Fabrication of Transparent,Tough, and Conductive Shape‐Memory Polyurethane Films by Incorporating a Small Amount of High‐Quality Graphene

We report a mechanically strong, electrically and thermally conductive, and optically transparent shape‐memory polyurethane composite which was fabricated by introducing a small amount (0.1 wt%) of high‐quality graphene as a filler. Geometrically large (≈4.6 μm²), but highly crystallized few‐layer graphenes, verified by Raman spectroscopy and transmission electron microscopy, were prepared by the sonication of expandable graphite in an organic solvent. Oxygen‐ containing functional groups at the edge plane of graphene were crucial for an effective stress transfer from the graphene to polyurethane. Homogeneously dispersed few‐layered graphene enabled polyurethane to have a high shape recovery force of 1.8 MPa cm⁻³. Graphene, which is intrinsically stretchable up to 10%, will enable high‐performance composites to be fabricated at relatively low cost and we thus envisage that such composites may replace carbon nanotubes for various applications in the near future.     

Potentiometric Response of Modified Carbon Paste Electrode Based on Mixed Ion‐Exchangers

A new chemically modified carbon paste electrode based on a mixture of two ion‐exchangers namely chlorpheniramine‐silicotungstate (CPM‐ST) and chlorpheniramine‐tetraphenylborate (CPM‐TPB) as ion‐exchange site for determination of chlorpheniramine maleate (CPM) was described. The best performance was exhibited by the electrode having the paste containing 3.0 wt% ion‐exchangers (CPM‐ST&CPM‐TPB), 48.5 wt% graphite, 47.5 wt% DOPh and 1.0 wt% NaTPB. The proposed chemically modified carbon paste electrode exhibited a Nernstian response for CPM over a wide concentration range of 1.2×10^?6 to 1.0×10^?2 M with a detection limit of 5.1×10^?7 M between pH 4.5 and 7.7 with fast response ≤10 s. The sensor showed good selectivity for CPM with respect to a large number of inorganic cations, organic cations, sugars, amino acids and some common drug excipients. The modified electrode was applied to potentiometric determination of CPM in its pharmaceutical preparations and biological fluids (serum and urine) with average recoveries of 97.5–102% and relative standard deviations of 0.32–1.97%.     

A comparative study on the effect of carbon fillers on electrical and thermal conductivity of a cyanate ester resin

Carbon fillers including multi-walled carbon nanotubes (MWCNTs), carbon black (CB) and graphite were introduced in a cyanate ester (CE) resin, respectively. The effects of the fillers on the electrical and thermal conductivity of the resin were measured and analyzed based on the microscopic observations. MWCNTs, CB and graphite exhibited percolation threshold at 0.1 wt%, 0.5 wt% and 10 wt%, respectively. The maximal electrical conductivity of the composites was 1.08 S/cm, 9.94 × 10⁻³ S/cm and 1.70 × 10⁻⁵ S/cm. MWCNTs showed the best enhancement on the electrical conductivity. The thermal behavior of the composites was analyzed by calorimetry method. Incorporation of MWCNTs, CB and graphite increased the thermal conductivity of CE resin by 90%, 15% and 92%, respectively. Theoretical models were introduced to correlate the thermal conductivity of the CE/MWCNTs composite. The interfacial thermal resistance between CE resin and MWCNTs was 8 × 10⁻⁸ m²K/W and the straightness ratio was 0.2. The MWCNTs were seriously entangled and agglomerated. Simulation results revealed that thermal conductivity of the CE/MWCNTs composites can be substantially elevated by increasing the straightness ratio and/or filler content of MWCNTs.     

聚并苯纳米颗粒与聚丙烯复合制备新型抗静电阻燃材料

用聚并苯纳米颗粒作为新型导电填料代替导电炭黑和石墨等, 制备出具有抗静电阻燃性能的纳米聚并苯/聚丙烯复合材料. 测定了复合材料的渗流转变区, 讨论了纳米聚并苯含量对复合材料体积电阻率和表面电阻率的影响. 实验结果表明, 所制备复合材料的渗流转变发生在纳米聚并苯质量分数为16.7%-28.6%范围内, 当纳米聚并苯含量为28.6%时, 体积电阻率下降至2.09×107 Ω·cm. 另外, 阻燃性能研究结果表明, 当纳米聚并苯质量分数为23.1%时, 复合材料在空气中可以自熄, 因而可应用于矿井中抗静电阻燃塑料管道.     

