method is effective for the enhancement of luminous efficacy, long-term stability, and color uniformity of LEDs, indicating their potential use in industrial and practical applications.

Highly dispersible graphene oxide (GO) sheets of uniform submicrometer size were successfully fabricated from pristine graphite using a simple mechanochemical process. The GO flake morphology was transformed into a spherical form, and the density was decreased slightly via the ball-milling process. Ball-milled GO can be used as an electrorheological (ER) material because of its small particle size, low conductivity, and outstanding dispersibility in silicone oil. We found that the 2-h ball-milled GO-based ER fluid had the best ER performance (shear stress of 78.5 Pa and 630% ER efficiency), which was double that of the nonmilled GO-based ER fluid. The response time to form a fibrillar structure along the applied electric field direction and the recovery time to the starting level decreased with increasing ball-milling time. Additionally, the retarded settling velocity of isolated GO sheets and the electrostatic repulsion between oxygen functional groups on the GO sheets combined to improve the antisedimentation property. The ability to control the size of graphene sheets is a great opportunity to advance graphene commercialization in a high-quality, scalable production setting.

A new class of graphene–polyselenophene (PSe) hybrid nanocomposite was successfully synthesized using an in situ synthetic method. The synthesized graphene–PSe nanocomposite exhibited unique properties including a large voltage window, high conductivity, and good mechanical properties. The graphene–PSe nanohybrid reduced the dynamic resistance of electrolyte ions and enabled high charge–discharge rates, thereby enabling high-performance supercapacitance. The results were attributed to synergetic effects between graphene and conducting polymers (CPs), which enhanced charge transport, surface area, and hybrid supercapacitance by combining the properties of electrolytic double-layer capacitors (EDLCs) with those of psedocapacitors. Additionally, a flexible supercapacitor based on the graphene–PSe nanohybrid was successfully demonstrated. To fabricate binder-free supercapacitors, chemical vapor deposition (CVD) and vapor deposition polymerization (VDP) methods were employed. The fabricated all-solid-state sup...

Highly conductive, transparent, flexible and scalable graphene hybrid thin films with controlled domain size were successfully fabricated via a mechanochemical method, screen printing and pressure-assisted reduction process.

With developments in technology, tremendous effort has been devoted to produce flexible, scalable, and high-performance supercapacitor electrode materials. This report presents a novel fabrication method of highly flexible and scalable electrode material for high-performance supercapacitors using solution-processed polyaniline (PANI)/reduced graphene oxide (RGO) hybrid film. SEM, TEM, Raman, and XPS analyses show that the PANI/RGO film is successfully synthesized. The percentages of the PANI component in the film are controlled (88, 76, and 60%), and the maximum electrical conductivity (906 S cm−1) is observed at the PANI percentage of 76%. Notably, electrical conductivity of the PANI/RGO film (906 S cm−1) is larger than both PANI (580 S cm−1) and RGO (46.5 S cm−1) components. XRD analysis demonstrates that the strong π–π interaction between the RGO and the PANI cause more compact packing of the PANI chains by inducing more fully expanded conformation of the PANI chains in the solution, leading to increase in the electrical conductivity and crystallinity of the film. The PANI/RGO film also displays diverse advantages as a scalable and flexible electrode material (e.g., controllable size and great flexibility). During the electrochemical tests, the film exhibits high capacitance of 431 F g−1 with enhanced cycling stability.

Mercury (Hg) is highly toxic but has been widely used for numerous domestic applications, including thermometers and batteries, for decades, which has led to fatal outcomes due to its accumulation in the human body. Although many types of mercury sensors have been developed to protect the users from Hg, few methodologies exist to analyze Hg(2+) ions in low concentrations in real world samples. Herein, we describe the fabrication and characterization of liquid-ion gated field-effect transistor (FET)-type flexible graphene aptasensor with high sensitivity and selectivity for Hg. The field-induced responses from the graphene aptasensor had excellent sensing performance, and Hg(2+) ions with very low concentration of 10 pM could be detected, which is 2-3 orders of magnitude more sensitive than previously reported mercury sensors using electrochemical systems. Moreover, the aptasensor showed a highly specific response to Hg(2+) ions in mixed solutions. The flexible graphene aptasensor showed a very rapid response, providing a signal in less than 1 s when the Hg(2+) ion concentration was altered. Specificity to Hg(2+) ions was demonstrated in real world samples (in this case samples derived from mussels). The aptasensor was fabricated by transferring chemical vapor deposition (CVD)-grown graphene onto a transparent flexible substrate, and the structure displayed excellent mechanical durability and flexiblility. This graphene-based aptasensor has potential for detecting Hg exposure in human and in the environment.

Thin pDMAEMA shells were formed on the surface of silica nanoparticles via vapor deposition polymerization. Scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and elemental analysis have been used to characterize the resulting pDMAEMA-coated silica nanoparticles. Electron microscopy studies reveal that the thin polymer shell is formed on the silica surface. In this work, the particle diameter can be controlled (from ~19 to ~69 nm) by varying the size of silica core. The antibacterial performance of the core-shell nanoparticles was investigated against both Gram-positive (Escherichia coli) and Gram-negative (Staphylococcus aureus) bacteria. Importantly, the nano-sized pDMAEMA particles presented antibacterial activity against both bacteria without additional quaternization due to its enlarged surface area. Additionally, the bactericidal efficiency was enhanced by reducing the particle size, because the expanded surface area of the cationic polymer nanoparticles provides more active sites that can kill the bacteria.

