The specific features of charge carrier transport in poly(N-vinylcarbazole) films doped with single-wall carbon nanotubes have been investigated. The mobilities of electrons and holes in ITO-polymer composite-Al samples have been determined by the time-of-flight method and by measuring the voltage-current characteristics of steady-state currents. According to the time-of-flight experiments, in the films of a poly(N-vinylcarbazole)-0.26 wt % single-wall carbon nanotubes composite, the drift mobility of electrons lies within (1.2–4.5) × 10?6 cm2/(V s) and exceeds the mobility of holes by a factor of 5. The shape of the transient current suggests the dispersion character of transport of electrons and holes. With an increase in the concentration of single-wall nanotubes from 0.26 to 0.43 wt %, the conductivity of the composite films increases by two orders of magnitude; that is, the threshold of conductivity percolation has been achieved. A simple model is proposed to describe the transport of charge carriers in the polymer system under study. 相似文献
The photoelectric, nonlinear optical, and photorefractive characteristics of polymer composites made from unplasticized polyvinylcarbazole (PVK) and single-wall carbon nanotubes containing surface oxygen groups (at C:O ratio of 77.8:22.2%) were analyzed. The dependences of the quantum efficiency of charge-carrier generation on the applied electric field E measured at 1064 and 1550 nm coincide and are approximated by the Onsager equation expanded to the E4 term, at π0 = 0.012 and r0 = 9.8 Å. The third-order optical nonlinearity determined by the EFISH technique at a nanotube content of 0.26 wt % is 2 × 105 pm2/V2 or 2.3 × 10?29 C4 m/J3 in SI units. The pattern of photorefractive kinetic curves indicates that the mean free path of holes is longer than the mean range of electrons. The photorefractive net gain coefficient of the signal beam measured at 1064 nm in a field of E = 170 V/μm is Γ ? α = 55 cm?1 (α = 10 cm?1 is the optical absorption coefficient at 1064 nm). At 1550 nm, the net gain coefficient measured in a field of E = 265 V/μm is Γ ? α = 55.7 cm?1 (α = 3.3 cm?1 at 1550 nm). In the presence of oxygen groups, there is no transfer of electrons photogenerated in carbon nanotubes to the external acceptor C60. This effect can be associated with an increase in the ionization potential of nanotubes by almost 0.8 eV as a result of oxidation. 相似文献
(N-Ethylcarbazol-3-yl)methyl acrylate and methacrylate were polymerized anionically and radically. Anionically-polymerized polyacrylate using ethylmagnesium chloride-benzalacetophenone as catalyst is an isotactic rich polymer with 85% isotactic dyad. All polymers except anionically polymerized polymethacrylate showed good film forming property. Hole drift mobilities measured by the time-of-flight method at room temperature and at 5 × 105 V/cm are in the following order: isotactic polyacrylate (1.0 × 10-5 cm2/V s) > atactic polyacrylate (1.8 × 10-6 cm2/V s) > atactic polymethacrylate (1.2 × 10-6 cm2/V s) at 5 × 105 V/cm. These results are discussed in terms of the hopping model between localized sites. 相似文献
The processes of generation and transport of excess charge carriers in polyvinylcarbazole at room temperature and at 353 K were experimentally studied. The polymer was charged with pulses of electrons at energies of 7 and 50 keV, which differed in both linear energy transfer and track structure. A universal method of investigation based on the combination of the time-of-flight technique in the both (surface and bulk) modes with the measurement of radiation-induced conductivity was used. The radiation-chemical yield of free charges was measured using two independent procedures. It was shown that the radiation chemical yield of free charges at 293 K was somewhat smaller for 7-keV than for 50-keV electrons; in the latter case, G = 1.1 in an electric field of 2 × 107 V/m. The parameters of the generalized physical model were determined for polyvinylcarbazole. 相似文献
