An amperometric sensor for hydrazine based on nano-copper oxide modified electrode
ABSTRACT A sensitive hydrazine sensor has been fabricated using copper oxide nanoparticles modified glassy carbon electrode (GCE) to
form nano-copper oxide/GCE. The nano-copper oxide was electrodeposited on the surface of GCE in CuCl2 solution at −0.4V and was characterized by Scanning electron microscopy and X-ray diffraction. The prepared modified electrode
showed a good electrocatalytic activity toward oxidation of hydrazine. The electrochemical behavior of hydrazine on nano-copper
oxide/GCE was explored. The oxidative current increased linearly with improving concentration of hydrazine on nano-copper
oxide/GCE from 0.1 to 600μM and detection limit for hydrazine was evaluated to be 0.03μM at a signal-to-noise ratio of 3.
The oxidation mechanism of hydrazine on the nano-copper oxide/GCE was also discussed. The fabricated sensor could be used
to determine hydrazine in real water.
KeywordsAmperometric sensor–Nano-copper oxide–Hydrazine–Electrodeposition
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ABSTRACT: Cu2O is an efficient catalyst in the partial oxidation of propylene to acrolein, while propylene oxidation on CuO leads to complete combustion. The interaction of propylene at elevated temperature (>300 K) and elevated pressure (5 Torr) with cuprous and cupric oxide has been investigated with core level XPS, resonant photoemission, and temperature-programmed desorption. Reduction of the copper oxide surfaces was examined as a function of temperature and revealed that cupric oxide has a greater reactivity toward propylene oxidation than cuprous oxide (Ea = 5.9 versus 11.5 kcal/mol for cuprous oxide (24.7 and 48.1 kJ/mol)). This variable temperature oxidation of propylene was also monitored via core level and resonant photoemission and was found to occur by a similar mechanism on both surfaces. Reaction at lower temperature produces a surface intermediate which exhibits carbon 1s XPS peaks at 284.0 and 285.5 eV binding energy in a 2:1 intensity ratio. This is consistent with an allyl alkoxide surface species, indicating a reaction mechanism involving an initial H atom abstraction from propylene followed by rapid oxide insertion. The relative surface reactivities are related to the redox potential of the metal ion and the pKa of the protonated surface oxide. The presence of a significant amount of this surface alkoxide is consistent with a relatively slow alkoxide decomposition step. This decomposition occurs more readily on the cuprous oxide surface (Ea (decomposition) = 24.5 kcal/mol (102.6 kJ/mol) versus 28.7 kcal/mol (120.1 kJ/mol) on cupric oxide) and involves a hydride elimination mechanism. At elevated temperatures a new carbon 1s peak at 288 eV binding energy is observed which is consistent with the formation of further oxidized surface species (RCOx). The CuO surface is found to be more reactive in forming these nonselective highly oxidized products. The observed differences in reactivity, rates of reaction steps, selectivity, and product distribution are addressed and provide insight into the factors which influence the reactivity and selectivity of the copper oxides toward the heterogeneous oxidation of propylene.Journal of The American Chemical Society - J AM CHEM SOC. 10/1998; 120(44).
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ABSTRACT: CuO nanowires have been prepared and applied for the fabrication of glucose sensors with highly enhanced sensitivity. Cu(OH)(2) nanowires were initially synthesised by a simple and fast procedure, CuO nanowires were then formed simply by removing the water through heat treatment. The structures and morphologies of Cu(OH)(2) and CuO nanowires were characterised by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The direct electrocatalytic oxidation of glucose in alkaline medium at CuO nanowire modified electrodes has been investigated in detail. Compared to a bare Cu electrode, a substantial decrease in the overvoltage of the glucose oxidation was observed at the CuO nanowire electrodes with oxidation starting at ca. 0.10 V vs. Ag/AgCl (saturated KCl). At an applied potential of 0.33 V, CuO nanowire electrodes produce high and reproducible sensitivity to glucose with 0.49 microA/micromol dm(-3). Linear responses were obtained over a concentration range from 0.40 micromol dm(-3) to 2.0 mmol dm(-3) with a detection limit of 49 nmol dm(-3) (S/N = 3). The CuO nanowire modified electrode allows highly sensitive, low working potential, stable, and fast amperometric sensing of glucose, thus is promising for the future development of non-enzymatic glucose sensors.The Analyst 02/2008; 133(1):126-32. · 3.97 Impact Factor
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ABSTRACT: This article reports on the novel mixed cobalt and copper hexacyanoferrate (CoCuHCF)-modified carbon fiber cylinder microelectrode (CFCME) and its application to potentiometric determination of highly toxic hydrazine. The substrate CFCMEs were fabricated in a standard manner using carbon fibers of 7 µm in diameter. The CoCuHCF film was deposited electrochemically by cycling the potential between 0 and +1.0 V (vs. Ag/AgCl) in a solution containing the precursor salts. It exhibited good chemical stability in the pH range from 1 to 9. The effects of the coverage/thickness of the CoCuHCF coating, of the pH of a measurement solution, and of the activation of the sensor, on the potentiometric response to hydrazine were examined in detail. The potentiometric behavior of CoCuHCF film in the presence of hydrazine, with the potential (emf) slope of –55 mV/decade, was compared with those of four single metal HCF films (CoHCF, CuHCF, FeHCF, and NiHCF) prepared in the same way, and the possible role of the CoCuHCF film components is explored and discussed. The emf versus log CHyd calibration plot was linear over 3 orders of magnitude, from 1.0×10–6 to 1.0×10–3 mol/L, with a correlation coefficient of 0.995. The limit of detection was found to be 5×10–7 mol/L. The response times of 10 to 30 s and the temperature coefficients of ca–2.7 mV/°C were obtained at various hydrazine concentrations. The repeatability of measurements was very good with the relative standard deviation ranging from 3 to 4% (n=10), depending on hydrazine concentration. The selectivity of the reported microsensor was found excellent, except in the case of a few negatively charged interferents for which it was greately improved by an additional Nafion coating. The useful lifetime of the all-solid microsensor was found to be more than 2 months when stored in air.Electroanalysis 01/2000; 12(1):48 - 54. · 2.82 Impact Factor