Large-scale FET-type graphene micropattern (GM) nano-biohybrid-based immunosensor (GMNS) is fabricated in a controlled fashion to detect human immunodeficiency virus 2 antibody. Flexible GMNS shows a highly sensitive response and excellent mechanical bendability. The flexible GMNS in fluidic systems also has a stable response. This is the first experimental demonstration of a large-scale flexible fluidic FET-type immunoassay based on GM nano-biohybrids.

The polyaniline/poly(styrene sulfonate) (PANI/PSS)-coated silica spheres with three different sizes (50, 100, and 250 nm) are fabricated through seed-coating method and adopted as dispersing materials for electrorheological (ER) fluids to examine the influence of particle diameter on ER activity. Interestingly, the ER properties of PANI/PSS-coated silica spheres exhibit a dependence on their size. Performances of PANI/PSS-coated silica spheres-based ER fluids enhanced with decreasing the diameter of particle. It is believed that the size effect played a dominant role in enhancing the performance of ER fluid. Furthermore, the fibrillation phenomenon of prepared PANI/PSS-coated silica spheres-based ER fluid was observed via an optical microscope in the applied electric field. Sedimentation properties were also analyzed to provide additional insight into the size effect of ER fluids.

We investigated high-yield hydrogen peroxide generation using a membrane electrode assembly (MEA) with a carbon fiber (CF)-coated mesh substrate in a solid polymer electrolyte electrolyzer. Current efficiency (52%) and power consumption (0.3 Wh g−1) for this MEA were 1.5 times higher and 2 times lower at −0.1 V vs. Ag/AgCl than those of reported values. These significant improvements were presumed to be attributed to enhanced oxygen mass transfer and reduced charge transfer resistance arising from the CF-coated mesh substrate in the MEA. Keywords: SPE electrolyzer, Hydrogen peroxide, Carbon fiber, Mesh substrate, Membrane electrode assembly

Titanium dioxide (TiO2) nanorod-decorated graphene sheets have been synthesized by a simple non-hydrolytic sol–gel approach and demonstrated to be a highly effective dispersing material for electrorheological fluids. Electron microscopy and X-ray diffraction analysis indicated that the TiO2 nanorods with a high crystallinity are well-dispersed and successfully anchored on the graphene sheet surface through the formation of covalent bonds between Ti and C atoms. Furthermore, electro-responsive properties of graphene sheets decorated with TiO2 nanorods are investigated on the basis of the dielectric loss model. The dielectric property analysis based on the dielectric loss model clarifies that an introduction of TiO2 nanorods has been coupled with the larger achievable polarizability and short relaxation time of interfacial polarization. Consequently, the TiO2 nanorod-decorated graphene sheets exhibit consistently higher ER efficiency than that of GO sheets and show unprecedented electro-responsive performance in extremely low concentration ER materials (

Carbon nanotubes with an average diameter of 50 nm were produced from polypyrrole nanotubes fabricated with a surfactant mediated microemulsion polymerization. A simple production of polypyrrole nanotube precursor was possible through a proper selection of surfactant and initiator in microemulsion system. A subsequent thermal treatment of conducting polymer precursor generated novel carbon nanotubes. Electron microscopy images confirmed the successful formations of polypyrrole and carbon nanotubes. A series of carbon nanotube pastes were formulated with combination of binders and fillers. The field emission characteristic of these carbon nanotubes was monitored by I–V curves. Constant current tests revealed the lifetime of carbon nanotube field emitters derived from polypyrrole nanotubes.

The effect of graphene on the crystallization behavior of graphene/poly(vinyl alcohol) (PVA) nanocomposites is investigated in terms of the heterogeneous nucleation effect using Fourier transform infrared spectroscopy and differential scanning calorimetry. Nanometer-sized graphenes with disc-type shape are successfully fabricated by transversal cutting of platelet carbon nanofibers, and the graphene/PVA nanocomposites are prepared by varying the concentration of graphene using a solution-casting method. The graphene/PVA nanocomposites exhibit an enhanced degree of crystallization, increasing to 18.8% at a graphene concentration of 0.5 wt%. The graphene acts as an effective nucleating agent during the crystallization process, enhancing the degree and rate of crystallization. In addition, the graphene/PVA nanocomposites with a high graphene content have markedly improved mechanical properties. Mechanical properties, including hardness and elastic modulus, of the prepared graphene/PVA nanocomposites are analyzed using an atomic force microscopy nanoindentation method. The graphene plays a key role in increasing the crystallinity by acting as an effective nucleating agent at low concentrations ( 1.0 wt%).

