Conducting polymer composites of polyvinylferrocene and polypyrrole (PVF/PPy) were synthesized chemically by the in situ polymerization of pyrrole in the presence of PVF using FeCl3 as oxidant. Acetic (CH3COOH) and boric (H3BO3) acids were used as the synthesis medium. Effects of the synthesis medium on the properties of the PVF/PPy composite were investigated. The PVF/PPy composites and homopolymers were characterized by fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and magnetic susceptibility techniques. Conductivity measurements were performed using the four‐probe technique. We found that the conductivities of PVF/PPy‐H3BO3 (1.19 S cm?1) and PVF/PPy‐CH3COOH (4.5×10?1 S cm?1) increased relative to those of the homopolymers of PPy‐H3BO3 (2.1×10?2 S cm?1) and PPy‐CH3COOH (1.2×10?2 S cm?1) due to the interaction of PVF with the pyrrole moiety. The stability of all homopolymers and composites were investigated by thermogravimetric analysis and by conductivity measurements during heating‐cooling cycles. There was a small drop in conductivity caused by the annealing of PVF/PPy composites at 70°C. The conductivity of all samples increased with temperature and exhibited stable electrical behavior with increasing temperature. TGA analysis of samples showed that the composites were more stable than the homopolymers or PVF separately. The magnetic susceptibility values of samples were negative, except for PVF/PPy‐H3BO3. Morphology changes of the composites investigated by scanning electron microscopy (SEM), attributed to synthesis conditions, have a significant effect on their conductivity. 相似文献
We show that the onset pressure for appreciable conductivity in layered copper‐halide perovskites can decrease by ca. 50 GPa upon replacement of Cl with Br. Layered Cu–Cl perovskites require pressures >50 GPa to show a conductivity of 10?4 S cm?1, whereas here a Cu–Br congener, (EA)2CuBr4 (EA=ethylammonium), exhibits conductivity as high as 2×10?3 S cm?1 at only 2.6 GPa, and 0.17 S cm?1 at 59 GPa. Substitution of higher‐energy Br 4p for Cl 3p orbitals lowers the charge‐transfer band gap of the perovskite by 0.9 eV. This 1.7 eV band gap decreases to 0.3 eV at 65 GPa. High‐pressure X‐ray diffraction, optical absorption, and transport measurements, and density functional theory calculations allow us to track compression‐induced structural and electronic changes. The notable enhancement of the Br perovskite's electronic response to pressure may be attributed to more diffuse Br valence orbitals relative to Cl orbitals. This work brings the compression‐induced conductivity of Cu‐halide perovskites to more technologically accessible pressures. 相似文献
An electrochemical method for the determination of tripelennamine hydrochloride (TPA) using cetyltrimethylammoniumbromide‐multiwalled carbon nanotubes modified glassy carbon electrode (MWCNT‐CTAB/GCE) was developed. Because of good electrical conductivity of MWCNT and catalytic behavior of CTAB, new electrode significantly enhances the sensitivity for the detection of TPA. Parameters such as amount of modifier suspension, scan rate, pH of measure solution, heterogeneous rate constant were investigated. The electrode exhibits a linear potential response in the range of 1.0×10?8 M to 3.0×10?6 M with a detection limit of 2.38× 10?9 M. The modified electrode was successfully applied to the determination of TPA in pharmaceutical and real samples. 相似文献
A graphite electrode modified with silver (Ag‐CPE) has been applied to detect mercury(II) using differential pulse voltammetry (DPV). Under optimized conditions, the calibration curve is linear in the range from 5.0×10?8 mol L?1 to 1.0×10?4 mol L?1 of mercury(II). The detection limit was found to be 3.38×10?8 mol L?1 with a relative standard deviation (RSD) of 2.25 % (n=8). The proposed method was successfully applied for the detection of mercury(II) in leachate samples. The Ag‐CP composites were characterized using X‐ray diffraction (XRD), BET adsorption analysis and scanning electron microscopy (SEM). 相似文献
The ionic conductivity properties of the face‐centered cubic [Ni8(OH)4(H2O)2(BDP_X)6] (H2BDP_X=1,4‐bis(pyrazol‐4‐yl)benzene‐4‐X with X=H ( 1 ), OH ( 2 ), NH2 ( 3 )) metal–organic framework (MOF) systems as well as their post‐synthetically modified materials K[Ni8(OH)5(EtO)(BDP_X)5.5] ( 1@KOH , 3@KOH ) and K3[Ni8(OH)3(EtO)(BDP_O)5] ( 2@KOH ), which contain missing‐linker defects, have been studied by variable temperature AC impedance spectroscopy. It should be noted that these modified materials exhibit up to four orders of magnitude increase in conductivity ‐values in comparison to pristine 1 – 3 systems. As an example, the conductivity value of 5.86×10?9 S cm?1 (activation energy Ea of 0.60 eV) for 2 at 313 K and 22 % relative humidity (RH) increases up to 2.75×10?5 S cm?1 (Ea of 0.40 eV) for 2@KOH . Moreover, a further increase of conductivity values up to 1.16×10?2 S cm?1 and diminution of Ea down to 0.20 eV is achieved at 100 % RH for 2@KOH . The increased porosity, basicity and hydrophilicity of the 1@KOH – 3@KOH materials compared to the pristine 1 – 3 systems should explain the better performance of the KOH‐modified materials. 相似文献
