共查询到20条相似文献,搜索用时 46 毫秒
1.
Najoua Katif Rachel A. Harries Andrew M. Kelly John S. Fossey Tony D. James Frank Marken 《Journal of Solid State Electrochemistry》2009,13(10):1475-1482
The transfer of the α-hydroxy-carboxylates of glycolic, lactic, mandelic and gluconic acid from the aqueous electrolyte phase
into an organic 4-(3-phenylpropyl)-pyridine (PPP) phase is studied at a triple-phase boundary electrode system. The tetraphenylporphyrinato
complex MnTPP dissolved in PPP is employed to drive the anion transfer reaction and naphthalene-2-boronic acid (NBA) is employed
as a facilitator. In the absence of a facilitator, the ability of α-hydroxy-carboxylates to transfer into the organic phase
improves, consistent with hydrophobicity considerations giving relative transfer potentials (for aqueous 0.1 M solution) of
gluconate>glycolate>lactate>mandelate. In the presence of NBA, a shift of the reversible transfer potential to more negative
values is indicating fast reversible binding (the mechanism for the electrode process is EICrev) and the binding constants are determined as K
glycolate = 2 M−1, K
mandelate = 60 M−1, K
lactate = 130 M−1 and K
gluconate = 2,000 M−1. The surprisingly strong interaction for gluconate is rationalised based on secondary interactions between the gluconate
anion and NBA. 相似文献
2.
Luis A. Toledo-Matos Maximo Antonio Pech-Canul 《Journal of Solid State Electrochemistry》2011,15(9):1927-1934
The evolution under open-circuit conditions of iron passive films formed at 0.8 VSCE in a borate buffer solution at pH 8.4 was investigated with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry.
The composition of the freshly formed passive film as determined by X-ray photoelectron spectroscopy (XPS) was found to be
in agreement with a bilayer model, where the inner layer is composed mainly of iron oxide and the outer layer consists of
a hydrated material. Results of XPS measurements also showed that the open-circuit breakdown of passive films was consistent
with a reductive dissolution mechanism. When the iron electrode reached an intermediate stage in the open-circuit potential
decay (approximately −0.3 VSCE), the oxide film, containing both Fe(II) and Fe(III), was still protective. The impedance response in this stage exhibited
a mixed control by charge transfer at the metal/film and film/solution interfaces and diffusion of point defects through the
film. At the final stage of the open-circuit potential decay (approximately −0.7 VSCE), the oxide film was very thin, and the ratio of Fe3+/Fe2+ and O2−/OH− had decreased significantly. The impedance response also exhibited a mixed charge-transfer–diffusion control, but the diffusion
process was related to transport of species in the electrolyte solution resulting from dissolution of the oxide film. 相似文献
3.
Functionalized polypyrrole films were prepared by incorporation of Fe(CN)6
3− as doping anion during the electropolymerization of pyrrole at a glassy carbon electrode from aqueous solution. The electrochemical
behavior of the Fe(CN)6
3−/Fe(CN)6
4− redox couple in polypyrrole was studied by cyclic voltammetry. An obvious surface redox reaction was observed and dependence
of this reaction on the solution pH was illustrated. The electrocatalytic ability of polypyrrole film with ferrocyanide incorporated
was demonstrated by oxidation of ascorbic acid at the optimized pH of 4 in a glycine buffer. The catalytic effect for mediated
oxidation of ascorbic acid was 300 mV and the bimolecular rate constant determined for surface coverage of 4.5 × 10−8 M cm−2 using rotating disk electrode voltammetry was 86 M−1 s−1. Furthermore, the catalytic oxidation current was linearly dependent on ascorbic acid concentration in the range 5 × 10−4–1.6 × 10−2 M with a correlation coefficient of 0.996. The plot of i
p versus v
1/2 confirms the diffusion nature of the peak current i
p.
Received: 12 April 1999 / Accepted: 25 May 1999 相似文献
4.
