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1.
We report an electrochemical transducer based on an organic double‐gate transistor. The bottom‐gate is given by a p‐doped silicon substrate, which is covered by 300 nm thermal oxide. A 20 nm pentacene film acts as the semiconducting layer, and a 50 nm tetratetracontane (TTC) alkane film is used as a top‐gate dielectric. An aqueous ionic solution acts as top‐gate. We record the transistor transfer characteristics by variation of the electrolyte potential via a Ag/AgCl electrode for various bottom‐gate settings. A change of the electrolyte potential results in a change of the transistor current and the characteristic behaviour of the device is in good agreement with the expected behaviour of a double‐gate transistor. The top‐gate capacitance of the alkane layer is as high as 2.6×10?8 F cm?2 determined by impedance measurements, indicating that TTC is a good choice as an organic top‐gate dielectric. The suitability of this transducer configuration for sensing in aqueous media is demonstrated by the detection of hexanoic acid and stearic acid molecules adsorbing to the alkane interface, respectively. We show that the transducer easily achieves a concentration sensitivity in the range of 100 nM. 相似文献
2.
Eric B. Kalman Olivier Sudre Ivan Vlassiouk Zuzanna S. Siwy 《Analytical and bioanalytical chemistry》2009,394(2):413-419
Control of ionic transport through nanoporous systems is a topic of scientific interest for the ability to create new devices
that are applicable for ions and molecules in water solutions. We show the preparation of an ionic transistor based on single
conical nanopores in polymer films with an insulated gold thin film “gate.” By changing the electric potential applied to
the “gate,” the current through the device can be changed from the rectifying behavior of a typical conical nanopore to the
almost linear behavior seen in cylindrical nanopores. The mechanism for this change in transport behavior is thought to be
the enhancement of concentration polarization induced by the gate.
Figure
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
3.
Details of the standardization of the reference electrode Hg/HgCl2(s) versus the SHE by a potentiometric method using two acids (viz., perchloric and 2,5-dichlorobenzene-sulfonic acids) in 80
mass % propylene carbonate (PC) + p-xylene (PX), are presented. Using this reference electrode, the standard electrode potential of the quinhydrone electrode
was determined in this medium. The reference electrode potential and the standard electrode potential of the quinhydrone electrode
were found to be (0.277±0.003) and (0.760±0.003) V versus SHE in 80 mass % PC + PX at 25 °C, respectively. The voltammetric
behavior of the quinhydrone system in this medium was investigated at a micro platinum electrode against a non-aqueous double-junction
Ag/AgCl reference electrode. The standard electrode potential of the quinhydrone system was also calculated using voltammetric
and chronocoulometric data that is comparable with the value obtained by potentiometry. 相似文献
4.
The structure of water solubilized by reverse aggregates of calcium bis(2-ethylhexyl) sulfosuccinate in deuterobenzene and
toluene has been probed by Fourier transform-IR and 1H NMR spectroscopies. The νOD band of solubilized HOD (4% D2O in H2O) has been recorded as a function of the [water]/[surfactant] molar ratio, W/S. Curve fitting of this band showed the presence
of a main peak at 2550 ± 13 cm−1 and a small one at 2405 ± 15 cm−1. As a function of increasing W/S, the frequency of the main peak decreases, its full width at half-height increases, and
its area increases linearly. The 1H NMR chemical shift of solubilized H2O–D2O mixtures at W/S = 18.1 has been measured as a function of the deuterium content of the aqueous nanodroplet. These data were
used to calculate the so-called “fractionation factor” of the aggregate-solubilized water, the value of which was found to
be unity. The results of both techniques show that reverse aggregate-solubilized water, although different from bulk water,
does not seem to coexist in “layers” of different degrees of structure, as suggested, for example by the two-state water-solubilization
model.
Received: 12 July 1999/Accepted: 30 August 1999 相似文献
5.
Antonio Doménech-Carbó Teresa Doménech-Carbó Carmen Saurí-Peris José Vicente Gimeno-Adelantado Francisco Bosch-Reig 《Mikrochimica acta》2005,152(1-2):75-84
Electrochemical identification of natural insoluble curcuma and safflower dyes in microsamples usable for microchemical examination
of works of art and archaeological artifacts via solid state voltammetry is described. Upon attachment to paraffin-impregnated
graphite electrodes in contact with aqueous acetate and phosphate buffers, curcuma and safflower yield well-defined square
wave voltammetric responses with well-defined oxidation peaks in the potential region of +0.65–+0.25 V vs. AgCl/Ag allowing
for unambiguous identification of such dyes in microsamples. 相似文献
6.
