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1.
A chitosan/ionic liquid composite electrode was prepared and used to determine uric acid (UA) in the presence of a large excess of ascorbic acid (AA) and dopamine (DA) by linear sweep voltammetry (LSV). The modified electrode shows large peak separations between DA, AA, and UA. Due to the existence of chitosan and ionic liquid in the composite, the modified electrode exhibits strong electrochemical catalytic activity toward the oxidation of UA. Under optimal conditions, the peak current is linearly dependent on the UA concentration in the range of 5?×?10?7–2?×?10?4 M in the presence of 5?×?10?4 M AA and 5?×?10?5 M DA with a correlation coefficient of 0.9978, and the detection limit is 5?×?10?8 M at a signal-to-noise ratio of 3. With good sensitivity and stability, the constructed sensor was applied in the determination of UA in human serum samples and satisfactory results were obtained.  相似文献   

2.
Because of the surfaces of wood-plastic composite (WPC) materials are enriched in polymers of low surface energy, they exhibit low adhesion properties. UV/ozone is proposed as surface treatment for increasing the surface energy and adhesion of WPC materials made with different polymers (polyethylene, polypropylene and polyvinyl chloride). UV lamp-WPC surface distance and time of UV exposure were varied for optimizing UV/ozone treatment of WPC, and UV dose used ranged between 2.02 × 10?14 and 5.05 × 10?12 J·s/m2. UV/ozone treatment created new carbon-oxygen polar groups in WPC surfaces and increased their surface energy, mainly their polar component. Furthermore, ablation of the outermost WPC surface was produced, more noticeably by reducing the distance between WPC surface and UV lamp and by increasing the duration of the treatment. Noticeable increase in 180° peel adhesion was obtained in the joints made with UV/ozone treated WPC at 10–30 mm distance during 1–5 min (i.e., UV dose between 5.61 × 10?14 and 2.53 × 10?12 J·s/m2). Although 180° peel strength of joints made with acrylic adhesive tape and UV/ozone treated WPC for 10 min and 10 mm distance (UV dose: 5.05 × 10?12 J·s/m2) was not increased because of dominant effect of ablation over creation of polar groups, the cross-hatch adhesion to different coatings was highly improved, irrespective of the polymer used and the wood content of WPC; however, the surface modifications and adhesion of UV/ozone treated WPC were more marked when its wood content was higher and by using UV dose between 0.10 × 10?12 and 2.53 × 10?12 J·s/m2.  相似文献   

3.
Organic/inorganic composite membranes were prepared using sulfonated poly(vinyl alcohol) (SPVA), mixed and cross-linked with different amounts of poly(vinyl alcohol)-grafted graphene oxide (PVA-g-GO). The introduction of PVA-g-GO to the membranes not only reduced the methanol permeability but also positively affected the mechanical properties: Increasing the PVA-g-GO content increased the blocking effect of GO. The PVA-g-GO/SPVA membranes were cross-linked with glutaraldehyde, resulting in the formation of cross-linking chains within the matrix, as well as between the matrix and the filler. Therefore, the microstructure of the PVA-g-GO/SPVA cross-linking membrane was different from that of the existing membranes. This structure also reduced the methanol permeability. The composite membranes exhibited proton conductivities ranging from 0.0141 to 0.0319 S/cm at 60 °C, and low methanol permeability ranging from 3.13?×?10?7 to 1.53?×?10?7 cm2 s?1 at 25 °C.  相似文献   

4.
A report on the fabrication and characterization of high performance conventional and ring-shaped AlGaN/GaN Schottky barrier diode on Si is presented. The resulting device exhibited low leakage current, which led to a detectivity performance of 3.48×1013 and 1.76×1013 cm?Hz1/2 W?1, respectively, for both conventional and ring-shaped Schottky diode. The differential resistances of both devices were obtained at approximately 1.37×1012 and 1.41×1013 Ω, respectively. The zero bias peak responsivities of conventional and ring-shaped Schottky diodes were estimated to be 3.18 and 2.08 A?cm?2/W, respectively. The typical UV to visible rejection ratio was observed over three orders of magnitude at zero bias. The CV measurements was used to calculate and analyze the polarization sheet charge density of the AlGaN barrier layer by using self-consistently solving Schrodinger’s and Poisson’s equations. It is demonstrated that the ring shape of the Schottky barrier has higher polarization sheet charge density, which has the consequence that the Schottky shape has influence on the strain of the AlGaN barrier layer.  相似文献   

