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1.
A simple electrochemical method for the determination of association constants between carbohydrates and carbohydrate-binding proteins using cyclic voltammetry (CV) is described. The binding of concanavalin A (Con A) and cholera toxin (CT) to their specific α-mannose and β-galactose derivatives self-assembled on gold electrodes is electrochemically monitored with a redox probe of K3Fe(CN)6/K4Fe(CN)6. Upon binding of the proteins to the carbohydrate-modified electrodes, the redox current in CV decreases. The binding-induced change in electrochemical signal is thus used to construct Langmuir adsorption isotherm for the carbohydrate–protein interactions and to obtain the association constants. The association constants of carbohydrate–protein interactions determined by CV ((5.8 ± 1.2) × 107 M− 1 for mannose–Con A, (2.6 ± 0.5) × 108 M− 1 for galactose-CT) were in good agreement with those measured with electrochemical impedance spectroscopy and quartz crystal microbalance. 相似文献
2.
《Electrochemistry communications》2001,3(6):263-266
Vanadium pentoxide (V2O5) was electrodeposited on a poly(p-phenylene terephtalamide) (PPTA)-film coated electrode. The cyclic voltammogram of the film had a reversible redox current peak. The film was dark green in the reduced state and yellow in the oxidized state. To obtain new colour, gold was further electrodeposited on the film. Not only the redox current peak but also a new redox current shoulder appeared in the cyclic voltammogram of the obtained film, and it exhibited a multicoloured electrochromism: blackish green ↔ dark green ↔ green ↔ bright red. The red colour in the oxidized state was first obtained for the V2O5 film. The new redox current shoulder and the colour were probably due to AuyV2O5 partially formed during electrodeposition of the gold. The redox of the AuyV2O5 was accompanied by egress and ingress of Li+ ions and the new colour change. 相似文献
3.
《Electrochemistry communications》2008,10(4):582-586
This article reports a rapid method of preparing self-assembled monolayers of dodecanethiol (C12SH-SAMs) on polycrystalline gold by microwave irradiation (MWI, 650 W, duty cycle is 10%). The qualities of C12SH-SAMs were characterized by both cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results show that the C12SH-SAMs formed by MWI in 120 s (C12SH-SAMsMWI,120 s) have low ionic permeability (the differential capacitance Cd values are independent of the scan rate and phase angle at 1 Hz Φ1 Hz = 89 ± 0.9°), excellent electrochemical blocking ability towards the redox probe (the current iMWI,120 s obtained from CV is lowest when compared to other SAMs and charge transfer resistance Rct = (1.15 ± 0.19) × 106 Ω cm2), and high surface coverage (99.996 ± 0.001%). 相似文献
4.
We immobilized human cytochrome P450 (CYP), a membrane-bound enzyme, onto both smooth and nanostructured surfaces of gold electrodes via a naphthalene thiolate monolayer film. Rapid electron transfer of CYP with an electrode as a redox partner took place when the enzyme was immobilized onto an electrode surface with nanostructures. This structure was easily prepared by conventional sputtering techniques. A well-defined pair of peaks was observed at ? 0.175 V (vs. SHE) with the largest heterogeneous electron transfer rate constant of 340 s? 1 for human CYP. The positive redox potential shift of 45 mV upon drug (testosterone) binding was clearly detected, which corresponded to a change in the spin states of heme iron in CYP. The present study showed that gold sputtered surfaces are very useful for direct electron transfer reactions of human CYP isoforms. 相似文献
5.
The radiation induced degradation of 4-nitrophenol (4-NP) has been studied by gamma irradiation, while the reactivity and spectral features of the short lived transients formed by reaction with primary transient radicals at different pHs has been investigated by pulse radiolysis technique. In steady state radiolysis a dose of 4.4 k Gy is able to degrade 98% of 1×10−4 mol dm−3 4-NP. 4-NP has pKa at 7.1, above which it is present in the anionic form. At pH 5.2, •OH and N3• radicals were found to react with 4-NP with rate constants of 4.1×109 dm3 mol−1 s−1 and 2.8×108 dm3 mol−1 s−1, respectively. Differences in the absorption spectra of species formed in the reactions of 4-NP with •OH and N3• radicals suggested that •OH radicals add to the aromatic ring of 4-NP along with electron transfer reaction, whereas N3• radicals undergo only electron transfer reaction. At pH 9.2, rate constants for the reaction of •OH radicals with 4-NP was found to be higher by a factor of 2 compared to that at pH 5.2. This has been assigned to the deprotonation of 4-NP at pH 9.2. 相似文献
6.
