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1.
Chao-Yin Kuo 《Desalination》2009,249(2):781-785
This study compares aqueous copper (II) adsorbed onto as-grown and modified carbon nanotubes (CNTs), using H2SO4 and H2SO4/KMnO4 processes. H2SO4 and H2SO4/KMnO4 modifications reduced pHiep and Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed that some functional groups were formed on modified CNTs. The adsorption capacity of copper (II) onto modified CNTs was greater than that of as-grown CNTs, especially at pH 6. The results demonstrate that the modified processes increased the adsorption capacity because the functional groups were generated on the modified surfaces of the CNTs. Additionally, the adsorption capacity of copper (II) onto as-grown and modified CNTs both increased with temperature, and the results indicated that the Langmuir isotherm fitted the experimental data well. Simulation results indicated that the ΔH0 values of as-grown, H2SO4-modified CNTs and H2SO4/KMnO4-modified CNTs were 4.83, 14.37 and 29.92 kJ/mol, respectively. Based on ΔH0, the adsorption of Cu2+ onto H2SO4/KMnO4-modified CNTs is suggested to proceed simultaneously by physisorption and chemisorption but that onto as-grown and H2SO4-modified CNTs may proceed only by physisorption. 相似文献
2.
Weihua Guo Lin Xu Bingbing Xu Yanyan Yang Zhixia Sun Shuping Liu 《Journal of Applied Electrochemistry》2009,39(5):647-652
Keggin-type polyoxometalate (H4SiMo12O40) and carbon nanotubes (CNTs) coated by poly(allylamine hydrochloride) (PAH) were alternately deposited on glassy carbon (GC)
electrodes by an electrochemical growth method in acidic aqueous solution. The preparation of the film electrode was simple
and convenient. Thus-prepared multilayer films and the electrochemical behavior of the composite film modified electrode were
characterized by UV–vis spectroscopy and cyclic voltammetry. It was shown that the multilayer films are uniform and stable.
The resulting multilayer film modified electrode behaves as an electrochemical sensor because of its low overpotential for
the catalytic reduction of S2O8
2− and NO2
− in acidic aqueous solution. 相似文献
3.
Surface functionalised carbon nanoparticles of ca. 8 nm diameter co-assemble with chitosan into stable thin film electrodes at glassy carbon surfaces. Robust electrodes for application in sensing or electrocatalysis are obtained in a simple solvent evaporation process. The ratio of chitosan binder backbone to carbon nanoparticle conductor determines the properties of the resulting films. Chitosan (a poly-d-glucosamine) has a dual effect (i) as the binder for the mesoporous carbon composite structure and (ii) as binding site for redox active probes. Physisorption due to the positively charged ammonium group (pKA ≈ 6.5) occurs, for example, with anionic indigo carmine (a reversible 2e−-2H+ reduction system in aqueous media). Chemisorption at the amine functionalities is demonstrated with 2-bromo-methyl-anthraquinone in acetonitrile (resulting in a reversible 2e−-2H+ anthraquinone reduction system in aqueous media). Redox processes within the carbon nanoparticle-chitosan films are studied and at sufficiently high scan rates diffusion of protons (buffer concentration depended) is shown to be rate limiting. The chemisorption process provides a much more stable interfacial redox system with a characteristic and stable pH response over a pH 2-12 range. Chemisorption and physisorption can be employed simultaneously in a complementary binding process. 相似文献
4.
Self-assembled monolayers (SAMs) obtained by adsorption of n-organothiols molecules have been formed onto polycrystalline copper surfaces in order to build up barrier films protecting copper from oxidation. In this context, formation of n-dodecanethiol (DT), (3-mercaptopropyl)trimethoxysilane (MPTS) and 11-perfluorobutylundecanethiol (F4H11) monolayers has been elaborated on copper and evaluated by X-ray photoelectron spectroscopy while polarization and cyclic voltammetry curves were used to compare the inhibition efficiency of the three organic coatings. Furthermore, atomic absorption spectrometry measurements were carried out in domestic water and in NaCl 0.5 M solutions in order to evaluate and quantify the dissolution of copper electrodes before and after protection. Results showed evidences that, among the three organic compounds assessed, F4H11 is the most suitable candidate to slow down the copper oxidation process. 相似文献
5.