Salimi Abollah Noorbakhsh Abdollah Semnani Abolfazl 《Journal of Solid State Electrochemistry》2011,15(9):2041-2052
A simple method was used to fabricate flavin adenine dinucleotide (FAD)/NiOx nanocomposite on the surface of glassy carbon
(GC) electrode. Cyclic voltammetry technique was applied for deposition nickel oxide nanostructures onto GC surface. Owing
to its high biocompatibility and large surface area of nickel oxide nanomaterials with immersing the GC/NiOx-modified electrode
into FAD solution for a short period of time, 10–140 s, a stable thin layer of the FAD molecules immobilized onto electrode
surface. The FAD/NiOx films exhibited a pair of well-defined, stable, and nearly reversible CV peaks at wide pH range (2–10).
The formal potential of adsorbed FAD onto nickel oxide nanoparticles film, E
o′ vs. Ag/AgCl reference electrode is −0.44 V in pH 7 buffer solutions was similar to dissolved FAD and changed linearly with
a slope of 58.6 mV/pH in the pH range 2–10. The surface coverage and heterogeneous electron transfer rate constant (k
s
) of FAD immobilized on NiOx film glassy carbon electrode are 4.66 × 10−11 mol cm−2 and 63 ± 0.1 s−1, indicating the high loading ability of the nickel oxide nanoparticles and great facilitation of the electron transfer between
FAD and nickel oxide nanoparticles. FAD/NiOx nanocomposite-modified GC electrode shows excellent electrocatalytic activity
toward S2O82− reduction at reduced overpotential. Furthermore, rotated modified electrode illustrates good analytical performance for amperometric
detection of S2O82−. Under optimized condition, the concentration calibration range, detection limit, and sensitivity were 3 μM–1.5 mM, 0.38 μM
and 16.6 nA/μM, respectively. 相似文献
5.
An anodic stripping voltammetric procedure for the determination of Cu(II) at an in situ-plated stannum film electrode (SnFE)
was described. The results indicated that the SnFE had an attractive electroanalytical performance, with two distinct voltammetric
stripping signals for copper and stannum, and showed the superior advantage for the determination of copper compared with
the bismuth film electrode. Several experimental parameters were optimized. The SnFE exhibited highly linear behavior in the
concentration range from 1.0 to 100.0 μg L−1 of Cu(II) (r = 0.994) with the detection limit of 0.61 μg L−1 (S/N = 3), and the relative standard deviation for a solution containing 40.0 μg L−1 Cu(II) was 2.2% (n = 8). The procedure has been successfully applied for the determination of Cu(II) in lake water sample. 相似文献
6.
Sayed Medhi Ghoreishi Mohsen Behpour Mohammad Hassan Motaghedi Fard 《Journal of Solid State Electrochemistry》2012,16(1):179-189
In this work, we investigate the electrochemical activity of dopamine (DA) and uric acid (UA) using both a bare and a modified
carbon paste electrode as the working electrode, with a platinum wire as the counter electrode and a silver/silver chloride
(Ag/AgCl) as the reference electrode. The modified carbon paste electrode consists of multi-walled carbon nanotubes (>95%)
treated with α-cyclodextrine, resulting in an electrode that exhibits a significant catalytic effect toward the electro-chemical
oxidation of DA in a 0.2-M Britton–Robinson buffer solution (pH 5.0). The peak current increases linearly with the DA concentration
within the molar concentration ranges of 2.0 × 10−6 to 5.0 × 10−5 M and 5.0 × 10−5 to 1.9 × 10−4 M. The detection limit (signal to noise >3) for DA was found to be 1.34 × 10−7 M, respectively. In this work, voltammetric methods such as cyclic voltammetry, chronoamperometry, chronocuolometry, differential
pulse and square wave voltammetry, and linear sweep and hydrodynamic voltammetry were used. Cyclic voltammetry was used to
investigate the redox properties of the modified electrode at various scan rates. The diffusion coefficient (D, cm2 s−1 = 3.05 × 10−5) and the kinetic parameters such as the electron transfer coefficient (α = 0.51) and the rate constant (k, cm3 mol−1 s−1 = 1.8 × 103) for DA were determined using electrochemical approaches. By using differential pulse voltammetry for simultaneous measurements,
we obtained two peaks for DA and UA in the same solution, with the peak separation approximately 136 mV. The average recovery
was measured at 102.45% for DA injection. 相似文献
7.
