Synthesis and Characterisations of TiO₂Coated Multiwalled Carbon Nanotubes/Graphene/Polyaniline Nanocomposite for Supercapacitor Applications

Nowadays with ever increasing demand of energy, developing of alternative power sources is an important issue all over the world. In this respect we have prepared nanocomposites based on metal oxide (titanium oxide) coated multiwalled carbon nanotubes (MWCNTs)/polyaniline (PANI) with graphene and without graphene and studied their electrochemical performance. The formation of the polymer in the nanocomposites was confirmed by the Fourier Transform Infrared Spectroscopy (FTIR) study. The morphological characterisations were carried out by the Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM). To characterize the prepared nanocomposites electrode, a cyclic voltammetry test for measuring specific capacitance, and an impedance test were conducted. The highest value of specific capacitance obtained for the TiO2 coated MWCNTs/PANI nanocomposite was 443.57 F/g at 2 mV/s scan rate. Upon addition of graphene nanosheet to the TiO2 coated MWCNTs in a weight ratio of (9:1) the specific capacitance value increased to 666.3 F/g at the same scan rate, also resulting in an increase in energy density and power density.

Synthesis and electrochemical properties of three-dimensional graphene/polyaniline composites for supercapacitor electrode materials

To improve the specific capacitance and rate capability of electrode material for supercapacitors, a three-dimensional graphene/polyaniline （3DGN/PANI） composite is prepared via in situ polymerization on GN hydrogel. PANI grows on the GN surface as a thin film, and its content in the composite is controlled by the concentration of the reaction monomer. The specific capacitance of the 3DGN/PANI composite containing 10 wt% PANI reaches 322.8 F.g-1 at a current density of 1 A.g-1, nearly twice as large as that of the pure 3DGN （162.8 F.g-1）. The capacitance of the composite is 307.9 F.g-1 at 30 A.g-1 （maintaining 95.4%）, and 89% retention after 500 cycles. This study demonstrates the exciting potential of 3DGN/PANI with high capacitance, excellent rate capability and long cycling life for supercapacitors.

A flexible solid-state supercapacitor based on graphene/polyaniline paper electrodes

The direct coating of graphene sheets obtained by electrochemical exfoliation on commercial paper renders the preparation of highly conductive flexible paper substrate for subsequent deposition of polyaniline (PANi) nanorods via electrochemical polymerization. The deposit ion of PANi can be well-controlled by adjusting the electrochemical polymerization time, leading to the formation of PANi coated graphene paper (PANi-GP). The as-prepared electrode exhibited high areal capacitance of 176 mF cm^-2 in three-electrode system at a current density of 0.2 mA cm^-2 which is around 10 times larger than that of pris-tine graphene paper due to the pseudocapacitive behavior of PANi. In-situ Raman test was used to determine the molecular changes during redox process of PANi. More importantly, all-solid-state symmetric capacitor assembled with two PANi-GP electrodes in a polymer electrolyte delivered an areal capacitanee of 123 mF cm^-2, corresponding to an areal energy density of 17.1 μWh cm^-2 and an areal power density of 0.25 mW cm^-2. The symmetric capacitor held a capacitive retention of 74.8% after 500 bending tests from 0 to 120°, suggesting the good flexibility and mechanical stability. These results showed the great promising application in flexible energy-storage devices.

Synthesis and microwave absorption properties of graphene-oxide(GO)/polyaniline nanocomposite with Fe_3O_4 particles

In order to investigate the impedance matching properties of microwave absorbers,the ternary nanocomposites of GO/PANI/Fe3O4（GPF） are prepared via a two-step method,GO/PANI composites are synthesized by dilute polymerization in the presence of aniline monomer and GO,and GO/PANI/Fe3O4 is prepared via a co-precipitation method.The obtained nanocomposites are characterized by scanning electron microscopy（SEM）,X-ray diffraction（XRD）,and Fourier transform infrared spectroscopy（FTIR）,respectively.The microwave absorbability reveals enhanced microwave absorption properties compared with GO,PANI,and GO/PANI.The maximum reflection loss of GO/PANI/Fe3O4 is up to-27 dB at 14 GHz with its thickness being 2 mm,and its absorption bandwidths exceeding-10 dB are more than 11.2 GHz with its thickness values being in the range from 1.5 mm-4 mm.It provides that GO/PANI/Fe3O4 can be used as an attractive candidate for microwave absorbers.

