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ABSTRACT: The electrochemical properties of electrodes modified with metal/metal oxides depend not only on the nature of the materials but also on the composition and substrate as well. In this study, dendritic CuNi nanostructured materials with a distinguishable bimetal phase were achieved by electrodeposition in 0.05 M Na2SO4 solution containing 0.05 M CuSO4 and 0.05 M NiCl2 at −1.0 V on the surface of titanate thin films, which were self-assembled from the titanate nanaosheets exfoliated by n-propylamine. The structures, morphologies, and elemental molar ratio of the titanate-supported CuNi were analyzed by XRD, SEM, and ICP-AES, respectively. The electrochemical activities of the CuNi nanostructured electrodes toward glucose oxidation were evaluated, and factors that affect the electrocatalytic activities of the electrodes were examined and optimized. The potential applications of the CuNi nanostructured films for fabrication of enzymeless glucose sensors were also investigated. The assay performances of the sensor evaluated by conventional electrochemical techniques revealed a quick response, good reproducibility, and enhanced sensitivity in glucose determination compared with that of pure Cu or Ni electrodeposited on the self-assembled titanate template.
11/2010;
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ABSTRACT: Copper oxide nanofibers (CuO-NFs) prepared by electrospinning and subsequent thermal treatment processes were demonstrated for the first time for glucose non-enzymatic determination. The structures and morphologies of CuO-NFs were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction spectrum (XRD). Different dispersants were utilized for the suspension preparation and effects of ultrasonic time on the films electrode fabrication were investigated in detail. The assay performances to glucose were evaluated by cyclic voltammetry (CV) and chronoamperometry (I-t). Results revealed a high sensitivity (431.3 microAmM(-1)cm(-2)), fast response (about 1s), long-term stability and excellent resistance towards electrode fouling in the glucose determination at +0.40V. The improved performances of CuO-NFs films electrode for electro-oxidation glucose were ascribed to the high surface-to-volume ratio, complex pore structure, extremely long length of the as-prepared CuO-NFs, and the excellent three-dimensional network structure after immobilization. Results in this study suggest that electrospun CuO-NFs is a promising 1-D nanomaterial for further design and microfabrication of bioelectrochemical nanodevices for glucose determination.
Biosensors & bioelectronics 09/2009; 25(4):708-14. · 5.43 Impact Factor
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ABSTRACT: This work demonstrated for the first time the feasibility of electrochemical preparation of copper-based/titanate intercalation electrode material. Cupric ion was first intercalated into the layered titanate host by ion exchange and subsequently reduced by electrochemical methods, resulting in the copper-based/titanate intercalation electrode materials. The successful formation of copper-based/titanate (Cu−TO) intercalation materials by electrochemical reduction following ion exchange (Cu(II)−TO) were characterized by X-ray diffraction, scanning electron microscopy, and conventional electrochemical techniques. The effects of experimental conditions, i.e., dispersant for ion exchange, electroreductive medium, and methods, on activities of the resulting electrode materials toward glucose electrooxidition were investigated in detail. Results revealed that both the stability and the electrooxidative activity to glucose of Cu−TO intercalation electrode materials were largely improved compared with that of Cu(II)−TO, indicating the necessity and superiority of the electrochemical reduction step carried out following ion exchange. The potential applications of this new class of copper-based/titanate materials in electrocatalysis and electroanalysis were demonstrated. Present study provides a low cost and simply controlled test-bed for fundamental study on electrochemical preparation of a new class of metallic/metal-based titanate intercalation materials for electrocatalysis, electroanalysis, and relevant fields.
04/2009;
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ABSTRACT: Copper-based titanate intercalation electrode materials (referred as Cu-TO) were achieved by electrochemical reduction of the intercalated cupric ions that were ion exchanged on the layer structured titanate films by using n-propylamine as an exfoliating agent. The copper-based titanate intercalation electrode materials were characterized by X-ray diffraction (XRD), electrochemical techniques and inductive coupled plasma-atomic emission spectroscopy (ICP-AES). These copper-based titanate materials were exploited to fabricate the enzymeless glucose sensors, and their assay performances to glucose were evaluated by conventional electrochemical techniques. Cyclic voltammetry (CV) and chronoamperometry (I-t) revealed a high sensitivity, fast response, excellent stability, and good reproducibility in the glucose determination at +0.55 V. Under optimal conditions, the electrocatalytic response of the sensor was proportional to the glucose concentration in the range of 2.5x10(-7) M to 8.0x10(-3) M with a detection limit of 5.0x10(-8) M (signal-to-noise=3). Moreover, the intercalated copper electrode materials exhibited high stability and improved selectivity for glucose compared with the more apparently accessible copper. This work also provides a simply controlled test-bed for electrochemical functionalization of layered titanate for sensor applications.