Dhanaji S. Dalavi Meenatai J. Suryavanshi Sawanta S. Mali Dipali S. Patil Pramod S. Patil 《Journal of Solid State Electrochemistry》2012,16(1):253-263
In this paper, we report on the nickel oxide (NiO) thin films potentiostatically electrodeposited onto indium-doped tin oxide-coated
glass substrates by using two types of organic surfactants: (1) non-ionic: polyethylene glycol (PEG), polyvinylpyrrolidone
(PVP) and (2) anionic: sodium dodecyl sulfate (SDS). An aqueous solution containing nickel sulfate precursor and potassium
hydroxide buffer was used to grow the samples. The effect of organic surfactants on its structural, morphological, wettability,
optical, electrochromic, and in situ colorimetry were studied using X-ray diffraction, scanning electron microscopy, contact
angle, FT-IR spectroscopy, optical transmittance, cyclic voltammetry, and CIE system of colorimetry. X-ray diffraction patterns
show that the films are polycrystalline, consisting of NiO cubic phase. A nanoporous structure with pore diameter of about
150–200 nm was observed for pure NiO. The films deposited with the aid of organic surfactants exhibits various surface morphological
feature. PVP-mediated NiO thin film shows noodle-like morphology with well-defined surface area whereas, an ordered pore structure
composed of channels of uniform diameter of about 60–80 nm was observed for PEG. A compact and smooth surface with nanoporous
structure stem from SDS helps for improved electrochromic performance compared with that of NiO deposits from surfactant-free
solution. Wetting behavior shows, transformation from hydrophilic to superhydrophilic nature of NiO thin films deposited with
organic surfactant, which helps for much more paths for electrolyte access. The surfactant-mediated NiO produce high color/bleach
transmittance difference up to 57% at 630 nm. On oxidation of NiO/SDS, the CIELAB 1931 2° color space coordinates show the
transition from colorless to the deep brown state (L* = 84.41, a* = −0.33, b* = 4.41, and L* = 43.78, a* = 7.15, b* = 13.69), with steady decrease in relative luminance. The highest coloration efficiency of 54 cm2 C−1 with an excellent reversibility of 97% was observed for NiO/SDS thin films. 相似文献
8.
Poly(vinylferrocenium) perchlorate–polyaniline (PVF+–PANI) composite film was synthesized electrochemically on Pt electrode in a methylene chloride solution containing a mixture
of poly(vinylferrocene) (PVF) polymer and aniline monomer. PVF+ polymer in the composite film was used as an electron transfer mediator. The composite coating showed significant electrochemical
activity towards hydroquinone (HQ) at pH 4, with high sensitivity and a wide linearity range. The interaction of HQ with PVF+ and PANI homopolymer films was investigated electrochemically and spectroscopically. HQ molecules are accumulated on the
electrode surface due to trapping by both polymers in the composite film and then oxidized catalytically by PANI. The most
significant contribution of PVF+ polymer is that it facilitates electron transfer in the composite film. The linear response range was found to be between
1.60 × 10−4 mM and 115 mM (R
2 = 0.999) at 0.45 V vs saturated calomel electrode. The limit of detection (LOD) was 4.94 × 10−5 mM. 相似文献
9.