新型软质抗静电聚氯乙烯材料的研究

合成了一种长链季铵盐类化合物, 将其用作抗静电剂添加到软质聚氯乙烯(PVC)材料中, 测试了材料的表面电阻、力学性能, 并采用扫描电子显微镜测试研究了其结构. 结果表明: 随合成长链季铵盐的添加量增大, PVC材料的表面电阻率降低, 较小的添加量(4.5%)即可使材料的表面电阻率降低至3.0×10⁸ Ω以下, 达到了煤矿行业对高分子材料抗静电性能的要求. 在上述抗静电PVC材料中添加一定量的聚氧化乙烯(PEO), 可以降低抗静电材料对环境湿度的依赖性, 并提高PVC材料的力学性能和抗静电性能.     

Electrochemical Determination of the KRAS Genetic Marker for Colon Cancer with Modified Graphete and Graphene Paste Electrodes

The determination of KRAS was performed using electrochemical sensing devices based on graphite and graphene pastes, modified with a phthalocyanine-boron dipyrromethene (BODIPY) and azulenes dyes. The limits of quantification for KRAS were 1.54?×?10^?4?µg/mL using the sensor based on the phthalocyanine-BODIPY dye and graphite, 2.64?×?10^?7?µg/mL using the sensor based on 2,6-bis((E)-2-(furan-2-yl)vinyl)-4-(4,6,8-trimethylazulen-1-yl)pyridine/TiO₂Pt/reduced graphene oxide, and 3.84?×?10^?3?µg/mL using the sensor based on 2,6-bis((E)-2-(thiophen-3-yl)vinyl)-4-(4,6,8-trimethylazulen-1-yl)pyridine/TiO₂Pt/reduced graphene oxide. Recovery measurements demonstrated the suitable analytical performance of these sensors for the early detection of colon cancer by the analysis of whole blood samples.     

Graphene Oxide/ZnO Nano Composite for Sensitive and Selective Electrochemical Sensing of Levodopa and Tyrosine Using Modified Graphite Screen Printed Electrode

Determination of levodopa and tyrosine as two important species for treatment of Parkinson's disease is described. A novel electrochemical sensor involving graphene oxide/ZnO nanorods (GR/ZnO) nano composite and the graphite screen‐printed electrodes (GSPE) was developed for the simultaneous detection of levodopa and tyrosine. The screen‐printed electrodes with several advantages, including low cost, versatility and miniaturization were employed. On the other hand, the graphene oxide/ZnO nanorods nano composite was casted on the surface of GSPE to obtain GR/ZnO/SPE. The proposed nano sensor has excellent performance such as high sensitivity, good selectivity and analytical application in real samples. The combination of graphene oxide/ZnO nanorods nano composite with the screen‐printed electrode is favorable for amplifying electrochemical signals. Under optimized conditions square wave voltammetry (SWV) exhibited linear dynamic ranges from 1.0×10^?6 to 1.0×10^?3 M and 1.0×10^?6 to 8.0×10^?4 M with detection limits of 4.5×10^?7 M and 3.4×10^?7 M for levodopa and tyrosine respectively.     

A comparative study of chromium(III) ion-selective electrodes based on N,N-bis(salicylidene)-o-phenylenediaminatechromium(III)

A comparative study was made between three types of Cr(III) ion-selective electrodes: PVC membrane electrode, silver coated electrode and modified carbon paste electrode based on N,N-bis(salicylidene)-o-phenylenediaminatechromium(III) complex (Crsalophen). As anticipated, electrodes with a solid contact, rather than a traditional liquid inner contact, give lower detection limits because of diminished ion fluxes. Often, however, ill-defined solid contact gives rise to instabilities and interferences by oxygen gas. The carbon paste electrode provides a more sensitive and stable device than that afforded by PVC and coated electrodes. The best performance was obtained by an electrode based on the paste containing 3.5 wt% Cr-complex, 48.5% graphite plasticized with a mixture of 24.0 wt% tris(2-ethylhexyl) phosphate (DOPh) + 24.0 wt% dioctyl sebacate (DOS). The sensor has a linear dynamic range of 7.5 × 10^-6 to 1.0 × 10^-2 M, with a Nernstian slope of 20.1 ± 0.6 mV decade^-1, and a detection limit of 1.8 × 10^-6. It has a short response time of a bout 8 s and is applicable in a pH range of 4.5-7.7. It was successfully used as an indicator electrode in potentiometric titration of Cr(III) with EDTA and in determination of Cr(III) in water samples and chromium in (Crsalophen).     