Biosensors & bioelectronics 01/2009; 24(8):2404-9. · 5.43 Impact Factor
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ABSTRACT: Copper nanoparticles (CuNPs) encapsulated by polymeric stabilizer of polyvinylpyrrolidone (PVP) (noted as PVP-CuNPs) were simply prepared and used to construct an enzymeless glucose sensor on a solid substrate. Sensing and assay performance of the CuNPs-based sensor to glucose were evaluated in detail. Cyclic voltammetry (CV), chronoamperometry (I–t) and flow injection amperometry (FIA) revealed a high sensitivity, excellent stability, and good reproducibility in the glucose determination at +0.45 V, which was 200 mV more negative than those in former reports. A detection limit as low as 1.0×10−8 M (signal-to-noise=3) and a linear range of 1.0×10−7 M to 5.0×10−3 M were obtained in this study.
Electroanalysis 08/2006; 18(21):2055 - 2060. · 2.87 Impact Factor
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ABSTRACT: A stable monolayer of the inorganic-organic hybrid polyoxometalate (Bu4N)2Mo6O19, denoted as Mo6O19, was formed on a sodium-3-mercapto-1-propanesulfonate (MPPS)-covered gold electrode surface, interlaced with an anionic poly(dimethyldiallylammonium chloride) (PDDA) binding layer based on the electrostatic self-assembled (ESA) technique. Electrochemical characterization of the Mo6O19 self-assembled thin films on the solid surface by cyclic voltammetry and AC impedance spectroscopy revealed a stable and sensitive electrocatalytic response to the reduction of iodate. Iodate was determined amperometrically through a flow injection cell at the modified electrode in the concentration range of 1.0 x 10(-6) to 1.0 x 10(-1) M with a detection limit of 8 x 10(-8) M (signal-to-noise ratio = 3). Performance was improved to meet practical needs compared with previously reported analogues.
Analytical and Bioanalytical Chemistry 07/2005; 382(4):1187-95. · 3.78 Impact Factor
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ABSTRACT: The electrochemical characteristics of various kinds of multilayers of gold nanoclusters (GNCs) were investigated. Two types of gold nanoclusters, one covered by self-assembled monolayers (SAMs) of mercaptoundecanoic acid (MUA), hexanethiol (C6SH), and ferrocenylhexanethiol (FcC6SH), MHF-GNC, and the other with MUA and C6SH, MH-GNC, were used. The multilayers were constructed on a Au(111) surface based on a carboxylate/metal cation (Cu++)/carboxylate or carboxylate/cationic polymer (poly(allylamine hydrochloride):PAH)/carboxylate electrostatic interaction. While the multilayers constructed by the former method were stable only in nonaqueous solutions, those constructed by the latter method were stable even in aqueous solutions. Electrochemical measurements of the multilayers of MHF-GNCs showed a pair of waves corresponding to the redox of the ferrocene group around 350-480 mV and the charge of these peaks, i.e., the amount of adsorbed GNC, increased linearly with the construction cycle up to 6 cycles in the former and to 18 cycles in the latter. A rather reversible redox response of the ferrocene moiety was observed even at the gold electrodes with five GNC layers of two different sequences in which MHF-GNC exists as the layer closest to the gold electrode, ie., the first layer, or as the outermost layer with MH-GNC in the other layers. These results show the facile transfer of electrons and ions through the multilayers of the SAM-covered GNCs and electron transfer between the ferrocene moiety and the Au(111) electrode takes place through the GNC cores by hopping.
Faraday Discussions 02/2002; · 5.00 Impact Factor
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ABSTRACT: A novel vanadium oxide polypropylene carbonate modified glassy carbon electrode was developed and used for the measurement of ascorbic acid (AA). The electrode was prepared by casting a mixture of vanadium tri(isopropoxide) oxide (VO(OC3H7)3) and poly(propylene carbonate) (PPC) onto the surface of a glassy carbon electrode. The electrochemical behavior of the VO(OC3H7)3–PPC film modified glassy carbon electrode was investigated by cyclic voltammetry and amperometry. This modified electrode exhibited electrocatalytic response to the oxidation of ascorbic acid. Compared with a bare glassy carbon electrode, the modified electrode exhibits a 220 mV shift of the oxidation potential of ascorbic acid in the cathodic direction and a marked enhancement of the current response. The response current revealed a good linear relationship with the concentration of ascorbic acid in the range of 4 × 10−8 and 1 × 10−4 mol L−1 and the detection limit of 1.5 × 10−8 mol L−1 (S/N = 3) in the pH 8.06 Britton–Robinson solution. Quantitative recovery of the ascorbic acid in synthetic samples has been obtained and the interferences from different species have been studied. The method has been successfully applied to the determination of ascorbic acid in fruits. The concentrations of ascorbic acid measured by this method are in good agreement with the literature value. It is much promising for the modified films to be used as an electrochemical sensor for the detection of ascorbic acid.