Shuhu Xiao Jiuhui Qu Huijuan Liu Xu Zhao Dongjin Wan 《Journal of Solid State Electrochemistry》2009,13(12):1959-1964
Titanium oxide nanotube electrodes were successfully prepared by anodic oxidation on pure Ti sheets in 0.5 wt.% NH4F + 1 wt.% (NH4)2SO4 + 90 wt.% glycerol mixed solutions. Nanotubes with diameter 40–60 nm and length 7.4 μm were observed by field emission scanning
electron microscope. The electrochemical and photoelectrochemical characteristics of TiO2 nanotube electrode were investigated using linear polarization and electrochemical impedance spectroscopy techniques. The
open-circuit potential dropped markedly under irradiation and with the increase of Cl− concentrations. A saturated photocurrent of approximately 1.3 mA cm−2 was observed under 10-W low-mercury lamp irradiation in 0.1 M NaCl solution, which was much higher than film electrode. Meanwhile,
the highest photocurrent in NaCl solution implied that the photogenerated holes preferred to combine with Cl−. Thus, a significant synergetic effect on active chlorine production was observed in photoelectrocatalytic processes. Furthermore,
the generation efficiency for active chlorine was about two times that using TiO2/Ti film electrode by sol–gel method. Finally, the effects of initial pH and Cl− concentration were also discussed. 相似文献
10.
Ai-Lin Liu Jia-Dong Wang Wei Chen Xing-Hua Xia Yuan-Zhong Chen Xin-Hua Lin 《Journal of Solid State Electrochemistry》2012,16(4):1343-1351
A simple, rapid, sensitive, and accurate method for simultaneous electrochemical determination of procaine and its metabolite
(p-aminobenzoic acid, PABA) for pharmaceutical quality control and pharmacokinetic research was developed using a graphite paste
electrode. The differential pulse voltammetric results revealed that procaine and p-aminobenzoic acid, respectively, showed well-defined anodic oxidation peaks on a carbon paste electrode with a current peak
separation of 155 mV at a scan rate of 100 mV s−1. This well separation of the current peaks for these two compounds in voltammetry enables us to simultaneously determine
them. Good linearity (r > 0.998) between oxidation peak current and concentration was obtained in the range of 5.0 × 10−7–5.0 × 10−5 M for procaine and 5.0 × 10−7–2.0 × 10−5 M for PABA in pH 4.50 acetate buffer solution. The detection limit for both analytes is 5 × 10−8 M (S/N = 3:1). The present voltammetric method has been successfully used to determine trace p-aminobenzoic acid in procaine hydrochloride injection and procaine in plasma with a linear relationship of current to its
concentration ranging from 1.0 × 10−6 to 5.0 × 10−5 M (correlation coefficient of 0.9981) with a low detection limit of 5.0 × 10−7 M (S/N = 3:1). This validated method is promising to the study of pharmacokinetics in Sprague–Dawley rat and rabbit plasma after
an intravenous administration of procaine hydrochloride injection. 相似文献
11.
Xiaomei Cao Yanhong Xu Liqiang Luo Yaping Ding Ying Zhang 《Journal of Solid State Electrochemistry》2010,14(5):829-834
A glassy carbon electrode (GCE) modified with the film composed of chitosan incorporating cetylpyridine bromide is constructed
and used to determine uric acid (UA) and ascorbic acid (AA) by differential pulse voltammetry (DPV). This modified electrode
shows efficient electrocatalytic activity and fairly selective separation for oxidation of AA and UA in mixture solution.
UA is catalyzed by this modified electrode in phosphate buffer solution (pH 4.0) with a decrease of 80 mV, while AA is catalyzed
with a decrease of 200 mV in overpotential compared to GCE, and the peak separation of oxidation between AA and UA is 260
mV, which is large enough to allow the determination of one in presence of the other. Under the optimum conditions, the anodic
peak currents (I
pa) of DPV are proportional to the concentration of UA in the range of 2.0 × 10−6 to 6.0 × 10−4 M, with the detection limit of 5.0 × 10−7 M at a signal-to-noise ratio of 3 (S/N = 3) and to that of AA in the range of 4.0 × 10−6 to 1.0 × 10−3 M, with the detection limit of 8.0 × 10−7 M (S/N = 3). 相似文献
12.