Mustafa Özden Ergun Ekinci A. Ersin Karagözler 《Journal of Solid State Electrochemistry》1998,2(6):427-431
A polyindoline permselective polymer film was readily synthesized by an electrochemical polymerization of indoline in an
aqueous solution of KCl at a potential of 0.4 V vs Ag/AgCl. The amperometric responses of the polyindoline film-coated platinum
electrodes to electroactive (ascorbic acid, oxalic acid and hydrogen peroxide) and non-electroactive (lactose, sucrose and
urea) substances were measured at a potential of 0.7 V. Effects of various variables such as film thickness, concentrations
of monomer and electrolyte, and pH on the permselective behavior of the polymeric membrane were systematically investigated
and the optimal values were determined. It was found that permselective polyindoline-coated electrodes prepared in this one-step
procedure permitted hydrogen peroxide oxidation while it prevented interference due to oxidizable species such as ascorbic
acid and oxalic acid. As a result, it is believed that this polymeric membrane, owing to its permselective character, can
be used as the protective material in the construction of hydrogen peroxide-based biosensors.
Received: 10 November 1997 / Accepted: 27 January 1998 相似文献
7.
Hadi Beitollahi Mohammad Mazloum Ardakani Hossein Naeimi Bahram Ganjipour 《Journal of Solid State Electrochemistry》2009,13(3):353-363
The preparation and electrochemical characterization of a carbon nanotube paste electrode modified with 2,2′-[1,2-ethanediylbis
(nitriloethylidyne)]-bis-hydroquinone, referred to as EBNBH, was investigated. The EBNBH carbon nanotube paste electrode (EBNBHCNPE)
displayed one pair of reversible peaks at E
pa = 0.18 V and E
pc = 0.115 V vs Ag/AgCl. Half wave potential (E
1/2) and ΔE
p were 0.148 and 0.065 V vs Ag/AgCl, respectively. The electrocatalytic oxidation of ascorbic acid (AA) has been studied on
EBNBHCNPE, using cyclic voltammetry, differential pulse voltammetry and chronoamperometry techniques. It has been shown that
the oxidation of AA occurs at a potential where oxidation is not observed at the unmodified carbon paste electrode. The heterogeneous
rate constant for oxidation of AA at the EBNBHCNPE was also determined and found to be about 1.07 × 10−3 cm s−1. The diffusion coefficient of AA was also estimated as 5.66 × 10−6 cm2 s−1 for the experimental conditions, using chronoamperometry. Also, this modified electrode presented the property of electrocatalysing
the oxidation of AA and uric acid (UA) at 0.18 and 0.35 V vs Ag/AgCl, respectively. The separations of anodic peak potentials
of AA and UA reached 0.17 V. Using differential pulse voltammetry, the calibration curves for AA and UA were obtained over
the range of 0.1–800 μM and 20–700 μM, respectively. With good selectivity and sensitivity, the present method provides a
simple method for selective detection of AA and UA in biological samples. 相似文献
8.
The electrophoretic mobility of a poly(N-isopropylacrylamide) microgel containing carboxylic groups has been measured as a function of the ionic strength, between
0.1 and 100 mM NaCl, over the temperature range 2545 ∘C. The mobility data obtained have been evaluated using different models, including the porous-sphere, the soft-plate and
the soft-sphere models as well as the hard-sphere model developed by Henry and later refined by O'Brien and White. The “porous”
or “soft” behaviour is evident at lower temperatures, whereas at higher temperatures none of the models can fully explain
the observed behaviour. It is suggested that the discrepancies at higher temperatures can be partly ascribed to the neglect
of the relaxation effect in the “soft” models.
Received: 30 June 1999/Accepted in revised form: 12 October 1999 相似文献
9.
Ewa Bobrowska-Grzesik 《Mikrochimica acta》2001,136(1-2):31-34
Derivative spectrophotometry was applied for the simultaneous determination of amoxycillin and clavulanic acid in pharmaceutical
preparations: “Augmentin” inj. and tablets and “Amoksiklav” drops and tablets, in solutions after hydrolysis with sodium hydroxide.