Synthesis and microwave absorption properties of graphene-oxide(GO)/polyaniline nanocomposite with gold nanoparticles

A composite of graphene/PANI/GAunano is synthesized using the co-blend method. The morphologies and microstructures of samples are examined by transition electron microscopy(TEM) and Fourier transform infrared spectroscopy(FTIR). Moreover, the microwave absorption properties of both graphene/PANI and GO/PANI/ GAunano composites are investigated in a microwave frequency band from 1 GHz to 18 GHz. The maximum reflection loss(RL) of GO/PANI/GAunano with a thickness of 2 mm is up to-24.61 d B at 15.45 GHz, and the bandwidth corresponding to RL at-10 d B can reach 4.08 GHz(from 13.92 GHz to 18.00 GHz) for a 2-mm-thick layer. The electromagnetic data demonstrate that GO/PANI/GAunano can be used as an attractive candidate for microwave absorbers.

Investigation of the Electro-Mechanical Behavior of Hybrid Polyaniline/Graphene Nanocomposites Fabricated by Dynamic Interfacial Inverse Emulsion Polymerization

This paper describes a study on electrical resistivity under loading of polyaniline (PANI)/graphene nanocomposite powders and compacts. The composites were prepared by an in-situ interfacial dynamic inverse emulsion polymerization technique under sonication of aniline in the presence of graphene sheets in chloroform. During polymerization the graphene nanoplatelets are coated with PANI and are well dispersed both in the polymeric suspension and then in the dried polymer matrix as evidenced by cryogenic transmission electron microscopy (Cryo-TEM) and high resolution scanning microscopy (HRSEM). The presence of graphene nanoplatelets lowers the electrical resistivity of the polyaniline by two orders of magnitude for both the powder and the compact composites as demonstrated by their electrical resistance measurements conducted under loading. The lowest measured electrical resistivity values were 5 Ω·cm for 33% wt. graphene powder and 8 Ω·cm for 41% wt. graphene compacted composites. Cyclic electrical measurements under loading showed a distinct reproducible dependence of the bulk resistivity vs. applied pressure. This repetition is a key component for electro-mechanical sensors. To the authors’ best knowledge, this is the first report on polymerization of aniline in presence of graphene by the in-situ interfacial dynamic inverse emulsion polymerization technique and also the first report on cyclic electrical measurements under pressure of PANI/graphene nanocomposites.

Three-dimensional Porous Graphene/Polyaniline Hybrids for High Performance Supercapacitor Electrodes

Graphene-based composites took extensive attraction as electrodes for supercacitors these years.Three-dimensional cross-linking porous graphene(3D rGO-m)was obtained by KOH activation to graphene modified by 1,2,4-triaminobenzene.3D porous graphene/polyaniline hybrids(3D rGO-m/PANI)was prepared by the in-situ chemical oxidative polymerization.The rGO-m are reconstructed from 2D to 3D porous structure after KOH activation.The PANI nanorod arrays are successfully decorated on the surface of the 3D porous graphene sheets.The specific capacitance of the 3D rGO-m/PANI hybrids reach 985 F/g at 0.5 A/g.The capacitance retention of 3D rGO-m/PANI maintains 90%of its initial capacity after 1000 cycles,while rGO-m/PANI only keeps 83%of its initial capacity,the cycling stability of both hybrids are higher than that of pure PANI(69%).

First principles insights into oxide/polymer composites: SrTiO_(3) /polyaniline/graphene

A detailed computational investigation,based on density functional theory,of the interaction of polyani-line(PANI)and graphene nanoribbons(GNRs)with SrTiO_(3) is presented.The adsorption of PANI in var-ious oxidation states and co-adsorption with GNRs is found to be thermodynamically favourable.Ad-sorbed PANI introduces N and C 2p states into the SrTiO_(3) bandgap,while co-adsorption of PANI and GNRs leads to a bridging of the gap and semi-metallic behaviour,thus rendering the electrical properties highly sensitive to the loading of the GNRs/PANI in the composites.Modelling the lattice dynamics of the composites predicts a 68-88%reduction in the lattice thermal conductivity due to reduced phonon group velocities.Taken together,these findings provide insight into the growing number of experimental studies highlighting the enhanced thermoelectric performance of oxide-polymer composites and indicate co-adsorption with graphene as a facile direction for future research.