A new H2O2 biosensor was fabricated on the basis of nanocomposite films of hemoglobin (Hb), silver nanoparticles (AgNPs), and multiwalled
carbon nanotubes (MWNTs)–chitosan (Chit) dispersed solution immobilized on glassy carbon electrode (GCE). The immobilized
Hb displayed a pair of well-defined and reversible redox peaks with a formal potential (E
θ′) of −22.5 mV in 0.1 M pH 7.0 phosphate buffer solution. The apparent heterogeneous electron transfer rate constants (k
s) in the Chit–MWNTs film was evaluated as 2.58 s−1 according to Laviron’s equation. The surface concentration (Γ*) of the electroactive Hb in the Chit–MWNTs film was estimated to be (2.48 ± 0.25) × 10−9 mol cm−2. Meanwhile, the Chit–MWNTs/Hb/AgNPs/GCE demonstrated excellently electrocatalytical ability to H2O2. Its apparent Michaelis–Menten constant (K
Mapp) for H2O2 was 0.0032 mM, showing a good affinity. Under optimal conditions, the biosensors could be used for the determination of H2O2 ranging from 6.25 × 10−6 to 9.30 × 10−5 mol L−1 with a detection limit of 3.47 × 10−7 mol L−1 (S/N = 3). Furthermore, the biosensor possessed rapid response to H2O2 and good stability, selectivity, and reproducibility. 相似文献
13.
Viviane Dalmoro Jo?o H. Z. dos Santos Denise S. Azambuja 《Journal of Solid State Electrochemistry》2012,16(1):403-414
Protection from corrosion of the aluminum alloy AA2024-T3 coated with a tetraethoxysilicate (TEOS)/aminotrimethyllenephosphonic
acid (ATMP) film in a 0.05-mol L−1 NaCl solution was evaluated using electrochemical impedance spectroscopy, scanning electron microscopy, energy disperse spectroscopy,
and atomic force microscopy. The present work investigates the influence of different pretreatment procedures of the alloy
surface and the ATMP concentration on the corrosion resistance of the coated samples. The undoped sol–gel coatings did not
provide adequate corrosion protection. The best corrosion protection was achieved using acetic acid pretreatment and subsequent
deposition of an ATMP-modified TEOS film with an optimal concentration of 5.00 × 10−4 mol L−1 in the deposition bath. The acetic acid pretreatment promotes a decrease in galvanic corrosion and the surface enrichment
of aluminum favoring the metalosiloxane and the metal–phosphonic bonds with increasing likely reaction sites, thus promoting
the formation of a more homogeneous and compact coating with improved resistance. 相似文献
14.
Hong-Wen Siao Shen-Ming Chen Kuo-Chiang Lin 《Journal of Solid State Electrochemistry》2011,15(6):1121-1128
A method to fabricate poly(3,4-ethylene dioxythiophene)-poly(4-styrene sulfonate)-Meldola Blue (PEDOT-PSS-MDB)-modified electrodes
had been disclosed. Firstly, the PEDOT-PSS-film-modified electrode was electrochemically prepared. Then, the PEDOT-PSS was
treated as a matrix to immobilize electroactive mediator, Meldola Blue (MDB), by means of an electrostatic interaction to
form the proposed film, PEDOT-PSS-MDB. Electrochemical properties of the proposed film exhibited surface confinement and pH
dependence. The PEDOT-PSS-MDB electrode could electrocatalytically reduce hydrogen peroxide (H2O2) with a low overpotential and showed a linear response to H2O2 in the concentration range of 5 to 120 μM, detection limit of 0.1 μM, and sensitivity of 353.9 μA mM−1 cm−2 (S/N = 3). By comparison, the electrocatalytic activity of PEDOT-PSS-MDB electrode was found superior to that of PEDOT-PSS and
MDB-PSS electrodes. It also has competitive potential as compared with other mediators, through the use of HRP to determine
H2O2. Moreover, the potential interferents such as ascorbic acid, dopamine, uric acid, and glucose were also studied for H2O2 determination by the proposed film. 相似文献
15.