Insights into electrocatalytic activity of epitaxial graphene on SiC from cyclic voltammetry and ac impedance spectroscopy

Electrocatalytic activity of graphene grown epitaxially on SiC is studied using cyclic voltammetry and electrochemical impedance spectroscopy. AFM images show step-like topography of SiC-graphene. For ferri-/ferrocyanide redox couple, no voltammetric response is observed at the pristine graphene. Basal planes of graphite are electrochemically inactive as well. After electrochemical oxidation, apparent redox peaks appear at both the graphene and graphite electrode. However, more intensive redox peaks are observed at graphene, where simultaneous redox reaction with the adsorbed and the diffused ferri-/ferrocyanide ions occurs. Electrochemical impedance measurements show that the graphene electrode behaves like an array of microelectrodes. We used the partially blocked electrode model to fit impedance data. Using the fitting parameters, a size of microelectrodes was found to be 23.8?±?2.1 μm and the active surface of graphene was estimated to be 21 %. A value of the standard electron transfer rate constant found for the anodized epitaxial graphene (2.16?±?0.32)?×?10^??3cm???s^??1) is by one order of magnitude lower than the standard rate constant estimated for the anodized graphite basal planes (～5?×?10^??2cm???s^??1). Electrochemical reduction causes total disappearance of electrochemical responses at the graphene electrode, whereas only slight decrease of the peak currents is observed at the reduced graphene. Such behavior proves that different activation mechanisms occur at the graphene and graphite electrodes.     

Comparisons Among Electrical and Rheological Properties of Melt-Mixed Composites Containing Various Carbon Nanostructures

The present investigation compares different carbon-based nanoscaled materials with regard to their effectiveness in producing thermoplastic polymers with antistatic and electrically conductive behavior. The dispersed phases are carbon black (CB) as spherical particles, multiwalled carbon nanotubes (MWNT) as fiber-like filler, and expanded graphite (EG) as platelet-like filler. Each was incorporated into polycarbonate by small-scale melt mixing. The electrical percolation concentrations were found to be 2 wt% for MWNT, 4 wt% for EG, and 8.75 wt% for CB which parallels the aspect ratios of the fillers. For EG a strong dependence of morphology and electrical resistivity on mixing time was observed, indicating a structural change/destruction during intensive shear mixing. Rheological percolation thresholds were found to be lower than electrical percolation threshold for the MWNT and CB, but similar in the case of EG. The general impact on complex melt viscosity decreases in the order MWNT, CB, EG. For EG, at higher loadings (above 4wt%) the viscosity increase with filler content is delayed as is the decrease in resistivity.     

Flexible poly(dimethyl siloxane) composites enhanced with 3D porous interconnected three-component nanofiller framework for absorption-dominated electromagnetic shielding

A new poly(dimethyl siloxane) (PDMS) composite was developed based on the 3D porous interconnected framework that is fabricated from reduced graphene oxide (rGO) and Dy₂O₃ decorated single-walled carbon nanotube (Dy₂O₃@SWNT). Despite merely containing ~0.6 wt% fillers, the composite prepared by backfilling 3D framework (3D-Dy₂O₃@SWNT-rGO) with PDMS prepolymer acquires as high as 32.9 dB of absorption-dominated (92.3%–96.9%) electromagnetic interference (EMI) shielding effectiveness in X-band, and up to 47% and 52% increments of respective compressive strength and modulus at 50% strain relative to PDMS. These performances result from the excellent combination of electrical conductivity (up to 0.317 S cm⁻¹), magnetism (up to 7.1 × 10⁻⁵ emu g⁻¹ of susceptibility), and mechanical toughness (complete recovery after 80% compression) in a single three-component filler system of 3D-Dy₂O₃@SWNT-rGO. Moreover, the organic integration of mechanical flexibility of PDMS with shape-tunable ability of 3D-Dy₂O₃@SWNT-rGO enables PDMS composites developed here to EMI-shield any shape surfaces.     