5.
A novel biosensor has been constructed by incorporating modified nanosized natural zeolite and 3-hydroxypropanaminium acetate (HPAA) as a novel room temperature ionic liquid, supported on multiwalled carbon nanotube (MWCNTs) and employed for the simultaneous determination of dopamine (DA) and uric acid (UA). A detailed investigation by transmission electron microscopy and electrochemistry is performed in order to elucidate the preparation process and properties of the composites. The voltammetric studies using the modified carbon paste electrode show two well-resolved anodic peaks for DA and UA with a potential difference of 160 mV, revealing the possibility of the simultaneous electrochemical detection of these compounds. The modified carbon paste electrode shows good conductivity, stability, and extraction effect due to the synergic action of HPAA, MWCNTs, and iron ion-doped natrolite zeolite. Under optimized conditions, the peak currents are linear from 8.12?×?10?7 to 3.01?×?10?4?mol?L?1 and from 9.31?×?10?7 to 3.36?×?10?4?mol?L?1 with detection limits of 1.16?×?10?7 and 1.33?×?10?7?mol?L?1 for DA and UA using the differential pulse voltammetric method, respectively. Finally, the modified carbon paste electrode proved to have good sensitivity and stability and is successfully applied for the simultaneous determination of DA and UA in human blood serum and urine samples.  相似文献   

6.
Solid polymer electrolytes based on potato starch (PS) and graphene oxide (GO) have been developed in this study. Blending GO with PS has improved the ionic conductivity and mechanical properties of the electrolytes. In this work, series of polymer blend consisting of PS and GO as co-host polymer were prepared using solution cast method. The most amorphous PS-GO blend was obtained using 80 wt% of PS and 20 wt% of GO as recorded by X-ray diffraction (XRD). Incorporation of 40 wt% lithium trifluoromethanesulfonate (LiCF3SO3) into the PS-GO blend increases the conductivity to (1.48 ± 0.35) × 10?5 S cm?1. Further enhancement of conductivity was made using 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]). The highest conductivity at room temperature is obtained for the electrolyte containing 30 wt% of [Bmim][Cl] with conductivity value of (4.8?0 ± 0.69) × 10?4 S cm?1. Analysis of the Fourier transform infrared spectroscopy (FTIR) spectra confirmed the interaction between LiCF3SO3, [Bmim][Cl], and PS-GO blend. The variation of the dielectric constant and modulus studies versus frequency indicates that system of PS-GO-LiCF3SO3-[Bmim][Cl] obeys non-Debye behavior.  相似文献   

7.
Thermal effects on ultra-high-molecular-weight polyethylene (UHMWPE) residual radicals during the vitamin E diffusion process were studied in detail. Electron paramagnetic resonance (EPR) technique showed a significant reduction in concentrations of radiation-induced primary (alkyl (–CH2?CH–CH2–), allyl (–CH2?CH=CH–CH–CH2–) and polyenyl (–?CH–[CH=CH–] m –) with m > 3) radicals for both control and vitamin E-doped samples. The concentrations of radiation-induced primary radicals (RIPRs) were found to decrease proportionally with the heat/diffusion time. While the EPR spectra of the control samples showed only polyethylene (PE) radicals, the spectra of vitamin E-doped samples were found to exhibit vitamin E radicals in addition to PE radicals. Of particular interest, the heat involved during vitamin E diffusion plays a significant role in reducing the radiation-induced primary radicals of UHMWPE. For 120 min of heat/diffusion time, the available quantity of primary radicals in control samples were found to be ~7.5 % of initial radicals. The leftover amounts of these primary radicals for vitamin E-doped samples were approximately ~10.0 %. In addition to this, EPR power saturation techniques were also used to assess the effects of initial heat/diffusion treatment on the oxygen-induced residual radicals (OIRRs): R1 (–?CH–[CH=CH–] m –) with m > 3 and R2 (?OCH–[CH=CH–] m –) with m = 2 or 3. It was found that the concentration of OIRRs also decreases proportionally with initial heat/diffusion time. The remaining amount of OIRRs relative to leftover RIPRs after heat/diffusion was found to be approximately 4.0 % in controls and was still found to be 10.0 % in vitamin E-doped UHMWPE. This may indicate that vitamin E slows down the oxidation processes, which may contribute to the strong oxidation resistance of vitamin E-doped UHMWPE.  相似文献   