Chehung Wei Chao-I Wang Fong-Cheng Tai Kuen Ting Rwei-Ching Chang 《Diamond and Related Materials》2010,19(5-6):562-566
The carbon nanotubes (CNTs) doped diamond like carbon films were carried out by spinning coating multi-walled carbon nanotubes (CNTs) on silicon covered with diamond like carbon films via PECVD with C2H2 and H2. The results show that the ID/IG and sp2/sp3 ratios are proportional to the CNT contents. For wettability and hydrogen content, the increase of CNT content results in more hydrophobic and less hydrogen for CNT doped DLC films. As for mechanical properties, the hardness and elastic modulus increases linearly with increasing CNT content. The residual stress is reduced for increasing CNT content. As for the surface property, the friction coefficient is reduced for higher CNT content. For CNT doped DLC films, the inclusion of horizontal CNT into DLC films increases the hardness, elastic modulus and reduces the hydrogen content, friction coefficient and residual stress. Like the light element and metal doping, the CNT doping has effects on the surface and mechanical properties on DLC which might be useful to specific application. 相似文献
6.
Adsorption of aqueous cadmium (II) onto modified multi-walled carbon nanotubes following microwave/chemical treatment 总被引:1,自引:0,他引:1
This study evaluates the aqueous cadmium (II) adsorption efficiency of as-grown carbon nanotubes (CNTs) and of those modified by microwave (MW)/H2SO4 and MW/H2SO4/KMnO4 processes. The surface area, pHiep, and FTIR spectra of CNTs were, before and after modification, compared. Aromatic groups, carbonyl groups and hydroxyl groups were herein detected on the surfaces of MW/H2SO4 and MW/H2SO4/KMnO4-modified CNTs. At a particular pH, the adsorption capacity of Cd2+ of the MW/H2SO4/KMnO4-modified CNTs exceeded that of MW/H2SO4-modified CNTs and as-grown CNTs. The kinetic analyses of adsorption were performed and a pseudo second-order model accurately captured the adsorption kinetics. This study suggests that MW/H2SO4 and MW/H2SO4/KMnO4 modification not only increased the area of active adsorption sites of CNTs but also reduced the modification period by microwave heating. 相似文献
7.
Marta Pérez-Morales 《Electrochimica acta》2009,54(6):1791-63
In this work, ITO electrodes have been modified by means of the oxidative electrodeposition of two different cobalt porphyrins, CoTSPP and CoTMPyP, and the composition of such deposits have been studied by visible and reflection-FTIR spectroscopies. The data indicate that the porphyrin deposits are formed by a mixture of cobalt hydroxides, β-Co(OH)2 and α-Co(OH)2, and the porphyrin ring as radical. Moreover, the porphyrin electrodeposits absorb molecular oxygen as peroxo species (O22−), which has been detected in the films by IR spectroscopy, and which acts as a bridge between Co atoms (Co-O-O-Co). Also, monolayers containing a viologen derivative have been transferred onto the porphyrin-MIE (MIE, modified ITO electrode) by using the LB technique, and its redox process has been investigated. The results show an excellent mediator character of both cobalt electrodeposits throughout the viologen redox processes. Furthermore, the Co-porphyrin electrodeposits store atmospheric oxygen in a ratio proportional to the deposited porphyrin amount. This oxygen can be totally released from the porphyrin film via the electrocatalytic action of the viologen monolayer on top. 相似文献
8.
The direct electrochemistry of cytochrome C can be performed in weak acidic and basic aqueous solutions. Cytochrome C can be deposited as a stable and electrochemically active film on a deoxyribonucleic acid (DNA) modified glassy carbon electrode. These films can also be produced on gold, platinum, and transparent semiconducting tin oxide electrodes. Two-layer modified electrodes containing cytochrome C and a DNA film were prepared by the deposition of cytochrome C on a DNA film modified electrode. The cytochrome C/DNA film was electrocatalytically oxidation active for l-cysteine in a pH 8.3 tris(hydroxymethyl)aminomethane (TRIS)-buffered aqueous solution through both FeIII and FeIV species. The electrocatalytic oxidation current developed from the anodic peak of the redox couple. The electrocatalytic oxidation properties of ascorbic acid, NH2OH, N2H4, and SO32− by a cytochrome C/DNA film were also determined, and shown to be electrocatalytically active. An electrochemical quartz crystal microbalance, cyclic voltammetry, and direct spectroelectrochemistry were used to study in situ DNA deposition on a gold disc electrode and cytochrome C deposition on DNA/Au and DNA/GC films. The direct electrochemistry of cytochrome C can also be performed, and it can be deposited as a stable and electrochemically active film on polyvinyl sulfonate, polystyrene sulfonate, TiO2, and polyethylene glycol modified glassy carbon electrodes. The results show that cytochrome C interacts with, and deposits on, a DNA film modified electrode, and that the cytochrome C (FeIII) oxidized form is more easily deposited on a DNA film than the cytochrome C (FeII) reduced form. 相似文献
9.