Synthesis of non‐destructive amido group functionalized multi‐walled carbon nanotubes and their application in antistatic and thermal conductive polyetherimide matrix nanocomposites

Thermal conductive and antistatic polyetherimide (PEI) nanocomposites were fabricated by encapsulating non‐destructive amido group functionalized multi‐walled carbon nanotubes (MWCNTs) into the PEI matrix. Briefly, nearly half of acyl chloride groups in poly (acryloyl chloride) reacted with sodium azide and formed acyl azide groups, which could conjunct with MWCNTs via non‐destruction nitrenes addition reaction. The remaining acyl chloride groups in poly (acryloyl chloride) hydrolyzed into carboxyl groups, therefore COOH‐rich MWCNTs (MWCNTs@azide polyacrylic acid) were synthesized without serious damage to the MWCNTs. Then, MWCNTs@azide polyacrylic acid were then reacted with p‐Phenylene diamine (PPD) and transformed to amido group functionalized MWCNTs (MWCNTs@PPD). MWCNTs@PPD could participate into the in situ polymerization of PEI matrix, where the conjunction between bisphenol A dianhydride and amido groups on MWCNTs@PPD guaranteed the strong covalent bonding at the PEI/MWCNTs interface, which directly avoided the aggregation of MWCNTs. Owing to the non‐destructive modification of MWCNTs and tight matrix/filler interface, the volume electric and thermal conductivity of as‐prepared nanocomposites was up to 6.4 × 10^?8 S/cm (1.0 wt%, MWCNTs@PPD) and 0.43 W/(m · K) (4.0 wt%, MWCNTs@PPD), respectively. Copyright © 2016 John Wiley & Sons, Ltd.     

Influence of barium titanate nanofiller on PEO/PVdF-HFP blend-based polymer electrolyte membrane for Li-battery applications

Organic-inorganic hybrid membranes based on poly(ethylene oxide) (PEO) 6.25 wt%/poly(vinylidene fluoride hexa fluoro propylene) [P(VdF-HFP)] 18.75 wt% were prepared by using various concentration of nanosized barium titanate (BaTiO₃) filler. Structural characterizations were made by X-ray diffraction and Fourier transform infrared spectroscopy, which indicate the inclusion of BaTiO₃ in to the polymer matrix. Addition of filler creates an effective route of polymer-filler interface and promotes the ionic conductivity of the membranes. From the ionic conductivity results, 6 wt% of BaTiO₃-incorporated composite polymer electrolyte (CPE) showed the highest ionic conductivity (6 × 10^?3 Scm^?1 at room temperature). It is found that the filler content above 6 wt% rendered the membranes less conducting. Morphological images reveal that the ceramic filler was embedded over the membrane. Thermogravimetric and differential thermal analysis (TG-DTA) of the CPE sample with 6 wt% of the BaTiO₃ shows high thermal stability. Electrochemical performance of the composite polymer electrolyte was studied in LiFePO₄/CPE/Li coin cell. Charge-discharge cycle has been performed for the film exhibiting higher conductivity. These properties of the nanocomposite electrolyte are suitable for Li-batteries.     

Polymeric membrane and coated graphite electrode based on newly synthesized tetraazamacrocyclic ligand for trace level determination of nickel ion in fruit juices and wine samples