As the absorption spectra overlap strongly (amoxycillin λmax = 247 nm and 290 nm, clavulanic acid λmax = 258 nm) the first and the second derivative spectrophotometric procedure was elaborated for their determination. Amoxycillin
was determined at λ = 257.9 nm (1-st derivative spectra) or λ = 273 nm (2-nd derivative) while clavulanic acid at λ = 280.3 nm
(1-st derivative) or λ = 285 nm (2-nd derivative spectra). The Beer’s law is obeyed in the range of 0.004–0.04 mg/ml for amoxycillin
and 0.002–0.02 mg/ml for clavulanic acid.
Received December 6, 1999. Revision August 1, 2000. 相似文献
10.
Giorgio Papeschi Stefano Mancuso Anna Maria Marras 《Journal of Solid State Electrochemistry》2000,4(6):325-329
The electrochemical behaviour of a Cu/CuSe electrode was studied in order to define its selectivity towards cupric ions,
Nerstian response, limit of detection and response time. The chalcogenide electrode was prepared by cathodic deposition of
Se and subsequent formation of a thin layer of CuSe on a copper substrate. A Cu/CuSe microelectrode was prepared using copper
wire 75 μm in diameter. The dimensions and response time (<0.5 s) allowed use of this electrode in the “vibrating probe method”
with the aim of measuring net influxes as well as effluxes of copper(II) ions in Olea europaea roots. The electrode potential was measured along the root at a distance of 5 μm from the surface for 5 s, and then again
for 5 s at a distance of 55 μm, moving the microelectrode with respect to the root surface by steps with a frequency of 0.1 Hz.
The potentials measured at the two extremes of vibration were then converted to copper(II) concentrations. Substitution of
these values in Fick's law yields the flux, assuming the diffusion constant D for copper ions in aqueous solutions. The results enabled us to detect copper(II) fluxes as small as 0.05 pmol cm−2 s−1. Copper(II) influx showed marked spatial and temporal features: it was highest at about 1.5 mm from the root apex and exhibited
an oscillatory pattern in time.
Received: 29 September 1999 / Accepted: 11 January 2000 相似文献
11.
Characterization of groundwater humic and fulvic acids of different origin by GPC with UV/Vis and fluorescence detection 总被引:1,自引:0,他引:1
R. Artinger G. Buckau J. I. Kim S. Geyer 《Fresenius' Journal of Analytical Chemistry》1999,364(8):737-745
Gel permeation chromatography (GPC) was applied for recognizing the origin of groundwater humic and fulvic acids. GPC was
performed with Fraktogel TSK HW-50 in 0.1 M NaCl, pH 8.5 (0.05 M phosphate buffer), 1 mM EDTA, with 10% by volume methanol
added. Humic substances from groundwaters and sediments of four different aquifer systems in Germany were isolated, purified
and characterized. Both UV/Vis and fluorescence detection were applied. UV/Vis detection was found to be more powerful in
identifying differences between the various humic and fulvic acids. The four aquifer systems investigated (“Gorleben”, “Fuhrberg”,
“Franconian Albvorland” and “Munich”) differed from one another with respect to hydrological and geochemical conditions. The
results showed that the GPC-elution behavior reflects the geochemical environment and origin (source material and generation
process) of aquatic humic and fulvic acids.
Received: 17 November 1998 / Revised: 18 March 1999 / Accepted 23 March 1999 相似文献
12.
The stability of poly(N-methylaniline) (PNMA) as electrode material has been studied in aqueous solutions of sulfuric acid with the use of electrochemical
and in situ Raman spectroscopic techniques. It has been shown that the electrochemical decomposition of electrodeposited PNMA
films follows a first-order reaction kinetics. The decomposition rate constants vary between 1.2 × 10−5 and 2.0 × 10−3 s−1 for electrode potential varying between 0.2 and 1.0 V vs Ag/AgCl, respectively. In situ Raman spectroscopy has been applied
in obtaining kinetic data at selected electrode potentials, and good correlation of these data with the corresponding data
obtained by cyclic voltammetry has been found. As compared to polyaniline, the decomposition of PNMA proceeds at nearly the
same rate at electrode potentials not exceeding 0.5 V. The decomposition of PNMA proceeds faster within the potential limits
of 0.5 to 0.8 V and slower at electrode potentials exceeding 0.8 V as compared to polyaniline.