Pyridine‐polybenzimidazole (PyPBI) films of different thickness (∼1.0–2.4 nm) are wrapped on the surfaces of multi‐walled carbon nanotubes (CNTs). To prepare Pt on PyPBI/CNT (Pt‐PyPBI/CNT) catalysts, Pt4+ ions are immobilized on these PyPBI wrapped CNTs (PyPBI/CNTs) via Lewis acid‐base coordination between Pt4+ and :N‐ of imidazole groups, followed by reducing Pt4+ to Pt nanoparticles. The influence of PyPBI film thickness on the Pt particle size, loading and electrochemical surface area, respectively, of Pt‐PyPBI/CNTs is investigated. Fuel cell performances of the PBI/H3PO4 based membrane electrode assemblies (MEAs) prepared from these Pt‐PyPBI/CNT catalysts are also evaluated at 160 °C with unhumidified H2/O2 gases. Among the catalysts, the Pt‐PyPBI/CNT catalyst with a PyPBI film thickness of ∼1.6 nm (which is around half of the Pt particle size), a Pt loading of ∼44 wt.%, and a Pt particle size of ∼3.3 nm exhibits the best fuel cell performance. 相似文献
10.
Comparison with as-grown and microwave modified carbon nanotubes to removal aqueous bisphenol A 总被引:1,自引:0,他引:1
Chao-Yin Kuo 《Desalination》2009,249(3):976-982
This study utilized carbon nanotubes (CNTs) to remove bisphenol A (BPA) from aqueous solution. The surfaces of CNTs were modified by SOCl2/NH4OH under microwave irradiation. The surface characteristics of as-grown and modified CNTs were analyzed by measuring zeta potential, and using a scanning electron microscope, a surface area analyzer and a Fourier transform infrared spectroscope. The specific surface area of modified CNTs exceeded that of as-grown CNTs. The pHiep values of as-grown CNTs and modified CNTs were determined to be 4.3 and 6.5, respectively. Some amine functionalities were formed on the surface of modified CNTs; therefore, the surface of the modified CNTs contained more positive charges than that of the as-grown CNTs. The adsorption kinetics were examined using pseudo first- and second-order models, intraparticle diffusion and Bangham's models. The equilibrium data were simulated using Langmuir, Freundlich, Dubinin and Radushkevich (D-R) and Temkin isotherms. The results reveal that the pseudo second-order model and Langmuir isotherm fit the kinetics and equilibrium data, respectively. The adsorption capacity of BPA on the surface of CNTs fluctuates very little with pH in the range of 3-9, suggesting the high stability of CNTs as an adsorbent for BPA over a rather wide pH range. The values of ΔH0 and ΔS0 were calculated to be − 11.7 kJ/mol and 46.1 J/mol, respectively. The isotherm and thermodynamic simulations indicate that the adsorption of BPA onto as-grown CNTs proceeds by physisorption process. 相似文献
11.
Cheng-Li Lin 《Electrochimica acta》2004,49(4):573-580
Sol-gel films prepared from quaternary amine functionalized silicon alkoxide precursor on electrode surfaces have been investigated as anion-exchange and permselective coatings for electroanalytical investigations. These modified electrodes were evaluated with Fe(CN)63− and Ru(bpy)32+ as the analytes using cyclic voltammetry. At low solution pH, the anionic analyte preconcentrated within the functionalized sol-gel coating and resulted in an improvement in detection limit of about 2 orders of magnitude compared to bare electrodes, but the response for the cationic analyte was suppressed. The modified electrodes are rugged and reproducible and can be regenerated. We have also shown that the anion-exchange and permselective properties of the modified electrodes can be affected by the composition, concentration, and pH of the support electrolyte. 相似文献
12.
Novel glassy carbon modified electrodes were functionalised with tetra-n-butylammonium (TBA) hybrid salts of several α-Keggin-type polyoxosilicotungstate anions. The salts were immobilized via a one-step deposition of micrometer thick coatings by the droplet evaporation method. The polyanion salts included the lacunary anion compound [(C4H9)4N]4H4[SiW11O39], and the metal-substituted derivatives [(C4H9)4N]4H[SiW11FeIII(H2O)O39] and [(C4H9)4N]4H2[SiW11CoII(H2O)O39]·H2O. The chemically modified electrodes were medium term stable and their preparation was quite reproducible and easy to perform. The morphology of the deposits was evaluated by optical microscopy and by scanning electron microscopy.The electrochemical features of the immobilized polyanion salts were to some extent different from those of the corresponding soluble species, namely in what concerns peak potential values and the effect of the substituting transition metal on the tungsten processes. Additionally, for all immobilized polyanion salts, the effect of the scan rate and of pH on the voltammetric features of the first W reduction process allowed to conclude that this process was diffusion controlled and accompanied by uptake of protons. The iron monosubstituted TBA modified electrode retained the mediation properties towards the reduction of nitrite found for the corresponding soluble polyoxoanion. 相似文献
13.