Novel polymeric membrane electrode (PME) and coated graphite electrode (CGE) for nickel ion were prepared based on 2,9-(2-methoxyaniline)₂-4,11-Me₂-[14]-1,4,8,11-tetraene-1,5,8,12-N₄ as a suitable neutral ionophore. The addition of lipophilic anion excluder (NaTPB) and various plasticizers viz o-nitrophenyloctylether (o-NPOE), dioctylphthalate (DOP), dibutylphthalate (DBP), 1-chloronaphthalene (CN) and tri-n-butylphosphate (TBP) have found to improve the performance of the sensors. The best performance was obtained for the membrane sensor having a composition of I:NaTPB:TBP:PVC in the ratio 6:4:100:90 (w/w; mg). The electrodes exhibit Nernstian slopes for Ni²⁺ ions over wide concentration ranges of 4.6 × 10^?7–1.0 × 10^?1 M for PME and 7.7 × 10^?8–1.0 × 10^?1 M for CGE with limits of detection of 2.7 × 10^?7 M for PME and 3.7 × 10^?8 M for CGE. The response time for PME and CGE was found to be 10 and 8 s respectively. The potentiometric responses are independent of the pH of the test solution in the pH range 3.0–8.0. The proposed electrodes revealed good selectivities over a wide variety of other cations including alkali, alkaline earth, transition and heavy metal ions. The coated graphite electrode was used as an indicator electrode in the potentiometric titration of nickel ion with EDTA and in direct determination in different fruit juices and wine samples.     

Division Electrosynthesis of Palladium Nanomaterials with Copper–Graphene as Sacrificial Templates and Its Application for Hydrazine Sensing

One‐pot electrodeposited copper‐graphene (Cu‐GE ) nanocomposite acting as sacrificial template for the division electrosynthesis of palladium nanoparticles (PdNPs ) on pyrolytic graphite electrode (PGE ) was synthesized. The designed PdNPs‐GE nanocomposite was evaluated as a new material for highly sensitive determination of hydrazine (N₂H₄ ). Scanning electron microscopy revealed that the PdNP‐GE ‐modified PGE had uniform morphology. The results of energy‐dispersive X‐ray spectrograms confirmed the ingredients of the division electrosynthesis process. Electrochemical experiments were performed to characterize the sensing properties of PdNPs‐GE toward the electrocatalytic oxidation of N₂H₄ at 0.20 V in sodium phosphate buffered saline (0.1 M pH 7.0). The sensor showed fast response (<3 s), high sensitivity [398 (1 × 10⁻⁶ A) (1 × 10⁻³ M)⁻¹], and broad linearity in the range 2.5 × 10⁻⁸–2.7 × 10⁻⁴ M with a relatively low detection limit of 1.0 × 10⁻⁸ M (S/N = 3).     

Molecularly Imprinted Electrochemical Sensor Based on Modified Reduced Graphene Oxide‐gold Nanoparticles‐polyaniline Nanocomposites Matrix for Dapsone Determination

This work was designed to develop an electrochemical sensor based on molecular imprinted polyaniline membranes onto reduced graphene oxide (RGO) and gold nanoparticles (AuNPs) modified glassy carbon (GC) electrode for dapsone (DDS) determination. The prepared RGO/AuNPs/PANI‐MIPs nanocomposite was characterized by Ultra‐Violet‐Visible (UV‐Vis), Fourier transform infrared spectroscopy (FT‐IR) and scanning electronic microscopy (SEM) images. The feature of the imprinted electrode was evaluated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and impedance spectroscopy (IS). Throughout this study several analytical parameters, such as incubation time, pH value, concentration of monomer/template molecules and electro‐polymerization cycles were investigated. Under the optimized conditions, the experimental results showed best analytical performances for DDS detection with a sensitivity of 0.188 Ω/mol L^?1, a linear range from 1.0×10^?7 M to 1.0×10^?3 M and a detection limit of 6.8×10^?7 M. The bioanalytical sensor was applied to the determination of dapsone in real samples with high selectivity and recovery.     

Electrochemical Behavior and Determination of Rutin at the Copper Nanoparticles-Doped Zeolite A/Graphene Oxide-Modified Electrode

In this work, a novel Cu?zeolite A/graphene modified glassy carbon electrode was applied for the determination of rutin. The Cu?zeolite A/graphene composites were prepared using copper doped zeolite A and graphene oxide as the precursor, subsequently reduced by chemical agents. Based on the Cu?zeolite A/graphene modified electrode, the overpotential of the rutin oxidation was lowered by ~300 mV. Also the proposed Cu?zeolite A/graphene modified electrode showed higher electrocatalytic performance than zeolite A/graphene electrode or graphene modified electrode. The electrochemical behavior of copper incorporated in the zeolite A modified electrode illustrated the adsorption-controlled reaction at the modified electrode. The behavior of electrocatalytic oxidation of rutin at the modified electrode was investigated. The diffusion coefficient of rutin was equal to 4.2 × 10^–7 cm²/s. A linear calibration graph was obtained for rutin over the concentration range of 2.3 × 10^–7–2.5 × 10^–3 M. The detection limit for rutin was 1.2 × 10^–7 M. The RSDs of 10 replicate measurements performed on a single electrode at rutin concentrations between 2.3 × 10^–7–2.5 × 10^–3 M were between 1.1 and 2.1%. Study of the influence of potentially interfering substances on the peak current of rutin showed that the method was highly selective. The proposed electrode was used for the determination of rutin in real samples with satisfactory results.     