8.
In the article, graphene oxide (GO) was prepared by flake graphite, nitric acid and peroxyacetic acid via the sonochemical method and characterized, and polyvinyl alcohol carbonate/GO composite (PVAC/GO composite) was synthesized by polyvinyl alcohol (PVA), dimethyl carbonate (DMC) and GO via the approach of transesterification in the case of ultrasonic-microwave synergistic effects and characterized, and three-dimensional PVAC/GO sponge (3D PVAC/GO sponge) was manufactured by PVAC/GO composite via the foaming approach and characterized, and the thermal stability and surface resistivity of 3D PVAC/GO sponge were investigated. Based on those, it had been attested that PVAC polymer was structured by DMC and PVA and had the six-membered lactone rings and the ether bonds, and PVAC/GO composite was constituted by 2D GO lattice and PVAC polymer, and 3D PVAC/GO sponge was constructed by PVAC/GO composite, and the surface resistivity of 3D PVAC/GO sponge with 0.00, 0.60, 1.20, 1.80 and 2.40 g of GO were 9.07 × 107, 6.02 × 107, 4.65 × 107, 2.47 × 107 and 1.06 × 107 O/sq, and the thermal stability of 3D PVAC/GO sponge had improved.  相似文献   

9.
The polyvinylidene difluoride-co-hexafluoropropylene (PVdF-HFP) nanocomposite solid polymer electrolyte films were developed by solution-casting method. PVdF-HFP as a polymer host, lithium perchlorate (LiClO4) as a salt for lithium ion, and ZnO nanoparticles as fillers were used to form the nanocomposite solid polymer electrolyte films. All the prepared samples were characterized by X-ray diffraction (XRD), differential scanning calorimetry, and scanning electron microscopy. The XRD patterns of the pure and nanocomposite solid polymer electrolyte samples indicate the formation of amorphous phase with 17.5 wt.% of lithium salt and ZnO fillers up to 3 wt.%. The total conductivity and lithium ion transference number were studied at room temperature by using impedance spectroscopy and Wagner’s polarization methods. The highest conductivity at room temperature for solid polymer electrolyte and nanocomposite solid polymer electrolyte are found to be 3.208?×?10?4 and 1.043?×?10?3 S/cm, respectively. Similarly, the lithium ion transference number is evaluated for the optimized solid polymer electrolyte and nanocomposite solid polymer electrolyte films with 3 wt.% of ZnO fillers. And it is found that ionic transference number could be enhanced from 92 to 95 % with the addition of nanosized ZnO fillers to the solid polymer electrolyte.  相似文献   