《Electrochemistry communications》2008,10(4):587-591
This paper reports a new solvent, room-temperature ionic liquid (RTIL), for the preparation of dodecanethiol self-assembled monolayers (C12SH-SAMs) on polycrystalline gold. The quality of C12SH-SAMs was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). From CV experiments, we find that the differential capacitance Cd values of the C12SH-SAM prepared in RTIL, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6) containing 10 μL neat C12SH for 24 h (C12SH-SAMs[BMIM]PF6,10 μL,24 h) are independent of the scan rate, the effective thickness deff value and the average cant angle φ value of this monolayer are 18 ± 1 Å and 27 ± 4°, respectively. The difference value of the current density at −0.2 and 0.5 V (Δip) is only 0.73 ± 0.18 μA cm−2. EIS experiments show that the phase angle value at 1 Hz Φ1 Hz, the charge transfer resistance Rct value and surface coverage θ value of this C12SH-SAM are 88.2 ± 0.7°, 3.44 ± 1.91 MΩ cm2 and 99.998 ± 0.001%, respectively. These results indicate that high-quality C12SH-SAMs can be formed in [BMIM]PF6. In addition, the rate of formations of high-quality C12SH-SAMs in RTIL can be substantially improved by ultrasound. 相似文献
7.
Novel films consist of multi-walled carbon nanotubes (MWCNT) were fabricated by means of catalytic chemical vapor deposition (CVD) technique with decomposition of either acetonitrile (ACN) or benzene (BZ) using ferrocene (FeCp2) as catalyst. The electrochemical and thermodynamic behavior of the ferrocyanide/ferricyanide, [Fe(CN)6]3−/4− redox couple on synthesized MWCNT-based films was investigated by means of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques at T = (278.15, 283.15, 293.15, and 303.15) K. The redox couple [Fe(CN)6]3−/4− behaves quasi-reversibly on fabricated MWCNT-based films and its reversibility is enhanced upon increasing temperature. Namely, the findings establish that with the rise in temperature the barrier for interfacial electron transfer decreases, leading, consequently, to an enhancement of the kinetics of the charge transfer process. According to thermodynamics the equilibrium of the redox process is shifted towards the formation of [Fe(CN)6]3− at elevated temperatures. 相似文献
8.
Qinyan Yang Ying Liang Tianshu Zhou Guoyue Shi Litong Jin 《Electrochemistry communications》2009,11(4):893-896
Pt-nanoparticle-coated gold nanoporous film (PGNF) was synthesized via a simple nonpolluting approach and PGNF modified electrode was also constructed successfully for the rapid measurement of Escherichia coli (E. coli) in this work. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) images showed that the resulting PGNF electrode had highly ordered arrangement and large surface area. Furthermore, the electrochemical characteristics of the PGNF electrode were investigated by cyclic voltammetry (CV) and amperometric i-t curve. The PGNF electrode showed excellent electrocatalytic activity to E. coli and the current responses were in good linear from 2 × 101 cfu/ml to 1 × 106 cfu/ml with the detection limit of 10 cfu/ml (S/N = 3) without pretreatment. The high sensitivity, wider linear range and good reproducibility make this PGNF a promising candidate for portable amperometric E. coli sensor. 相似文献
9.
《Electrochemistry communications》2008,10(1):38-41
A robust and effective composite film based on gold nanoparticles (GNPs)/room temperature ionic liquid (RTIL)/multi-wall carbon nanotubes (MWNTs) modified glassy carbon (GC) electrode was prepared by a layer-by-layer self-assembly technique. Cytochrome c (Cyt c) was successfully immobilized on the RTIL-nanohybrid film modified GC electrode by electrostatic adsorption. Direct electrochemistry and electrocatalysis of Cyt c were investigated. The results suggested that Cyt c could be tightly adsorbed on the modified electrode. A pair of well-defined quasi-reversible redox peaks of Cyt c was obtained in 0.10 M, pH 7.0 phosphate buffer solution (PBS). RTIL-nanohybrid film showed an obvious promotion for the direct electron transfer between Cyt c and the underlying electrode. The immobilized Cyt c exhibited an excellent electrocatalytic activity towards the reduction of H2O2. The catalysis currents increased linearly to the H2O2 concentration in a wide range of 5.0 × 10−5– 1.15 × 10−3 M. Based on the multilayer film, the third-generation biosensor could be constructed for the determination of H2O2. 相似文献
10.