High-performance supercapacitor based on ultralight and elastic three-dimensional carbon foam/reduced graphene/polyaniline nanocomposites

A novel supercapacitor based on ultralight and elastic three-dimensional (3D) porous melamine foam (MF)-derived macroporous carbon (3DPMFDMC)/reduced graphene oxide (rGO)/polyaniline (PANI) nanocomposites (denoted as 3DPMFDMC/rGO/PANI) were fabricated. By high temperature carboniza-tion, the commercial MF soaked in GO solution was prepared into ultralight and elastic 3DPMFDMC, the rGO were uniformly distributed into 3DPMFDMC to obtain 3DPMFDMC/rGO, and finally PANI was grown on the 3DPMFDMC/rGO by using in situ chemical oxidation polymerization method. The obtained 3DPMFDMC/rGO/PANI nanocomposites were characterized by SEM, FT-IR and Raman. The results showed the uniform distribution of rGO connected the broken fibers of 3DPMFDMC produced in the high temperature carbonization to improve the electrical conductivity and also enlarged the specific surface area of nanocomposites greatly. Lots of PANI were vertically arrayed on the surface of 3DPMFDMC/rGO. 3DPMFDMC/rGO/PANI exhibited a rapid electron/mass transport. Owing to its special structures and nanocomposites, the supercapacitor showed good electrical performance with a specific capacitance of 1870 F/g at the current density of 1 A/g. Moreover, the specific capacitance remained 95.4%after 1000 charging/discharging cycles at a current density of 5 A/g.

A highly sensitive dopamine sensor based on a polyaniline/reduced graphene oxide/Nafion nanocomposite

A nanocomposite of polyaniline/reduced graphene oxide（PANI-r GO） was synthesized using a hydrothermal method. The product was characterized by FT-IR, Raman spectra, XRD, SEM and TEM.Then the hybrid material of PANI-r GO and Nafion（PANI-rGO-NF） was prepared and used to modify glassy carbon electrode for the trace determination of dopamine（DA） employing differential pulse voltammetry（DPV）. It was found that the hybrid material showed good catalytic activity toward the oxidation of DA, and no response to ascorbic acid（AA） and uric acid（UA） was observed, suggesting a high selectivity of the sensor toward DA. The peak currents were linearly correlated with the concentration of DA in the range from 0.05 mmol/L to 60.0 mmol/L（R = 0.996） and 60.0 mmol/L to 180.0 mmol/L（R = 0.996） with a detection limit of 0.024 mmol/L（S/N = 3）. The modified electrode also exhibited excellent repeatability and stability.

One-Step Synthesis of Graphene/Polyaniline Nanotube Composite for Supercapacitor Electrode

Graphene/polyaniline nanotube （GPNT） composite was synthesized using Vitamin C as both the template of polyaniline nanotube via in situ polymerization of aniline and the reducing agent of graphene oxide. The pure polyaniline （PANI）, graphene/PANI composite （GP） （using hydrazine monohydrate instead of VC） and GO/PANI composite were also prepared. IR spectroscopy and morphologies of the as-prepared samples were characterized. And the electrochemical performances were conducted on a three-electrode cell. IR spectroscopy demonstrated the in- teraction between graphene and PANI nanotube in GPNT, which is beneficial to enhance the electrochemical performance of the composite electrode. Surface morphology showed PANI nanotube with outer diameter of 140 nm in GPNT. GPNT composites exhibited better electrochemical performances than GP composite and pure PANI. The electrochemical performances showed that the specific capacitance of GPNT was 561 F/g which is more than that of either GP or PANI, it is not only due to the graphene which can provide good electrical conductivity and high specific surface area, but also associated with a good redox activity of ordered PANI nanotubes. The as-prepared GPNT composites with higher conductivity, lower resistance and better cycle life in our laboratory are promising electrode materials for high-performance electrical energy storage devices.