10.
In the present work, adhesion, leak rate, and chemical compatibility of a series of borosilicate-based glasses, belonging to the ternary BaO–SiO2–B2O3 system, with AISI 430 alloys as interconnect were investigated for solid oxide fuel cell applications. Wetting angle and deformation behavior of the selected glasses with temperature and time were initially characterized with the hot-stage microscope. It was observed that the temperature ranges of wetting for all combinations were greater than 1000 °C. Significant deformation did not appear in the samples over soaking time at sealing temperature. In the next step, the leakage tests of AISI430/glass-ceramic couples were performed. The sample containing 32 % molar BaO (Ba32) had no gas leakage; a low leak rate of 10?7to 10?8 Pam3 s?1 was obtained for the glass with 37 % molar BaO (Ba37) and big leak of the system (10?3to 10?4 Pam3 s?1) for Ba42. Possible interfacial reactions between the as-received glass and cell ingredients and aging up to 100 h were studied by scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy and X-ray dot mapping. The results showed that the Ba32 and Ba37 glasses coupled with AISI had fine adhesion, which remained stable under these conditions and were compatible with the interconnect. So, the use of these glass-ceramics will probably be successful in joining the ceramic electrolytes to the metallic interconnect.  相似文献   

11.
In this study, poly (vinyl chloride)(PVC) membrane electrodes with/without multi-walled carbon nanotubes (MWCNTs) based on a calix[4]arene derivative for perchlorate ion were described. The influence of membrane composition, pH, conditioning solution on the potentiometric response of the electrodes was investigated. Perchlorate-selective PVC membrane electrode exhibited a slope of 47.8 ± 0.6 mV/pClO4 in the range of 1.0 × 10?7–1.0 × 10?1 mol L?1at pH 4.0 while the coated Pt electrodes with MWCNT-OH, MWCNT-COOH and MWCNT displayed slopes of 46.1 ± 0.7 mV/pClO4 (5.0 × 10?6–1.0 × 10?1 mol L?1), 50.4 ± 1.9 mV/pClO4 (1.0 × 10?6–1.0 × 10?1 mol L?1) and 44.4 ± 0.3 mV/pClO4 (1.0 × 10?5–1.0 × 10?1 mol L?1), respectively. Other response characteristics of these electrodes such as response time, lifetime and detection limit were identified, and the selectivity coefficients towards various anions were calculated by separate solution method. Moreover, the perchlorate-selective electrodes described here were successfully used as an indicator electrode for the determination of perchlorate in real samples such as tap water, river water and human urine by direct calibration method.  相似文献   

12.
Suwen Wang  Lei Jin  Zhongfang Li 《Ionics》2013,19(7):1027-1036
Polymer composite membranes based on sulfonated poly(phthalazinone ether sulfone) (SPPES) and zirconium sulfophenyl phosphate (ZrSPP) were prepared. Three ZrSPP concentrations were used: 10, 20, and 30 wt%. The membranes were characterized by infrared spectroscopy (IR), X-ray diffraction spectroscopy, thermal gravimetric analysis, and scanning electron microscopy (SEM). The IR results indicated the formation of intense hydrogen bonds between ZrSPP and SPPES molecules. The SEM micrographs showed that ZrSPP well dispersed with SPPES and form a lattice structure. The proton conductivity of the SPPES (degree of sulfonation (DS) 64 %)/ZrSPP (10 wt%) composite membrane reached 0.39 S/cm at 120 °C 100 % relative humidity and that of the 30 wt% of SPPES (DS 16.1 %)/ZrSPP composite membrane reached 0.18 S/cm at 150 °C. The methanol permeabilities of the SPPES/ZrSPP composite membranes were in the range of 2.1?×?10?8 to 0.13?×?10?8?cm2/s, much lower than that of Nafion®117 (10?6?cm2/s). The composite membranes exhibited good thermal stabilities, proton conductivities, and good methanol resistance properties.  相似文献   

13.
The silver ions and l-phenylalanine were co-deposited and formed a hybrid membrane on the surface of glassy carbon electrode by cyclic voltammetry. The membrane had good properties for catalyzing the redox of catecholamine neurotransmitters, including epinephrine (EP), norepinephrine (NE), and dopamine (DA). The electrochemical behaviors of these neurotransmitters were studied on this modified electrode. and therefore, an assay for each of them is set up and the detection limits for EP, NE, and DA are 7.2?×?10?9, 6.4?×?10?9, and 8.5?×?10?9 mol L?1, respectively. The proposed method can effectively eliminate the interference of the ascorbic acid and uric acid. The conditions which influenced the analyses were optimized. Using this method to determine the content of EP, NE, and DA in injections, the results were satisfactory.  相似文献   