《Electrochemistry communications》2003,5(3):214-219
The electrochemical reduction of molecular oxygen (O2) has been performed at gold electrodes modified with a submonolayer of a self-assembly (sub-SAM/Au) of a thiol compound (typically cysteine (CYST)) in O2-saturated 0.5 M KOH. At bare gold electrode O2 reduction reaction proceeds irreversibly, while this reaction is totally hindered at gold electrodes with a compact structure of CYST over its surface. The partial reductive desorption of the compact CYST monolayer was achieved by controlling the potential of the CYST/Au electrode, leading to the formation of a submonolayer coverage of the thiol compound over the Au electrode surface (sub-SAM/Au), at which the CYST molecules selectively block the Au(1 0 0) and Au(1 1 0) fractions (the so-called rough domains) of the polycrystalline Au while the Au(1 1 1) component (the so-called smooth domains) remains bare (i.e., uncovered with CYST). This sub-SAM/Au electrode extraordinarily exhibits a quasi-reversible two-electron reduction of molecular oxygen (O2) in alkaline medium with a peak separation (ΔEp) between the cathodic and anodic peak potentials (Epc,Epa) of about 60 mV. The ratio of the anodic current to the cathodic one is close to unity. The formal potential (Eo′) of this reaction is found to equal −150 mV vs. Ag/AgCl/KCl(sat.). 相似文献
11.
Shengjie Peng Fangyi Cheng Jifu Shi Jing Liang Zhanliang Tao Jun Chen 《Solid State Sciences》2009,11(12):2051-2055
This paper reports on the application of cornstalks-derived high-surface-area microporous carbon (MC) as the efficient photocathode of dye-sensitized solar cells (DSCs). The photocathode, which contains MC active material, Vulcan XC–72 carbon black conductive agent, and TiO2 binder, was obtained by a doctor blade method. Electronic impedance spectroscopy (EIS) of the MC film uniformly coated on fluorine doped SnO2 (FTO) glass displayed a low charge-transfer resistance of 1.32 Ω cm2. Cyclic voltammetry (CV) analysis of the as-prepared MC film exhibited excellent catalytic activity for I3?/I? redox reactions. The DSCs assembled with the MC film photocathode presented a short-circuit photocurrent density (Jsc) of 14.8 mA cm?2, an open-circuit photovoltage (Voc) of 798 mV, and a fill factor (FF) of 62.3%, corresponding to an overall conversion efficiency of 7.36% under AM 1.5 irradiation (100 mW cm?2), which is comparable to that of DSCs with Pt photocathode obtained by conventional thermal decomposition. 相似文献
12.
Twenty-three different Rh complexes of the (NHC)RhCl(cod) and (NHC)RhCl(CO)2 type were synthesized from [RhCl(cod)]2. The electron donating nature of the NHC ligands was changed in a systematic manner. The redox potentials of the various (NHC)RhCl(cod) and the ν(CO) of the various (NHC)RhCl(CO)2 were determined. A correlation of the Rh redox potentials and the Rh ν(CO), respectively, with the related data from analogous (NHC)IrCl(cod) and (NHC)IrCl(CO)2 complexes established two linear relationships. The linear regression (R2 = 0.993) of the Rh and the Ir redox potentials results in an equation for the redox potential transformation: E1/2(Ir) = 1.016 · E1/2(Rh) ? 0.076 V. The linear regression (R2 = 0.97) of the Rh and Ir νav(CO) results in an equation for the νav(CO) transformation: νav(CO)Ir = 0.8695 · νav(CO)Rh + 250.7 cm?1. In this manner the Rh and the Ir-scale for the determination of the electron donating properties of NHC ligands are unified. 相似文献
13.