Sensitive electrochemical DNA sensor for the detection of HIV based on a polyaniline/graphene nanocomposite

A nanocomposite of polyaniline/graphene(PAN/GN)was prepared using reverse-phase polymerization.The nanocomposite material was dropcast onto a glassy carbon electrode(GCE).Then,a single-stranded DNA(ssDNA)probe for HIV-1 gene detection was immobilized on the modified electrode,and the negative charged phosphate backbone of the HIV-1 was bound to the modified electrode surface via p-p*stacking interactions.The hybridization between the ssDNA probe and the target HIV-1 formed doublestranded DNA(dsDNA),and the electron transfer resistance of the electrode was measured using impedimetric studies with a[Fe(CN)6]^(3-/4-)redox couple.Under the optimized experimental conditions,the change of the impedance value was linearly related to the logarithm of the concentration of HIV genes in the range from 5.0×10^(-16)M to 1.0×10^(-10)M(R=0.9930),and the HIV sensor exhibited a lower detection limit of 1.0×10^(-16)M(S/N=3).The results show that this biosensor presented wonderful selectivity,sensitivity and specificity for HIV-1 gene detection.Thus,this biosensor provides a new method for the detection of HIV gene fragments.

An Acetylcholinesterase Biosensor Based on Graphene/ Polyaniline Composite Film for Detection of Pesticides

This work reports a sensitive amperometric biosensor for organophosphate pesticides （OPs） fabricated through modifying glassy carbon electrode with acetylcholinesterase （ACHE） immobilized on graphene/polyaniline （G/PANI） composite film. The obtained G/PANI composite films show large specific area, high conductivity, good biocompatibility, and fast redox properties and have perfect layered and encapsulated structures. The as-prepared biosensor shows high affinity to acetylthiocholine （ATC1） with a Micbaelis-Menten constant value of 0.20 mmol/L. Furthermore, based on the inhibition of the enzymatic activity （immobilized ACHE） caused by the model compound of carbaryl （one kind of pesticides）, it is found that the inhibition activity of carbaryl is proportional to its concen- tration ranging from 38 to 194 ngomL-1. The developed biosensor shows a detection limit of 20 ngomL-1 （S/N~ 3） for OPs detection and exhibits good performance such as good reproducibility and acceptable stability, which makes it possible to provide a new and promising tool for the analysis of enzyme inhibitors.

Polyaniline-coated selenium/carbon composites encapsulated in graphene as efficient cathodes for Li-Se batteries

In this work, we developed a polyaniline （PANI）-coated selenium/carbon nanocomposite encapsulated in graphene sheets （PANI@Se/C-G）, with excellent performance in Li-Se batteries. The PANI@Se/C-G nanostructure presents attractive properties as cathode of Li-Se batteries, with a high specific capacity of 588.7 mAh·g^-1 at a 0.2C （1C = 675 mA·g^-1） rate after 200 cycles. Even at a high rate of 2C, a high capacity of 528.6 mAh·g^-1 is obtained after 500 cycles. The excellent cycle stability and rate performance of the PANI@Se/C-G composite can be attributed to the synergistic combination of carbon black （as the conductive matrix for Se） and the double conductive layer comprising the uniform PANI shell and the graphene sheets, which effectively improves the utilization of selenium and significantly enhances the electronic conductivity of the whole electrode.

Synthesis, Characterization and Electrochemical Study of Graphene Oxide-Multi Walled Carbon Nanotube-Manganese Oxide-Polyaniline Electrode as Supercapacitor

The synthesis of graphene oxide-multi walled carbon nanotube-manganese oxide-polyaniline namely （GMMP） nanocomposite for application in supercapacitor devices was investigated. Morphology of the nanocomposites was studied by X-ray diffraction （XRD）, Fourier transform infrared （FT-IR） spectrosco- py, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and energy dispersive X-ray micmanalysis （EDX）. The electrochemical properties of nanocomposite based electrodes were in- vestigated by cyclic voltammetry （CV）, galvanostatic charge-discharge and electrochemical impedance spectroscopy （EIS） techniques in 0.5 mol/L Na2SO4. The specific capacitances of 173.00, 127.85, 87.50, 58.65 and 12.00 （mF cm^-2） were obtained for GMMP, GMP （GO-MWCNT-PANI）, GMM （GO-MWCNT-MnO2）, GM （GO-MWCNT） and G （GO） at a scan rate of 10 mV s^-1, respectively. Also, GMMP nanocomposite re- tained 90% initial capacitance after 200 cycle of charge-discharge. The good electrochemical response of this nanocomposite is due to the combination of the electrical double layer capacitance of GO and MWCNT and the gradual introduction of pseudo-capacitance through the redox processes of PANI, -COOH, -OH （in MWCNT-COOH, GO-COOH and GO-OH） and MnO2. This revealed the synergistic effect of PANI, MnO2, -OH -COOH on the carbon based support.