A simple and fast voltammetric method based on a new electrode composed of carbon paste electrode/bifunctional hybrid ion imprinted polymer (CPE/IIP) was developed for the quantification of Cd2+ in water samples. The voltammetric measurements by Differential Pulse Voltammetry were performed by using CPE containing 11.0 mg of IIP under phosphate buffer solution at concentration 0.1 mol L?1 and pH 6.5. The electrochemical method was carried out by Cd2+ preconcentration at ?1.2 V during 210 s, followed by anodic stripping. The performance of IIP towards Cd2+ determination was evaluated by comparison to non-imprinted polymer, whose detectability of IIP was much higher (45%). The sensitivity of the sensor was found to be 0.0105 µA/µg L?1. The limits of detection and limits of quantification were found to be 4.95 μg L?1 and 16.4 μg L?1, respectively. The developed method was successfully applied to Cd2+ determination in mineral, tap and lake water samples, whose results are in agreement with thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) used as reference analytical technique. According to achieved results, the developed method can be used for routine analysis of quality control of water samples from different sources. 相似文献
μd,h-μ-Carboxilato-e-μ-methoxo-f-μ-oxo-bis[trichloroantimony(V)]. Preparation and Spectra The preparation of the unknown d,h-μ-carboxilato-e-μ-methoxo-f-μ-oxo-bis[trichloroantimony(V)] compounds is described (CF3COO ? 2 , CH3CH2COO ? 4 ). The vibrational spectra of 2 and 4 were assigned and compared with those of the corresponding hydroxo compounds 1 and 3 . The mass spectra of 1—4 are measured and the fragmentation pathes are proposed. The formulae of some fragments of 1 with m/e values greater than the molecular weight were determined by high resolution. 相似文献
In-situ FT-IR spectra were taken during a cyclic voltammetric study of polythiophene in 1M LiClO4 in propylene carbonate. The external reflection technique was used in the spectroscopic measurements. A broad band extending from 1500 cm–1 to higher wave numbers appeared during oxidation of polythiophene with a potential scan from 2.8 V to 4.2 V. Bands due to doping of the polymer at 1330 and 1020 cm–1 were also found to increase during the same potential scan. The appearance of spectral changes above 3.3 V supports the model of two types of doping processes occurring in the polymer. The observed changes almost disappeared during the reverse scan. 相似文献
The photoelectric and photorefractive characteristics of polyvinylcarbazole (PVK) composites with 0.15 wt % graphene at a wavelength of 532 nm have been measured. The dependence of the quantum efficiency of generation of mobile charge carriers as determined from the photocurrent is well approximated by the Onsager equation calculated accurate to E03 for the quantum yield of thermalized electron-hole pairs of φ0 = 1 and their initial separation radius of r0 = 10.9 Å. The long-wavelength edge of optical absorption for PVK lies at 365 nm. Thus, the photogeneration of mobile carriers during illumination of the composite at 532 nm is due to photoexcitation of graphene. The measurement of the photorefractive properties has revealed that the two-beam coupling gain coefficient is Γ = 50 cm?1 at E0 = 150 V/μm and equal intensities of incident beams. It has been found that at E0 = 83.3 V/μm, the two-beam coupling gain coefficient increases from 8 to 14 cm?1 as the ratio of incident beam intensities I1(0)/I2(0) increases from 1 to 2.4. 相似文献