14.
Vanadium dioxide thin films have been deposited on Corning glass substrates by a KrF laser ablation of V2O5 target at the laser fluence of 2 J?cm?2. The substrate temperature and the target-substrate distance were set to 500 °C and 4 cm, respectively. X-ray diffraction analysis showed that pure VO2 is only obtained at an oxygen pressure range of 4×10?3–2×10?2 mbar. A higher optical switching contrast was obtained for the VO2 films deposited at 4×10?3–10?2 mbar. The films properties were correlated to the plume-oxygen gas interaction monitored by fast imaging of the plume.  相似文献   

15.
The use of a biocompatible and thermoresponsive polymer, poly(2-hydroxyethyl methacrylate) (PHEMA) grafted onto the surface of graphene oxide (GO) as an adsorbent for the removal of a cationic dye (methylene blue [MB]) from an aqueous solution is examined in this work. GO–PHEMA forms a hydrogel in water thus overcoming the problem faced by carbon-based adsorbent materials during post-treatment (i.e., separation of adsorbent from the aqueous phase). The GO–PHEMA composite was synthesized using a green approach through dispersion polymerization in supercritical CO2. The successful preparation of this composite was confirmed by a series of characterization techniques. The adsorption behavior of the composite toward MB such as the effect of the adsorbent dosage, pH, contact time, dye concentration, and recyclability were observed. In addition, the adsorption isotherm, kinetics and thermodynamics were investigated. According to the experimental data, the adsorption parameters were found to fit well into the Freundlich adsorption isotherm with a correlation coefficient of 0.975 and a maximum predicted adsorption capacity of 39.41 mg g?1 at 25 °C. The adsorption kinetics studies showed that the adsorption behavior followed a pseudo-second-order reaction. On the other hand, the thermodynamics studies showed that the adsorption of MB on GO–PHEMA composite followed spontaneous and endothermic adsorption process with an efficient adsorption temperature at 45 °C. The experimental results also showed that the GO–PHEMA composite could remove 99.8% of the dye in 45 min. Therefore, GO–PHEMA composite is a favorable green adsorbent for environmental applications.  相似文献   

16.
Abstract

The effects of three systems on the chemiluminescence (CL) intensity have been studied in this paper, such as leucogen–potassium permanganate–rhodamine B, leucogen–cerium (IV)–rhodamine B, and leucogen–luminol–hydrogen peroxide (called system 1, system 2, and system 3, respectively). The mechanism of these reactions is also discussed. Surfactant (CTMAB) has a remarkably sensitive effect on these systems mentioned above. Therefore, three new flow injection chemiluminescence methods for the determination of leucogen have been established. For system 1, the linear range is 8.0×10?8 to 4.0×10?5 g mL?1, with limits of detection 2×10?8 g mL?1; the relative standard deviation is 2.5% (n=11, Cs=4.0×10?6 g mL?1). For system 2, the linear range is 1.0×10?8 to 5.0×10?6 g mL?1, with limits of detection 3×10?9 g mL?1; the relative standard deviation is 5.1% (n=11, Cs=1.0×10?6 g mL?1). For system 3, the linear range is 4.0×10?8 to 2.0×10?6 g mL?1, with limits of detection 1×10?8 g mL?1; the relative standard deviation is 1.3% (n=11, Cs=1.0×10?7 g mL?1). Compared with the three methods above, system 3 is confirmed as the best method. This method has been applied to the determination of leucogen with satisfactory results.  相似文献   