《Diamond and Related Materials》2005,14(2):213-219
Boron-doped, undoped and nitrogen-doped diamond films were synthesized by microwave plasma assisted chemical vapor deposition (MP-CVD). Raman spectroscopy, XPS, EPMA and UV–Vis were used to characterize the properties of the synthesized films. Electrochemical characteristics for several redox systems on the three kinds of diamond films were examined. For Li+/Li (E0=−3.05 V) and H+/H2 (E0=0.00 V) redox couples, the marked differences in cyclic voltammetric (CV) behaviors were observed on the nitrogen-doped diamond films, whereas for Fe(CN)3−/4− (E0=0.36), Au/AuCl4− (E0=1.00) and O2/H2O (E0=1.23 V) couples, the CV behaviors on the nitrogen-doped films were similar to those on the boron-doped or undoped diamond films. The significant differences of CV behaviors could be explained by hypothesizing that the electron transfers of the redox species in the solution on diamond electrodes happened at the top of valence band together with the surface doping model suggested by F. Maier and colleagues [F. Maier, M. Riedel, B. Mantel, J. Ristein, L. Ley, Phys. Rev. Lett. 85 (2000) 3472]. 相似文献
14.
Zhiqiang Liang Ruojun Lao Jing Wang Yongbiao Liu Lihua Wang Qing Huang Shiping Song Genxi Li Chunhai Fan 《International journal of molecular sciences》2007,8(7):705-713
Carbon nanotubes (CNTs) can be effectively dispersed and functionalized by wrapping with long single-stranded DNA (ssDNA) synthesized by asymmetric PCR. The ssDNA-CNTs attached on surface of glass carbon electrode made it possible for electrochemical analysis and sensing, which was demonstrated by reduction of H2O2 on hemoglobin/ssDNA-CNTs modified electrodes. This research showed the potential application of DNA-functionalised CNTs in construction of future electrochemical biosensors. 相似文献
15.
Pure and mixed N-hydroxysuccinimide-terminated and butanethiol monolayers were prepared on flat gold (1 1 1) surfaces with the intent of developing suitable platforms for the direct biomolecules immobilisation. The self-assembled monolayers (SAMs) were characterised by electrochemical reductive desorption of the thiolate from the gold surface. The data have shown that certain solution proportions of the two compounds yield modified electrodes exhibiting intermediate electrochemical behaviour of the corresponding pure SAMs. The reactivity of the terminal N-hydroxysuccinimide (NHS) towards amine functionalities has been tested for the covalent attachment of Dopamine. The cyclic voltammetric responses of the investigated monolayers, after contacting with a Dopamine solution, have confirmed the chemical coupling of the amine as well as the formation of mixed SAMs. The Dopamine surface coverage increased with the amount of surface NHS. Laccase was also successfully immobilised onto this modified electrodes. The electrochemical behaviour of the modified SAMs with Laccase indicates direct electron transfer between the immobilised enzyme and the gold surface. Evidence for Laccase immobilisation was also provided by atomic force microscopic measurements. 相似文献
16.
Ali Ye?ilda? 《Electrochimica acta》2010,55(23):7000-7009
In this study, pyridine, quinoline and phenanthroline molecules were covalently bonded to glassy carbon (GC) electrode surfaces for the first time using the diazonium modification method. Then, the complexation ability of the modified films with ruthenium metal cations was investigated. The derivatization of GC surfaces with heteroaromatic molecules was achieved by electrochemical reduction of the corresponding in situ generated diazonium salts. X-ray photoelectron spectroscopy (XPS) was used to confirm the attachment of heteroaromatic molecules to the GC surfaces and to determine the surface concentration of the films. The barrier properties of the modified GC electrodes were studied in the presence of redox probes such as Fe(CN)63− and Ru(NH3)63+ by cyclic voltammetry. Additionally, the presence of the resulting organometallic films on the surfaces was verified by XPS after the chemical transformation of the characterized ligand films to the ruthenium complex films. The electrochemical behavior of these films in acetonitrile solution was investigated using voltammetric methods, and the surface coverage of the organometallic films was determined from the reversible metal-based Ru(II)/Ru(III) oxidation waves. 相似文献
17.