Rapid and precise discrimination of various odorants is vital to fabricating enhanced sensing devices in the fields of disease diagnostics, food safety, and environmental monitoring. Here, we demonstrate an ultrasensitive and flexible field-effect transistor (FET) olfactory system, namely, a bioelectronic nose (B-nose), based on plasma-treated bilayer graphene conjugated with an olfactory receptor. The stable p- and n-type behaviors from modified bilayer graphene (MBLG) took place after controlled oxygen and ammonia plasma treatments. It was integrated with human olfactory receptors 2AG1 (hOR2AG1: OR), leading to the formation of the liquid-ion gated FET-type platform. ORs bind to the particular odorant amyl butyrate (AB), and their interactions are specific and selective. The B-noses behave as flexible and transparent sensing devices and can recognize a target odorant with single-carbon-atom resolution. The B-noses are ultrasensitive and highly selective toward AB. The minimum detection limit (MDL) is as low as 0.04 fM (10(-15); signal-to-noise: 4.2), and the equilibrium constants of OR-oxygen plasma-treated graphene (OR-OG) and ammonia plasma-treated graphene (-NG) are ca. 3.44 × 10(14) and 1.47 × 10(14) M(-1), respectively. Additionally, the B-noses have long-term stability and excellent mechanical bending durability in flexible systems.

PURPOSE: A graphene sheet using inkjet printing and a wideband dipole antenna application are provided to minimize the loss of raw material and time. CONSTITUTION: Waterborne graphene oxide nano particle solution is manufactured and is used for conductive ink of inkjet printing. The chemical characteristic of the waterborne graphene oxide nano particle solution is changed in order to form a detailed pattern on a supporting material. The waterborne graphene oxide nano particle solution is injected to a printer head, and an oxide graphene thin film is formed. The supporting material including the oxide graphene thin film is located in a vapor deposition reactor, and an oxidation-reduction reaction is executed. A graphene sheet based broadband dipole antenna electrode is connected to an antenna analysis device, and the performance of the antenna is measured.

The crystallization behavior of poly(vinyl alcohol) (PVA) in the presence and absence of polypyrrole nanoparticles (PPy NPs) was investigated in terms of the heterogeneous nucleation effect of PPy NPs using FTIR, X-ray diffraction, differential scanning calorimeter and polarized optical microscope analysis. PPy NPs were prepared by dispersion polymerization method stabilized by PVA in aqueous solution. A polymer nanocomposite with uniform dispersity could be readily obtained due to the enhanced compatibility between the filler and matrix. Compared with the PPy NP-absent PVA, the PPy NP/PVA nanocomposite exhibited an enhanced degree of crystallinity. The degree of crystallinity increased up to 17% at the PPy NP concentration of 1 wt%, compared to the pristine PVA. The PPy NP acted as an effective nucleating agent during the crystallization process, thereby enhancing the degree and rate of crystallization. The kinetics study of the crystallization also revealed the decreased value of the Avrami coefficient in the case of the PPy NP/PVA nanocomposite.

We demonstrate a general method for tuning the color performance of white organic light-emitting diodes (WOLEDs) by inserting 0.5 nm thick red emitting layer in different location of blue phosphorescent emitting layer. The Commission Internationale de L'Eclairage (CIE) coordinates of WOLEDs were dependent on the position of red emitting layer and they were correlated with recombination zone of the blue phosphorescent emitting layer. Red shift of white CIE was observed as the location of red emitting layer get close to recombination zone of blue emitting layer. In addition, CIE of WOLEDs was kept stable between 100 cd/m2 and 10,000 cd/m2.

The pore structures of commercial pitch and PAN-based activated carbon fibers (ACFs) were investigated. The pore size and pore size distribution of pitch-based ACFs were measured by nitrogen adsorption isotherms and 129Xe NMR spectroscopy and compared with each other. Scanning tunneling microscopy showed that the ACFs were composed of spherical microdomain units the size of a few nanometers. The activation mechanism of ACFs was considered and explained by novel hypothesis; the concept of microdomain structure of ACFs was considered and explained to overcome limitation of the conventional fractal hypothesis. Whereas micropores were generated on each microdomain, the origin of mesopores was interdomain pores, resulting from the microdomain hypothesis.

Interlayer-free phosphorescent white organic light-emitting diodes (PHWOLEDs) with a mixed-host emitting structure in red emitting layer were developed and device performances were investigated according to the host composition in the red emitting layer. Device performances could be effectively managed by a simple change of host materials in the red emitting layer. A high quantum efficiency was obtained in PHWOLEDs with electron transport-type host in the red emitting layer and red emission was strong in PHWOLEDs with mixed-host in the red emitting layer. In addition, stable color performances were obtained in electron transport-type host rich devices.

A deep blue phosphorescent organic light-emitting diode was developed using a diphenyldi(4-(9-carbazoly)lphenyl)silane(SiCa) host material and a tris((3,5-difluoro-4-cyanophenyl)pyridine) iridium(FCNIr) dopant material. Triplet bandgap of the SiCa was 3.0 eV, while triplet bandgap of the FCNIr was 2.8 eV. Light-emitting performances of blue devices were investigated by changing doping concentration of the FCNIr and a pure blue emission with a color coordinate of (0.15, 0.19) could be obtained.