Nanobiocomposite Modified Carbon‐Ceramic Electrode Based on Nano‐TiO2‐Plant Tissue and Its Application for Electrocatalytic Oxidation of Dopamine

A new modified carbon‐ceramic electrode was prepared by incorporating TiO₂ nanoparticle into sol‐gel network by accompanying apple tissue. A mixture of fine graphite powder with 15 wt% of TiO₂ nanoparticle was used for the preparation of the carbon matrix and finally modification with a known amount weighted of apple tissue. The apple tissue containing polyphenol oxidase enzyme acts as molecular recognition element. The electrocatalytic oxidation of dopamine was investigated on the surface of the nanobiocomposite modified carbon‐ceramic electrode using cyclic voltammetry, chronoamperometry and amperometry techniques. Effect of pH, scan rate, TiO₂ percentage on the response of modified electrode was studied. The prepared modified electrode presented a linear range for dopamine from 5.0×10^?6 to 1.2×10^?3 M in buffered solutions with pH 7.4 by amperometry. The detection limit was 3.41×10^?6 M dopamine. The response of the modified carbon‐ceramic electrode and unmodified carbon‐ceramic electrode was compared.     

Electroless Ni–P coated on graphite as catalyst for the electro-oxidation of dextrose in alkali solution

Graphite particles were coated with Ni–P by electroless deposition using a conventional bath consisting of a nickel salt and hypophosphite. After 15 min of electroless deposition, the graphite particles were covered with 10 wt% nickel and 0.7–1.0 wt% phosphorus as analysed by wet chemical method. Surface morphology was studied by scanning electron microscopy (SEM). Electrochemical characterisation for the catalytic activity was done by cyclic voltammetry. Pure Ni powder and electroless Ni–P coated on graphite were used as catalysts for the electro-oxidation of dextrose (1.8 × 10⁻³ to 4.5 × 10⁻³ M) in 0.1 M KOH solution. Comparative studies revealed that electroless Ni–P coated on graphite particles acted as a better catalyst than pure Ni powder for catalytic reaction.     

Electrochemical Investigations of the Anticancer Drug Idarubicin Using Multiwalled Carbon Nanotubes Modified Glassy Carbon and Pyrolytic Graphite Electrodes

The effect of surface modifications on the electrochemical behavior of the anticancer drug idarubicin was studied at multiwalled carbon nanotubes modified glassy carbon and edge plane pyrolytic graphite electrodes. The surface morphology of the modified electrodes was characterized by scanning electron microscopy. The modified electrodes were constructed for the determination of idarubicin using adsorptive stripping differential pulse voltammetry. The experimental parameters such as supporting electrolyte, pH, accumulation time and potential, amount of carbon nanotubes for the sensitive assay of idarubicin were studied as details. Under the optimized conditions, idarubicin gave a linear response in the range 9.36×10^?8–1.87×10^?6 M for modified glassy carbon and 9.36×10^?8–9.36×10^?7 M for modified edge plane pyrolytic graphite electrodes. The detection limits were found as 1.87×10^?8 M and 3.75×10^?8 M based on modified glassy carbon and edge plane pyrolytic graphite electrodes, respectively. Interfering species such as ascorbic acid, dopamine, and aspirin showed no interference with the selective determination of idarubicin. The analyzing method was fully validated and successfully applied for the determination of idarubicin in its pharmaceutical dosage form. The possible oxidation mechanism of idarubicin was also discussed. The results revealed that the modified electrodes showed an obvious electrocatalytic activity toward the oxidation of idarubicin by a remarkable enhancement in the current response compared with bare electrodes.