Conducting polypyrrole (PPy) thin-film electrodes were prepared by the electropolymerization of pyrrole on gold-coated glass plates. Films of various roughnesses were obtained by the variation of the scan rates during electropolymerization. These thin films were modified by doping with 6mM of the dopant NiCl2. The surface morphology of the films was studied by scanning electron microscopy and atomic force microscopy (AFM), which suggested films prepared with a high scan rate were rougher in nature than the films produced with a low scan rate. The electrocatalytic reduction of nitrobenzene was carried out with these electrodes with the cyclic voltammetry technique in acetonitrile containing 0.1M HClO4 as a supporting electrolyte. The various results obtained show that the conducting PPy thin-film electrodes were catalytically active toward the electroreduction process. The modified PPy film electrodes doped with NiCl2 were more active toward nitrobenzene electroreduction than the PPy film alone. The results indicate that the roughness of the films played a very important role in determining their catalytic activity. The PPy films that were more rough in nature were catalytically more active than the smooth films; this may have been due to the availability of more reactive sites in the case of rough films. The apparent diffusion coefficients of the PPy film electrodes were also calculated. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
18.
Wenjing Shan 《Electrochimica acta》2005,51(3):432-440
Protein-Pluronic film modified electrodes were constructed by casting the mixture of hemoglobin (Hb) or myoglobin (Mb) and triblock copolymer poly(ethylene oxide)100-poly(propylene oxide)65-poly(ethylene oxide)100 (Pluronic) solutions onto the surface of pyrolytic graphite (PG) electrodes. A pair of well-defined and nearly reversible CV peaks at about −0.35 V versus SCE in pH 7.0 buffers was observed for protein-Pluronic films, characteristic of the protein heme Fe(III)/Fe(II) redox couples. The films were characterized by scanning electron microscopy (SEM), UV-vis and IR spectroscopy, as well as electrochemistry. The heme proteins were quite stable and retained their near-native structure in Pluronic films. Oxygen, hydrogen peroxide, nitrite and nitric oxide were electrochemically catalyzed by protein-Pluronic films with significant lowering of reduction overpotential. Both nitrite and hydrogen peroxide underwent dismutation in electrocatalysis. The reduction of NO2− and H2O2 on protein-Pluronic films was actually the catalytic reduction of their disproportionation products, NO and O2, respectively. The biocatalytic mechanism of these substrates at protein-Pluronic film electrodes were discussed and speculated. 相似文献
19.
Qing Lin Sheng 《Electrochimica acta》2007,52(13):4506-4512
The electrochemical properties of an electroactive rare earth metal hexacyanoferrate, neodymium hexacyanoferrate (NdHCF) were studied by mechanically attaching NdHCF samples to the surface of carbon ceramic electrodes (CCEs) derived from sol-gel technique. The resulting modified electrodes exhibit well-defined redox responses with the formal potential of 0.241 V (versus SCE) at a scan rate of 20 mV s−1 in 0.5 M KCl solution. The voltammetric characteristics of the NdHCF-modified CCEs in the presence of different alkali metal cations (Li+, Na+, K+, Rb+ and Cs+) were investigated by voltammetry. The NdHCF-modified CCEs presented a good electrocatalytic activity towards the reduction of hydrogen peroxide (H2O2), and was used for amperometric detection of H2O2. In addition, the NdHCF-CCEs exhibited a distinct advantage of simple preparation, surface renewal, good stability and reproducibility. 相似文献
20.
Streptavidin (SAv) has been modified by covalent coupling of ferrocene (Fc) electron-relay groups to lysine-residues of the protein backbone. Reagent ratios were varied to obtain conjugates with three to 16 Fc groups per SAv. Biotin was covalently attached to gold electrodes for the anchoring of the conjugate monolayers. A method was devised to produce in situ bisbiotin functionalities that efficiently cross-linked Fc16SAv to form multilayer electrode coatings. The electrochemical charge transport properties of the coatings were examined by cyclic voltammetry. The characteristic current density iE measuring the rate of charge transport was 1 mA cm−2 for one monolayer of Fc16SAv. It was found that the transport of electrochemical charge through the Fc-containing SAv system is a diffusion-like process, as evidenced by the proportionality of the peak current and the square root of sufficiently high scan rate, and the inverse dependence of iE on the number (thickness) of Fc16SAv layers. 相似文献