Abstract Enantioselective, potentiometric membrane electrodes (EPMEs) based on antibiotics are proposed for the enantioanalysis of L‐vesamicol. A carbon paste was modified with antibiotics (vancomycin, teicoplanin, and teicoplanin modified with acetonitrile), as chiral selectors. The EPMEs based on antibiotics were reliably used for enantiopurity tests of L‐vesamicol using the direct potentiometric technique. The following linear concentration ranges: 1.0×10?6–1.0×10?4, 1.0×10?6–1×10?3 and 1×10?7?1×10?2 mol/L; and detection limits: 1.1×10?7, 9.6×10?8, and 3.6×10?8 mol/L were determine for vancomycin, teicoplanin, and teicoplanin modified with acetonitrile–based EPMEs, respectively. The proposed EPMEs were applied for the enantioanalysis of L‐vesamicol in urine samples. 相似文献
ABSTRACT Materials which display ionic conductivity were produced by the sol-gel and microemulsion-gel methods. The charging and discharging characteristics were investigated and it was found that a single ionic species was responsible for the conduction, the ionic species being residual protons from the initial component mixture. The complex impedence of various samples was measured and the ionic conductivities ranged in value from 9 × 10?8 to 1 × 10?5 ohm?1 cm?1. An Arrhemius plot for a microemulsion-gel revealed that the energy of activation was 0.15 eV. 相似文献
The electrical conductivity of composites of exfoliated graphite nanoplatelets (GNPs), including bromine‐doped GNP, and conjugated polyacrylonitrile has been investigated. The focal point is the dual nature of the graphite nanoparticles, which exhibit both intrinsic electrical conductivity and doping capability of semi‐conductive polymers such as conjugated polyacrylonitrile to form charge‐transfer complexes. The conductivity is particularly enhanced in conjugated polyacrylonitrile composites (e.g., with 6 wt.‐% graphite nanoplatelets) where the value rises from 1 × 10−10 to 2 × 10−3 S · cm−1, which reflects jointly the conductivity of the doped semi‐conductive polymer together with the percolation‐based conductivity of the particles.
This paper describes a rapid and sensitive method for determination of the hair dye Basic Blue 41 in wastewater samples using screen‐printed carbon electrodes modified with graphene (SPCE/Gr). The method is based on the reversible reduction of azo groups of the dye at potential of ?0.23 V/?0.26 V, where both the anodic and cathodic currents increased 1,300 % when compared to screen‐printed carbon (SPCE) and glassy carbon electrodes (GCE). The optimization of a square wave voltammetric method was performed by means of 23 factorial design, Doehlert matrix and multi‐response assays, and the best parameters were: frequency (54.8 Hz), step potential (6 mV), pulse amplitude (43.7 mV) and pH 4.5. The analytical curve was constructed from 3.00×10?8 to 2.01×10?6 mol L?1, with detection and quantification limits of 5.00×10?9 and 1.70×10?8 mol L?1, respectively. The repeatability of the method evaluated for 10 consecutive measurements at concentrations of 1.70×10?7 mol L?1 and 1.70×10?6 mol L?1, showed relative standard deviation of 3.56 and 0.57 %, respectively. The sensor based in SPCE/Gr was successfully applied in wastewater samples collected from a drinking water treatment plant and validated by comparison with HPLC‐DAD method with good accuracy. 相似文献
A highly stable proton conductor has been developed from carbon sphere oxide (CSO). Carbon sphere (CS) generated from sucrose was oxidized successfully to CSO using Hummers’ graphite oxidation technique. At room temperature and 90 % relative humidity, the proton conductivity of thin layer CSO on microsized comb electrode was found to be 8.7×10?3 S cm?1, which is higher than that for a similar graphene oxide (GO) sample (3.4×10?3 S cm?1). The activation energy (Ea) of 0.258 eV suggests that the proton is conducted through the Grotthuss mechanism. The carboxyl functional groups on the CSO surface are primarily responsible for transporting protons. In contrast to conventional carbon‐based proton conductors, in which the functional groups decompose around 80 °C, CSO has a stable morphology and functional groups with reproducible proton conductivity up to 400 °C. Even once annealed at different temperatures at high relative humidity, the proton conductivity of CSO remains almost unchanged, whereas significant change is seen with a similar GO sample. After annealing at 100 and 200 °C, the respective proton conductivity of CSO was almost the same, and was about ~50 % of the proton conductivity at room temperature. Carbon‐based solid electrolyte with such high thermal stability and reproducible proton conductivity is desired for practical applications. We expect that a CSO‐based proton conductor would be applicable for fuel cells and sensing devices operating under high temperatures. 相似文献
A simplified design of thermal lens apparatus is presented in which a chopped cw argon laser beam produces a transient thermal lens in a cylindrical gas cell. The axial intensity variation of a cw helium-neon laser probing this lens is analysed to yield the thermal diffusivities and thus the thermal conductivity coefficients of Kr, CO2, CH4, C2H6, C3H8, C3H6 and C4H10 as 9.4 × 10?3 ± 4%, 1.6 × 10?2 ± 3%, 2.98 × 10?2 ± 4%, 2.03 × 10?2 ± 4%, 2.05 × 10?2 ± 7%, 1.6 × 10?2 ± 8% and 1.9 × 10?2 ± 8% respectively in W m?1 K?1 at 300 K. The method is rapid, requiring only that the sample be transparent at both laser frequencies used. A simplified mathematical analysis is shown to be adequate for this system. For the conditions specified, self-lensing of the argon laser beam is shown to be compensated by using an effective laser beam diameter. 相似文献