This article is dedicated to Professor Algirdas Vaškelis (Institute of Chemistry, Vilnius, Lithuania) on the occasion of his
70th birthday and in honour of his contributions to electrochemistry and physical chemistry. 相似文献
13.
Conducting polypyrrole (PPy) and poly(pyrrole-2,6-dimethyl-β-cyclodextrin) [poly(Py-β-DMCD)] films were prepared by electrode
potential cycling on a gold electrode in aqueous and nonaqueous (acetonitrile) electrolyte solutions containing lithium perchlorate.
The resulting products were characterized with cyclic voltammetry, in situ UV–Vis spectroscopy, and in situ conductivity measurements.
For the electrosynthesis of poly(Py-β-DMCD), a (1:1) (mole–mole) (Py-β-DMCD) supramolecular cyclodextrin complex of pyrrole
previously characterized with proton NMR spectroscopy was used as starting material. A different cyclic voltammetric behavior
was observed for pyrrole and the poly(Py-β-DMCD) complex in aqueous and nonaqueous solutions during electrosynthesis. The
results show that in both solutions in the presence of cyclodextrin, the oxidation potential of pyrrole monomers increases.
However, the difference of oxidation potentials for films prepared in aqueous solution is larger than for the films prepared
in nonaqueous solution. In situ conductivity measurements of the films show that films prepared in acetonitrile solution are
more conductive than those synthesized in aqueous solutions. Maximum conductivity can be observed for PPy and poly(Py-β-DMCD)
films prepared in nonaqueous solution in the range of 0.10 < E
Ag/AgCl < 0.90 V and 0.30 < E
Ag/AgCl < 0.90 V, respectively. In situ UV–Vis spectroelectrochemical data for both films prepared potentiodynamically by cycling
the potentials from −0.40 < E
Ag/AgCl < 0.90 V in nonaqueous solutions are reported.
This paper is dedicated to Prof. Alan Bond on the occasion of his 65th birthday in recognition of his numerous contributions
toward electrochemistry. 相似文献
14.
The work presented in this paper deals with the combination of capillary electrophoresis (CE) with electrospray mass spectrometry (MS) for the determination of drug residues in water. CE/MS methods have been developed based on either aqueous or non-aqueous ammonium acetate solutions as the carrier electrolyte for the separation of selected drugs. The different separation conditions were compared in terms of selectivity and detection limits; both aqueous and non-aqueous CE proved to be suitable for the present analytical task, exhibiting detection limits between 3 and 93 μg/dm3 (injected standard concentration) corresponding to concentrations between 5 and 19 ng/dm3 in the sample. A combination of liquid-liquid extraction and solid-phase extraction was investigated for sample pretreatment, yielding enrichment factors of 10000. The applicability of CE/MS was demonstrated for the analysis of several river water samples. 相似文献
15.
A polycarbazole conducting polymer transistor has been constructed having the dimensions 1 cm × 2 cm × 1 mm. Polycarbazole
film used here has a redox potential of 1.30 V. Polymer-coated platinum plates were used as the source and drain. The inter-electrode
spacing of the device is typically of the order of 200–500 μm to minimise the internal resistance. The high saturation current
region of the transistor in the most positive bias voltage (1.3 V), with negligible hysteresis and greater stability, appears
to give a device that is superior to other conducting polymer transistors.
Received: 27 May 1997 / Accepted: 17 September 1997 相似文献
16.
Electrode-supported hydrogels were conferred with the biospecificity of enzymes during the process of electropolymerization
to give rise to a class of bioactive, stimuli-responsive co-joined interpenetrating networks of inherently conductive polymers
and highly hydrated hydrogels. Glucose responsive biotransducers were prepared by potentiostatic electropolymerization [750 mV
vs. Ag/AgCl (3 M KCl)] of pyrrole at Poly(hydoxyethyl methacrylate)-based hydrogel-coated Pt micro-electrodes (Φ = 100 μm) from aqueous solutions of pyrrole and glucose oxidase (GOx; 0.4 M pyrrole, 1.0 mg/ml GOx) to 1.0 and 10.0 mC/cm2. Polypyrrole was them over-oxidized by cyclic voltammetry (0–1.2 V vs. Ag/AgCl, 40 cycles in PBKCl, pH = 7.0). Biotransducers
were stored at 4 °C in PBKCl for up to 18 days. Amperometric dose–response at 0.4 V vs. Ag/AgCl followed by Lineweaver–Burk
analysis produced enzyme kinetic parameters as a function of electropolymerization charge density and storage time. Apparent
Michaelis constant (K
Mapp) increased from 18.6–152.0 mM (1.0 mC/cm2) and from 2.7–6.1 mM (10.0 mC/cm2). Biotransducer sensitivity increased to 21.2 nA/mM after 18 days and to 12.8 pA/mM after 10 days for the 1.0 and 10.0 mC/cm2 membranes, respectively. Maximum current, I
max, also increased over time to 2.7 nA (1.0 mC/cm2) and to 170 pA (10.0 mC/cm2). Electropolymerization of polypyrrole is shown to be an effective means for imparting bioactivity to a hydrogel-coated microelectrode.