Sensors and Actuators B: Chemical.
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ABSTRACT: A novel chemically-modified electrode containing 12-molybdophosphoric acid was achieved on the surface of platinum electrode by sol-gel technique. The electrochemical behavior of the modified electrode was characterized by cyclic voltammetry in detail. The film electrode obtained was very stable and exhibited electrocatalytic response for reduction of bromate, chlorate and hydrogen peroxide. Hydrogen peroxide was determined amperometrically at the modified electrode in the concentration range of 3×10−2 to 2×10−5M and a detection limit of 7×10−6M (signal-to-noise ratio 3).
Electrochimica Acta.
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ABSTRACT: Amounts of gold nanoclusters (GNCs) in multilayer assembly with polymer binding layers has been demonstrated to be controlled by pH and ionic strength of the polymer solution when GNCs covered with mercaptoundecanoic acid (MUA) were assembled on a solid substrate in a layer-by-layer (LBL) fashion utilizing terminal carboxylate groups as charged sites to electrostatically bind to protonated amine groups of poly(allylamine hydrochloride) (PAH), which was used as a binding layer. Formation of these GNC multilayers was followed by monitoring the electrochemical response of the ferrocene moiety attached to the GNC core, which acted as a redox probe. The apparent acid dissociation constant of MUA on the GNC surface estimated from correlation between the amount of adsorbed GNCs and pH of the PAH solutions was in good agreement with those previously reported. Facile charge transport within LBL multilayer assemblies formed under various pH and/or ionic strengths of polymer solution revealed an open porous film microstructure contributing to facile charge transfer by hopping through GNC sites as well as with the aid of electrolyte in pores in such architectures. This study provides significant fundamental basis for construction of highly charged complex structures containing redox groups and useful applications in catalysis and devices fabrication based on charge transfer.
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ABSTRACT: Two types of gold nanoclusters (GNCs), one covered by self-assembled monolayers of mercaptoundecanoic acid (MUA), hexanethiol (C6SH), and ferrocenylhexanethiol (FcC6SH), MHF-GNC, and the other with MUA and C6SH, MH-GNC, were used for the construction of ten GNC layers of two different sequences on an MUA modified Au(1 1 1) surface based on the carboxylate/polycation (poly(allylamine hydrochloride), PAH)/carboxylate electrostatic interaction. MHF-GNC was placed either as the layer closest to the gold electrode, i.e. the first layer, or as the outermost layer with MH-GHC in the other layers. A quasi-reversible redox peak with a constant charge corresponding to the redox reaction of the ferrocene moiety of the MHF-GNC monolayer was observed at both electrodes, showing electrons and perchlorate ions could be transferred through the MH-GNC/PAH multilayers. Cross-sectional transmission electron microscopy (TEM) revealed that the size of the immobilized GNC was almost same as that in solution and well-separated GNCs were dispersed rather uniformly within the polymeric matrix. The incorporation of perchlorate ion upon the oxidation of the ferrocene moiety of the MHF-GNC was demonstrated by electrochemical quartz crystal microbalance measurement. Based on the above results, the charge transfer mechanism in the GNC multilayers was discussed.
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ABSTRACT: A novel supramolecular complex of octamolybdates and cyclodextrin was simply prepared for the first time by self-assembled method under room temperature. Successful formation of the functional material was demonstrated by carrying out analysis on its thin films supported on the gold surface by various electrochemical techniques, based on the redox probe of octamolybdates contained in the assembly. Sensing and assay performance of the final functional films were evaluated in FIA system by determining oxo anions in samples based on the electroactivity of surface-confined molybdenum catalyst.
Sensors and Actuators B: Chemical.
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ABSTRACT: Novel sol–gel glass thin films containing 12-molybdophosphoric acid were achieved on the surface of a glassy carbon electrode by the sol–gel technique. The electrochemical behavior of the modified electrode was studied in detail. The new chemically modified electrode was shown to exhibit a high electrocatalytic response for the reduction of iodate. Iodate in table salt was determined amperometrically in pH 2.6 acidic aqueous solution at the modified electrode with satisfactory results. The method had a linear range from 5×10−6 to 6×10−3 M and a detection limit of 1×10−6 M (signal-to-noise ratio 3).
Analytica Chimica Acta.