17.
An efficient approach was employed to simultaneously functionalize and reduce the graphene oxide (GO) with p-phenylene diamine (PPD) using simple refluxing. There was a possibility of nucleophilic substitution of amino moieties of PPD with the epoxy groups of GO. The polythiophene (PTh) and polythiophene-co-poly(methylmethacrylate) (PTh-co-PMMA) nanocomposites with chemically modified GO were prepared using in situ polymerization technique. Two series of nanocomposites that is PTh/PPD-GO and PTh-co-PMMA/PPD-GO were designed. The nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, scanning electron microscopy (SEM), thermal conductivity, and electrical conductivity measurement. The FTIR spectra depicted the characteristic absorption peaks for the formation of copolymer and their composites with PPD-GO. The SEM micrographs showed that the PPD-GO nanosheets were homogeneously dispersed in copolymer matrix forming nano-granular morphology. The nanofluids were prepared by suspending modified GO particles inside the basefluid of polythiophene and PTh-co-PMMA. The thermal conductivity of nanocomposites was significantly improved even with low PPD-GO loading. The thermal conductivity of PTh-co-PMMA/PPD-GO with 1.5 wt.% filler was increased to 1.42 W/mK at a higher temperature. The XRD patterns confirmed the presence of chemical interactions between the copolymer and filler particles. The electrical conductivity of PTh-co-PMMA/PPD-GO was also found to increase in the range of 6.1 × 10?3–2.5 × 10?2 S/cm. Novel PTh-co-PMMA/PPD-GO-based nanocomposite is potentially significant in high-performance thermal systems.  相似文献   

18.
High-density polyethylene (HDPE) composites reinforced with multiwalled carbon nanotubes (MWCNTs) and nano-silicon dioxide (SiO2) fillers were evaluated for flame retardancy and thermal properties for cable and wire applications. In this study, the filler percentages of MWCNT and nano-SiO2 have varied from 0 to 5 wt% in HDPE composite with polyethylene-grafted glycidyl methacrylate compatibilizer and 3-aminopropyl triethoxy silane coupling agent. Addition of MWCNT’s and nano-SiO2 to the HDPE composite is observed to enhance the limiting oxygen index and char formation. Cone calorimeter results also show a 53% reduction in the peak heat release rate of the HDPE composite with 5 wt% of MWCNT. The existence of synergism between the uniformly dispersed MWCNT and nano-SiO2 has been verified using Finite Element Method (FEM)-based thermal simulations.  相似文献   

19.
Glassy LiPO3/crystalline Al2O3 and glassy LiPO3/crystalline ZrO2 (0–12.5 vol.% of oxide fillers) composite solid electrolytes have been prepared by glass matrix softening. Their thermal and transport properties have been investigated by differential scanning calorimetry (DSC) and impedance spectroscopy methods. The addition of ZrO2 leads to a decrease in the crystallization temperature of LiPO3 glass. It was found that the conductivity behavior depends on the nature of the dispersed addition. In the case of the Al2O3 addition, the increase in the electrical conductivity is observed. The ionic conductivity of the LiPO3/10% Al2O3 composite reaches 5.8 × 10?8 S/cm at room temperature. In contrast, the conductivity in the LiPO3/ZrO2 composite system decreases.  相似文献   

20.
In this work, we investigate the electrical, structural, and thermal properties of composite polymer electrolytes (CPEs). Different mass fractions of antimony trioxide filler, Sb2O3, are added into poly(acrylic acid) (PAA)-based polymer electrolytes with N-lithiotrifluoromethane sulphonamide [LiN(SO2CF3)2] (LiTFSI) as doping salt. Characteristics such as alternating current (AC)–impedance spectroscopy, attenuated total reflectance–Fourier transform infrared (ATR-FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) are analyzed. The highest ionic conductivity of (2.15?±?0.01)?×?10?4 S cm?1 is achieved at room temperature with addition of 6 wt% of fillers. The ionic transportation is further proven in a transference number study under DC polarization, whereas ATR-FTIR is employed to explore the complexation between PAA, LiTFSI, and Sb2O3. TGA reveals the improved thermal stability of CPEs. The glass transition temperature (T g) is reduced upon addition of Sb2O3 as shown in DSC analysis.  相似文献   

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