This work reported for the first time the use of flow injection electrochemiluminescence (FI-ECL) sensor for the determination
of durabolin in an aqueous system based on CdTe quantum dot (QD) films. Aqueous CdTe colloidal solutions were prepared using
thioglycolic acid as a capping agent. Zetasizer Nano ZS (Malvern, UK) was employed to characterize the size of CdTe QDs. The
UV–vis and photoluminescence spectra of samples were systematically characterized. Indium tin oxide (ITO) slide glass was
modified with CdTe QDs by layer-by-layer self-assembly. CdTe QD films were packed into a homemade cell and used as a recognizer
of the FI-ECL sensor to determine durabolin. The intensive anodic ECL emission was obtained at a starting potential of +1.3 V
(vs. Ag/AgCl) in a carbonate bicarbonate buffer solution with a pH of 9.93 at an ITO electrode. The ECL intensity was correlated
linearly with the concentration of durabolin over the range of 1.0 × 10−8–1.0 × 10−5 g mL−1, and the detection limit was 2.5 × 10−9 g mL−1. The relative standard deviation for the determination of 1.0 × 10−6 g mL−1 durabolin was 1.04% (n = 11). This simple and sensitive sensor revealed good reproducibility for ECL analysis. As a result, the new FI-ECL sensor
had been successfully applied to the determination of durabolin in food samples. This strategy could be easily realized and
opened new avenues for the applications of QDs in ECL biosensing. 相似文献
16.
Determination of chromium(VI) and total chromium in water by in-electrode coulometric titration in a porous glassy carbon electrode 总被引:1,自引:0,他引:1
Chromium(VI) is determined through its direct electrochemical reduction in the bulk of a porous glassy carbon electrode. An
electrode filled with the acidified sample and Cr(VI) is reduced by means of a constant current whereas the potential of the
electrode is monitored. The limits of detection and quantification were found to be 1.9 and 6.0 μg · L−1, resp. The linear range, repeatability and reproducibility were found to be 5–500 μg · L−1, 1.2, and 1.8%, resp. The influence of Fe(III), Ca(II), Mg(II), sulphates, nitrates, humic acids and surfactants was investigated.
Total chromium was measured after chemical oxidation of Cr(III) to chromate by permanganate. The method was applied to analyses
of water samples. 相似文献
17.
Kumar S. Ashok Wang Sea-Fue Yeh Chun-Ting Lu His-Chuan Yang Jen-Chang Chang Yu-Tsern 《Journal of Solid State Electrochemistry》2010,14(11):2129-2135
In this study, stable and homogenous thin films of multiwalled carbon nanotubes (MWCNTs) were obtained on conducting surface
using ciprofloxacin (CF, fluoroquinolone antibiotic) as an effective-dispersing agent. Further, MWCNTs/CF film modified electrodes
(glassy carbon and indium tin oxide-coated glass electrode) are used successfully to study the direct electrochemistry of
proteins. Here, cytochrome C (Cyt-C) was used as a model protein for investigation. A MWCNTs/CF film modified electrode was
used as a biocompatible material for immobilization of Cyt-C from a neutral buffer solution (pH 7.2) using cyclic voltammetry
(CV). Interestingly, Cyt-C retained its native state on the MWCNTs/CF film. The Cyt-C adsorbed MWCNTs/CF film was characterized
by scanning electron microscopy (SEM), UV–visible spectrophotometry (UV-vis) and CV. SEM images showed the evidence for the
adsorption of Cyt-C on the MWCNTs/CF film, and UV–vis spectrum confirmed that Cyt-C was in its native state on MWCNTs/CF film.
Using CV, it was found that the electrochemical signal of Cyt-C was highly stable in the neutral buffer solution and its redox
peak potential was pH dependent. The formal potential (−0.27 V) and electron transfer rate constant (13 ± 1 s−1) were calculated for Cyt-C on MWCNTs/CF film modified electrode. A potential application of the Cyt-C/MWCNTs/CF electrode
as a biosensor to monitor H2O2 has been investigated. The steady-state current response increases linearly with H2O2 concentration from 2 × 10−6 to 7.8 × 10−5 M. The detection limit for determination of H2O2 has been found to be 1.0 × 10−6 M (S/N = 3). Thus, Cyt-C/MWCNTs/CF film modified electrode can be used as a biosensing material for sensor applications. 相似文献
18.