A method for quantitative depth profiling of polymer stabilisers in polypropylene materials is presented. Microtome cuts down to 10 μm thickness were prepared and an amount of as low as 10 mg was used for subsequent analysis. The sample preparation procedure included dissolution in toluene, followed by precipitation of the polymer by addition of methanol or acetonitrile, and subsequent analysis of the solution by reversed phase HPLC coupled with UV, MS and MS2 detection. A comparison of the different detection techniques is given and their particular advantages are discussed. Depending on the stabiliser type, the presented method with MS detection can quantify stabiliser concentrations down to 0.007 mg?L?1 (this corresponds to 0.0007 mg?g?1 in the polymer sample) with repeatabilities better than 5 % relative standard deviation (n?=?3). This equals a quantitation of absolute stabiliser amounts at the 0.1-μg level and concentrations down to 0.1 mg?L?1 in the corresponding polymer extracts. The developed method shows high sensitivity by the use of MS detection as well as good repeatabilities. Mainly due to the use of an appropriate internal standard, improved repeatability during sample extraction could be obtained. Furthermore, the applicability to real samples has been demonstrated. 相似文献
A pyrimethanil-imprinted polymer (P1) was prepared by iniferter-mediated photografting a mixture of methacrylic acid and ethylene dimethacrylate onto homemade near-monodispersed chloromethylated polydivinylbenzene beads. The chromatographic behaviour of a column packed with these imprinted beads was compared with another column packed with irregular particles obtained by grinding a bulk pyrimethanil-imprinted polymer (P2). The comparison was made using the kinetic model of non-linear chromatography, studying the elution of the template and of two related substances, cyprodinil and mepanipyrim. Extension of the region of linearity, capacity factors for the template and the related substances, column selectivity, binding site heterogeneity, apparent affinity constant (K) and lumped kinetic association (ka) and dissociation rate constant (kd) were studied during a large interval of solute concentration, ranging between 1 and 2000 μg/ml. From the experimental results obtained, in the linearity region of solute concentration column selectivity and binding site heterogeneity remained essentially the same for the two columns, while column capacity (at 20 μg/ml, P1 = 23.1, P2 = 11.5), K (at 20 μg/ml, P1 = 8.3 × 106 M−1, P2 = 2.5 × 106 M−1) and ka (at 20 μg/ml, P1 = 3.5 μM−1 s−1, P2 = 0.47 μM−1 s−1) significantly increased and kd (at 20 μg/ml, P1 = 0.42 s−1, P2 = 0.67 s−1) decreased for the column packed with the imprinted beads. These results are consistent with an influence of the polymerisation method on the morphology of the resulting polymer and not on the molecular recognition properties due to the molecular imprinting process. 相似文献
The research presented here evaluates the heat transfer coefficient of the contact interface of a thin liquid polymer film between a pair of columnar aluminum bodies with an initial temperature difference of approximately 160 K. We measured the unsteady temperature changes inside the columns. The heat transfer test was performed with three types of liquid polymers: squalane, oleic acid, and silicone oil. The heat transfer coefficient of the polymer films as a fitting parameter was obtained by ensuring the numerically computed time evolution of the columns’ temperature corresponded with the experimentally measured data. The interfacial heat transfer coefficients of the thin polymer films (mean thickness: 60 μm) for all three polymers used were 1.75 kW/m2·K, 2.75 kW/m2·K, and 4.10 kW/m2·K. The present estimating method for determining interfacial heat transfer coefficients was suitable for a material-polymer film-material contact model. The time evolution of the temperature at the contact surfaces was also effectively evaluated using the numerical simulation. 相似文献
Pulsed photoconductivity results are presented for single crystals of a fully-conjugated polymer, poly-2,4-hexadiyne-1,6-diol bis(p-toluene sulfonate). Carriers of both sign are observed and are found to have essentially identical action spectra with a photoconduction onset around 3 eV. Upper and lower limits could be placed on the charge carrier mobilities normal to the (011) crystallographic plain, which is roughly the polymer chain direction: 3 ? μe,h ? 10?3 cm2/V s. The mobilities normal to the chain are about a factor of 10 less. The carrier lifetimes are about 0.5 μs for both holes and electrons but strongly dependent on the method of polymerization of the precursor monomer crystals. 相似文献
