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p. 41-49
Received: 7 January 2002 / Accepted: 21 January 2002 / Published: 4 February 2002
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| Download PDF Full-text (416 KB) Abstract: L-Cysteine is combined onto gold electrode to form a self-assembled monolayers modified electrode (L-Cys/Au SAMs) by taking advantage of strong sulfur-gold interaction. ATR-FTIR, SEM, cyclic voltammetry (CV) and impedance were used for the characterization of the film. It shows excellent stability upon voltametric scanning and a good voltametric response towards hydroquinone with the potential ranged from 0.8 to –0.2 V (vs.SCE) in 0.5M HAc-NaAc buffer solution (pH 4.8). The oxidation potential of hydroquinone on the modified electrode shifted negatively about 330 mV as compared with the bare gold electrode. The plot of catalytic current vs.its concentration has a good linear relation in the range of 2.0×10-6 ~2.0×10-4 M with the correlation coefficient of 0.9986 and the detection limit of 4.0×10-7 M by different pulse voltammetry (DPV). Mechanism for the electrocatalytical process has been studied.
p. 50-61
Received: 6 February 2002 / Accepted: 8 February 2002 / Published: 22 February 2002
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| Download PDF Full-text (322 KB) Abstract: A ceramic thick film humidity sensor, produced from MnZn ferrite, is presented. The proposed sensing mechanism is a combination of proton hopping, hydronium diffusion, and vacancy donor traps releasing electrons into the conduction band. The sensor structure comprises a two-layer device; the first layer is an interdigitated conductor and the second layer is a 30μm thick sensing layer. The effects of sintering the sensing pastes in air and vacuum have been reported. The air-fired sample exhibits the highest humidity sensitivity (1.54%/RH%) and the lowest temperature sensitivity (0.37%/o C). The vacuum-fired sample has the lowest humidity sensitivity (0.043%/RH) and the highest temperature sensitivity (0.77%/o C). The sensitivity results indicate that the air-fired sample has the best potential for use in humidity sensing applications.
p. 62-70
Received: 9 January 2001 / Accepted: 15 February 2002 / Published: 23 February 2002
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| Download PDF Full-text (138 KB) Abstract: Two metals are used in resonant layers for chemical sensors based on surface plasmon resonance (SPR) - gold and silver. Gold displays higher shift of the resonance angle to changes of ambient refraction index and is chemically stable. Silver posses narrower resonance curve thus providing a higher signal/noise ratio of SPR chemical sensors, but has a poor chemical stability. A new structure of resonant metallic film based on bimetallic silver/gold layers (gold as an outer layer) is suggested. It combines advantages of both gold and silver resonant layers. Bimetallic resonant films display so high shift of resonance angle on changes of ambient refraction index as gold films, but show narrower resonance curve, thus providing a higher signal / noise ratio. Additionally, the outer gold layer protects silver against oxidation.
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