Nanostructured platinum-gold (Pt–Au) hybrid film modified glassy carbon electrode (GCE) was fabricated by electro-deposition
method in the presence of 2 × 10−4 mol l−1
l-cysteine. To examine the surface morphological analysis, the (Pt–Au) hybrid film were electrochemically deposited on transparent
semiconductor indium tin oxide (ITO) electrodes for scanning electron microscopy (SEM) and energy dispersive spectroscopy
(EDS) studies. From the SEM analysis, it was observed that the deposited nanoplatinum (250–400 nm) was formed as a cauliflower-shaped
structure with the gold nanoparticles (30–90 nm). The concentration variation of additive l-cysteine results in the formation of cauliflower-shaped platinum nanoparticles. Further, the Pt–Au hybrid film modified GCE
could be used for the detection of catecholamine neurotransmitters epinephrine (EP), norepinephrine (NEP) individually and
in the presence of ascorbic acid (AA) in pH 7 phosphate-buffered solutions (PBS). Furthermore, the proposed Pt–Au hybrid film
could be applied for the detection of epinephrine in injection solution and ascorbic acid from commercially available vitamin
C tablets. 相似文献
19.
Fenghua Liu Gaojie Xu Jinghua Wu Yuchuan Cheng Jianjun Guo Ping Cui 《Colloid and polymer science》2010,288(18):1739-1744
A kind of titanium oxide nanoparticles modified with varying amounts of oxalate group was prepared using a modified hydrolysis
method. The microstructure, dielectric properties, and electrorheological (ER) performance were investigated. The results
indicate that the oxalate group can effectively improve the dielectric properties and surface polarizability of the particles,
and the ER performance of modified titanium oxide-based ER fluid is much higher than that of pure titanium oxide-based ER
fluid. The shear stress of suitable oxalate group-modified amorphous titanium oxide-based ER fluid with a volume fraction
of 30% reaches 47.5 kPa at E = 5 kV/mm, and the current density is less than 18 μAcm−2. The yield stress can be up to 114 kPa at E = 5 kV/mm with a volume fraction of 40%. 相似文献
20.
Luciana B. O. dos Santos Carlos M. C. Infante Jorge C. Masini 《Analytical and bioanalytical chemistry》2010,396(5):1897-1903
This work describes the development and optimization of a sequential injection method to automate the determination of paraquat
by square-wave voltammetry employing a hanging mercury drop electrode. Automation by sequential injection enhanced the sampling
throughput, improving the sensitivity and precision of the measurements as a consequence of the highly reproducible and efficient
conditions of mass transport of the analyte toward the electrode surface. For instance, 212 analyses can be made per hour
if the sample/standard solution is prepared off-line and the sequential injection system is used just to inject the solution
towards the flow cell. In-line sample conditioning reduces the sampling frequency to 44 h−1. Experiments were performed in 0.10 M NaCl, which was the carrier solution, using a frequency of 200 Hz, a pulse height of
25 mV, a potential step of 2 mV, and a flow rate of 100 μL s−1. For a concentration range between 0.010 and 0.25 mg L−1, the current (i
p, μA) read at the potential corresponding to the peak maximum fitted the following linear equation with the paraquat concentration
(mg L−1): i
p = (−20.5 ± 0.3)C
paraquat − (0.02 ± 0.03). The limits of detection and quantification were 2.0 and 7.0 μg L−1, respectively. The accuracy of the method was evaluated by recovery studies using spiked water samples that were also analyzed
by molecular absorption spectrophotometry after reduction of paraquat with sodium dithionite in an alkaline medium. No evidence
of statistically significant differences between the two methods was observed at the 95% confidence level. 相似文献