A spectrophotometric determination of vanadium as vanadium(IV) pyridine thiocyanate is described. The blue complex is formed in acidic aqueous solution and extracted into pyridine-chloroform. Absorbance is measured at 7.40 mμ. The range of best accuracy for 1-cm cells is from about 80 to 240 μg of vanadium per ml, and sensitivity is 0.4 μg of vanadium per cm2 at 7.40 mμ. The vanadium may be present initially as vanadium(IV) or vanadium(V), which is reduced to vanadium(IV) by the large excess of thiocyanate ion added. Several elements interfere in the determination ; a separation procedure involving mercury cathode electrolysis is suggested. 相似文献
2-Naphthohydroxamic acid in methanol gives an intense and stable red-orange color with vanadium (V), sensitive to 0.009 μg V/cm2, for log I0/I = 0.001 abs. unit at wavelength 450 mμ. The value for σ is ±0.006 a.u., equivalent to ±0.08 p.p.m. V. The colored complex obeys Beer's law over the range 1–10 p.p.m. vanadium. The absorbance (in 1-cm cell) at 10 p.p.m. was so great that no data were obtained at higher concentrations. Under the conditions of the reaction, the combining ratio of vanadium and 2-naphthohydroxamic acid appears to be 1 to 2. Optimum conditions for the use of 2-naphthohydroxamic acid as a spectrophotometric reagent for vanadium-(V) were established; the procedure was applied to the determination of vanadium in steels and non-ferrous alloys with good precision and accuracy. 相似文献
Here, a conjugated polymer VTTPD based on thieno[3,4‐c]pyrrole‐4,6‐dione (TPD) and dithiophene with vinyl as linker is synthesized and characterized. Electrochemical and optical studies indicate the LUMO and HOMO energies of the polymer are −3.70 and −5.39 eV. Theoretical calculation with density functional theory suggests that H‐bonds are formed between the TPD carbonyl (O) and its neighboring vinyl (H) which benefit the planarity and π‐conjugation of the polymer backbone. Bottom contact bottom gate organic field effect transistor devices based on VTTPD are fabricated and examined in air. After annealing at 160 °C, the devices exhibit excellent performance of μh = 0.4 cm2 V−1 s−1, Ion/off = 106, Vth within −10 V to −5 V. Thin film morphologies before and after the annealing process are also investigated with XRD and AFM.
Voltammetric procedures for trace metals analysis in polluted natural waters using homemade bare gold-disk microelectrodes of 25- and 125-μm diameters have been determined. In filtered seawater samples, square wave anodic stripping voltammetry (SWASV) with a frequency of 25 Hz is applied for analysis, whereas in unfiltered contaminated river samples, differential pulse anodic stripping voltammetry (DPASV) gave more reliable results. The peak potentials of the determined trace metals are shifted to more positive values compared to mercury drop or mercury-coated electrodes, with Zn always displaying 2 peaks, and Pb and Cd inversing their positions. For a deposition step of 120 s at ?1.1 V, without stirring, the 25-μm gold-disk microelectrode has a linear response for Cd, Cu, Mn, Pb and Zn from 0.2 μg L?1 (1 μg L?1 for Mn) to 20 μg L?1 (30 μg L?1 for Zn, Pb and 80 μg L?1 for Mn). Under the same analytical conditions, the 125-μm gold-disk microelectrode shows linear behaviour for Cd, Cu, Pb and Zn from 1 μg L?1 (5 μg L?1 for Cd) to 100 μg L?1 (200 μg L?1 for Pb). The sensitivity of the 25-μm electrode varied for different analytes from 0.23 (±0.5%, Mn) to 4.83 (±0.9%, Pb) nA L μmol?1, and sensitivity of the 125-μm electrode varied from 1.48 (±0.7%, Zn) to 58.53 (±1.1%, Pb nA L μmol?1. These microelectrodes have been validated for natural sample analysis by use in an on-site system to monitor Cu, Pb and Zn labile concentrations in the Deûle River (France), polluted by industrial activities. First results obtained on sediment core issued from the same location have shown the ability of this type of microelectrode for in situ measurements of Pb and Mn concentrations in anoxic sediments. 相似文献