《Electrochemistry communications》2008,10(3):355-358
Gold nanorods (GNRs) were synthesized by a seed–mediated growth approach followed by TEOS polymerization leading to the formation of silica layer surrounding the gold nanorod core. TEM images showed that the silica-coated gold nanorods (GNRs@SiO2) were dispersed with an average aspect ratio of 3.1 for the GNRs cores and a uniform thickness of the silica shell. The core/shell nanocomposites were further used as efficient supports for the immobilization of hemoglobin (Hb) to fabricate a novel biosensor. The immobilized Hb showed an enhanced electron transfer for its heme Fe(III) to Fe(II) redox couple. This biosensor showed an excellent bioelectrocatalytic activity towards H2O2 with a linear range from 8.0 × 10−7 to 6.1 × 10−5 M, and the detection limit was 6.0 × 10−8 M at 3σ. The apparent Michaelis–Menten constant of the immobilized hemoglobin was calculated to be 0.13 mM. 相似文献
14.
《Vibrational Spectroscopy》2011,55(2):133-136
Surface-enhanced Raman scattering (SERS) spectra of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was obtained by employing a bi-layer gold substrate, assembled by the reduction of Au(III) over gold-seeded nanoparticles immobilized on functionalized glass substrates. The SERS signal was linear with the logarithm of the solution concentrations between 1.0 × 10−7 mol L−1 and 1.0 × 10−3 mol L−1, indicating that the bi-layer gold substrate affords a significant dynamic range for SERS, providing an excellent analytical response within this concentration range, and revealing the high sensitivity of the gold surface towards such analyte. In addition, using the same gold substrate, a similar calibration curve was obtained for crystal-violet (CV), and it was possible to identify the concentration limit corresponding to the transition from the average SERS to the nonlinear SERS response. 相似文献
15.
《Spectrochimica Acta Part B: Atomic Spectroscopy》2006,61(8):951-958
In this paper, we present experimental results for excitation coefficients of krypton atoms to several Kr and Kr+ excited levels for E/N (electric field to gas particle number density ratio usually in units of Townsend, 1 Td = 10− 21 V m2) values from 7 × 10− 20 V m2 to above 1 × 10− 17 V m2. The data have been obtained in two different parallel plate self-sustained Townsend discharge drift tubes. The spatial distribution of the emission intensities were recorded and then normalized to give excitation coefficients at the anode, by using the electron flux at this point. The values of these coefficients are placed on an absolute scale by using a standard tungsten ribbon lamp calibrated against a primary blackbody radiation standard. The ionization rates at different E/N are obtained from the spatial emission profiles.The data for atomic krypton levels 2p2, 2p3, 2p5, 2p6, 2p7, 2p8, 3p5 and 3p6 (in Paschen notation) were converted to excitation coefficients by using quenching coefficients from the literature. The emission coefficients of eight 4s24p4 (3P)5p levels of Kr+ have also been measured for E/N values from about 1 × 10− 18 V m2 up to nearly 8 × 10− 18 V m2. 相似文献
16.
《Electrochemistry communications》2007,9(4):599-604
Electrochemical deposition of PbTe from 50 mM Pb(NO3)2 + 1 mM TeO2 + 0.1 M HNO3 solution onto n-Si(1 0 0) wafers was studied using cyclic voltammetry (CV), chronoamperometry, ex situ SEM, XRD and EDX. Electrochemical behavior of n-Si(1 0 0) electrode in electrolytes 50 mM Pb(NO3)2 + 0.1 M HNO3 and 1 mM TeO2 + 0.1 M HNO3 was also studied. No underpotential deposition (UPD) of Pb and Te onto n-Si was observed in the investigated systems indicating weak Pb–Si and Te–Si interactions. Deposition of Pb and Te on n-Si occurred with overvoltage via 3D island growth. Electrosynthesis of PbTe (NaCl-like structure, a = 0.650 nm) takes place due to codeposition of Pb and Te at potentials E > EPb2+/Pb0 (lead UPD onto tellurium). Cathodic deposition of PbTe onto n-Si(1 0 0) is irreversible – there is no anodic current in the CV curve. Oxidation of PbTe on n-Si is observed only under illumination, when photoelectrons and photoholes are generated in silicon substrate. 相似文献
17.