GOx was shown to be stabilized and to increase activity over time within the electroconductive hydrogel. 相似文献
17.
Josep M. Oliva 《Theoretical chemistry accounts》1999,103(1):1-8
Modern valence-bond theory, in its spin-coupled form, is used to study the electronic structure of the transition structures
in the Cope rearrangement. It is found that the transition structure described by a “chair” geometry with a “6-in-6” CASSCF/6-31G* wave function is clearly aromatic while the CASSCF/6-31G*“boat” transition structure corresponds more closely to two weakly interacting allyl radicals. Moreover, there is a striking
resemblance between the CASSCF chair transition structure and the benzene molecule, arising from the modern valence-bond analysis
in terms of Rumer spin functions. In agreement with previous works, dynamical correlated wave functions show shorter interallylic
distances in the optimized transitions structures. The use of spin-coupled wave functions on the latter geometries results
in diradical and aromatic character for the chair and boat transition structures, respectively.
Received: 13 October 1998 / Accepted: 30 December 1998 / Published online: 7 June 1999 相似文献
18.
Solid-state potentiometric sensors based on the chemical modulation of the work function of organic semiconductors are discussed.
The theory of the chemical work function modulation is briefly reviewed. There are several sensor configurations, in which
this transduction principle can be employed. First is the Kelvin probe, second is the chemically sensitive field-effect transistor
in which the conventional metal gate of the silicon-based transistor has been replaced by an organic semiconductor. Chemical
modulation of work function enters also into the operation of the third type of sensor discussed in this review, on “organic
field-effect transistor”. It is shown that in reality such sensors are “field-modulated chemiresistors”, rather than potentiometric
sensors. 相似文献
19.
Summary. The work presented in this paper deals with the combination of capillary electrophoresis (CE) with electrospray mass spectrometry
(MS) for the determination of drug residues in water. CE/MS methods have been developed based on either aqueous or non-aqueous
ammonium acetate solutions as the carrier electrolyte for the separation of selected drugs. The different separation conditions
were compared in terms of selectivity and detection limits; both aqueous and non-aqueous CE proved to be suitable for the
present analytical task, exhibiting detection limits between 3 and 93 μg/dm3 (injected standard concentration) corresponding to concentrations between 5 and 19 ng/dm3 in the sample.
A combination of liquid-liquid extraction and solid-phase extraction was investigated for sample pretreatment, yielding enrichment
factors of 10000. The applicability of CE/MS was demonstrated for the analysis of several river water samples.
Received August 25, 2000. Accepted October 17, 2000 相似文献
20.
H. Karimi-Maleh A. A. Ensafi A. R. Allafchian 《Journal of Solid State Electrochemistry》2010,14(1):9-15
A ferrocenedicarboxylic acid modified carbon paste electrode was constructed and used as a fast and sensitive tool for the
determination of captopril at trace level. It has been shown by direct current cyclic voltammetry and double step chronoamperometry
that ferrocenedicarboxylic acid can catalyze the oxidation of captopril in aqueous buffer solution and produces a sharp oxidation
peak current at about +0.49 vs. Ag/AgCl reference electrode. The square wave voltammetric peak currents of the electrode increased
linearly with the corresponding captopril concentration in the range of 3.0 × 10−7–1.4 × 10−4M with a detection limit of 9.1 × 10−8 M. The influence of pH and potential interfering substances on the determination of captopril were studied. Electrochemical
impedance spectroscopy was used to study the charge transfer properties at the electrode–solution interface. Finally, the
sensor was examined as a selective, simple, and precise new electrochemical sensor for the determination of captopril in real
samples, such as drug and urine, with satisfactory results. 相似文献