SnO_2-Decorated Graphene/Polyaniline Nanocomposite for a High-Performance Supercapacitor Electrode

An SnO2-decorated graphene/polyaniline （GSP） nanocomposite with homogeneous structure was prepared and adopted to achieve high electrochemical performance for supercapacitor electrode. Graphene sheets were decorated with tin dioxide （SnO2） particles, which effectively hinder the restacking of graphene nanosheets, and then were used as substrates for an in-situ polymerization of aniline monomers. The GSP nanocomposite was characterized by field emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared, UV-Visible and X-ray photoelectron spectroscopy. The results revealed that polyaniline nanorods were orderly and vertically aligned on the SnO2-decorated graphene nanosheets via π-π stacking effect between basal planes of graphene nanosheets and phenyl group of polyaniline. The GSP nanocomposite exhibited an excellent specific capacitance of 429 F g^-1 at a current density of 1 A g^-1, excellent cycling stability and rate capability, which suggested a promising application for supercapacitor.

Tunable Enhancement of a Graphene/Polyaniline/Poly(ethylene oxide) Composite Electrospun Nanofiber Gas Sensor

Electrospun nanofibers of a polyaniline(PANi)/(+)-camphor-10-sulfonic acid(HCSA)/poly(ethylene oxide)(PEO)composite doped with different variants of graphene oxide(GO)were fabricated and evaluated as chemiresistor gas sensors operating at room temperature.A new strategy for enhancing PANi/PEO gas sensor performance is demonstrated using GO dopants reduced via thermal(trGO)or chemical(crGO)routes.By varying the chemical reduction duration(6 h,crGO-6 or 24 h,crGO-24),tunable enhancement of sensor response was achieved.Upon exposure to short-chain aliphatic alcohol vapors,the partially reduced crGO-6 dopant exhibited higher response than GO and crGO-24,suggesting that the dopant enhances sensor performance via increased electrical conductivity over neat GO,and enhanced hydrogen bonding capability over the further-reduced crGO-24 variant.Sensor arrays consisting of PANi/PEO doped with trGO,crGO-6 or crGO-24 moieties successfully identified methanol,ethanol,and 1-propanol vapors using principal component analysis(PCA).

Synthesis and Characterization of the Composites of Polyaniline and Graphene Oxide in Situ Polymerization

The novel high-performance nanocomposites of polyaniline (PANI) and graphene oxide sheets (GOs) was synthesized via in situ polymerization in the presence of Hexadecyl trimethyl ammonium Bromide intercalated graphite oxide (CGO), basing on PANI and GOs as a matrix respectively. The result showed that ANI monomer was intercalated into the spacing of CGO, and the CGO was well exfoliated into nanosheets while polymerization. Owing to π–π electron stacking effect between the PANI and the GOs, the electrical conductivity of GOs/PANI nanocomposites (0.47 S/cm), which basing on PANI as a matrix, improved in comparison with pure PANI nanowires (0.02 S/cm) and GO (2.5×10-5 S/cm), while the electrical conductivity of PANI/GOs nanocomposites, which basing on GOs as a matrix, was only 6.2×10-3 S/cm. And it also indicated that the mole ratio of APS, the concentration of HCl, other with the polymerization time, are also important influencing factors of the conductivity of nanocomposites.

Electrochemical Immunosensor for Detection of Atrazine Based on Polyaniline/Graphene

In this study, a novel layer-by-layer polyaniline/graphene （PANi/Gr） structure for electrochemical detec- tion of atrazine was developed. Gr film was synthesized by thermal chemical vapor deposition （CVD） method and transferred onto the PANi-predeposited microelectrode. The properties of PANi/Gr film were thoroughly investigated by high-resolution transmission electron microscopy and Raman techniques. The most attractive feature of this system is a suitable microenvironment, which could provide an amplifi- cation of the conductive signal, thus may contribute to enhancing electron transfer and subsequently improve the sensitivity in electrochemical measurements. With low detection limit （- 43 × 10 -12 g/L）, ac-ceptable stability and good reproducibility, the proposed electrochemical immunosensor could be advantageously extended for multiplexed detection of other agents of environmental pollution.