Tungsten-containing formate dehydrogenase from Methylobacterium extorquens AM1 (FoDH1) catalyzes formate oxidation with NAD+. FoDH1 shows little direct communication with carbon electrodes, including mesoporous Ketjen Black-modified glassy carbon electrode (KB/GCE); however, it shows well-defined direct electron transfer (DET)-type bioelectrocatalysis of carbon dioxide reduction, formate oxidation, NAD+ reduction, and NADH oxidation on gold nanoparticle (AuNP)-embedded KB/GCE treated with 4-mercaptopyridine. Microscopic measurements reveal that the AuNPs (d = 5 nm) embedded on the KB surface are uniformly dispersed. Electrochemical data indicate that the pyridine moiety on the AuNPs plays important roles in facilitating the interfacial electron transfer kinetics and increasing the probability of productive orientation of FoDH1. The formal potential of the electrochemical communication site, which is most probably an ion‑sulfur cluster, is evaluated as − 0.591 ± 0.005 V vs. Ag | AgCl | sat. KCl from Nernst analysis of the steady-state catalytic waves. 相似文献
18.
A glassy carbon electrode (GCE) modified with internal-electrolysis deposited gold nanoparticles (AuNPsied) was applied to sensitively and selectively detect As(III) by anodic stripping linear sweep voltammetry (ASLSV). The AuNPsied/GCE was prepared based on the redox replacement reaction between a supporting-electrolyte-free aqueous HAuCl4 and a copper sheet in saturated KCl separated by a salt bridge. Under optimum conditions (0.5 M aqueous H2SO4, 300-s preconcentration at − 0.4 V), the ASLSV peak current for the As(0)–As(III) oxidation responded linearly to As(III) concentration from 0.02 to 3 μM with a limit of detection (LOD) of 0.9 nM (0.07 μg L− 1) (S/N = 3), while that for the As(III)–As(V) oxidation was linear with As(III) concentration from 0.02 to 1 μM with a LOD of 4 nM (0.3 μg L− 1) (S/N = 3). An appropriate high-scan-rate for ASLSV can enhance both the sensitivity and signal-to-noise ratio. This method was applied for analyses of As(III) in real water samples. 相似文献
19.
Kyle M. Lancaster James B. Gerken Alec C. Durrell Joshua H. Palmer Harry B. Gray 《Coordination chemistry reviews》2010,254(15-16):1803-1811
The properties of RuII complexes involving the imidazole moiety are discussed. Complexes [Ru(bpy)2(L)]2+ [bpy = 2,2′-bipyridine, L = 2-(2′-pyridyl)imidazole (2-pimH) and 4-(2′-pyridyl)imidazole (4-pimH)] have been synthesized and fully characterized. Reduction potentials are 0.76 V vs. Fc+/Fc0 for both complexes in acetonitrile solution, and the deprotonated complexes undergo irreversible electrochemical oxidation at 0.38 V vs. Fc+/Fc0. Density functional theory (DFT) calculations suggest that oxidation of the protonated complexes is primarily metal-based and that of the deprotonated complexes is ligand-centered. The pKa of the 4-pimH complex was found to be 9.7 ± 0.2; the pKa of the 2-pimH complex is 7.9 ± 0.2. Luminescence lifetimes (L = 4-pimH, 277 ns; 2-pimH, 224 ns; 4pim?, 40 ns; 2pim?, 34 ns in 5% methanol/water solution) combined with quantum yield data and acid–base behavior suggest that the non-coordinated imidazole nitrogen tunes deactivation pathways. 相似文献
20.
We determined apparent molar volumes V? at 298.15 ? (T/K) ? 368.15 and apparent molar heat capacities Cp,? at 298.15 ? (T/K) ? 393.15 for aqueous solutions of HIO3 at molalities m from (0.015 to 1.0) mol · kg?1, and of aqueous KIO3 at molalities m from (0.01 to 0.2) mol · kg?1 at p = 0.35 MPa. We also determined V? at the same p and at 298.15 ? (T/K) ? 368.15 for aqueous solutions of KI at m from (0.015 to 7.5) mol · kg?1. We determined Cp,? at the same p and at 298.15 ? (T/K) ? 393.15 for aqueous solutions of KI at m from (0.015 to 5.5) mol · kg?1, and for aqueous solutions of NaIO3 at m from (0.02 to 0.15) mol · kg?1. Values of V? were determined from densities measured with a vibrating-tube densimeter, and values of Cp,? were determined with a twin fixed-cell, differential temperature-scanning calorimeter. Empirical functions of m and T were fitted to our results for each compound. Values of Ka, ΔrHm, and ΔrCp,m for the proton ionization reaction of aqueous HIO3 are calculated and discussed. 相似文献