Cross-sensitivity electrodes

Ciosek, P., Augustyniak, E., and Wroblewski, W. (2004a). Polymeric membrane ion-selective and cross-sensitive electrode-based electronic tongue for qualitative analysis of beverages. Analyst 129(7), 639-644. 

Two types of potentiometric electrodes are usually described, the ISE, which was developed to selectively recognize ions and used to analyze ions (anions or cations) in a solution and the cross-sensitivity electrodes (CSE), used in sensor arrays for solution analysis, which due to their low selectivity gives, as output, a matrix fingerprint. E-tongue systems (multisensor systems with several low-selective sensors) are an example of this application. 

Legin AV, Vlasov YG, Rudnitskaya AM, Bychkov EA (1996) Cross-sensitivity of chalcogenide glass sensors in solutions of heavy metal ions. Sens Actuators B 34 456 61 De Marco R, Shackleton J (1999) Cahbration of the Hg chalcogenide glass membrane ion-selective electrode in seawater media. Talanta 49 385-391... 

It is also essential to know the cross-sensitivity of the zirconia single-crystal sensors to other gases. Sensors with porous Pt electrodes are known to be sensitive to gases such as CO at low temperatures [41], and in fact, this cross-sensitivity has been proposed as a principle for carbon monoxide sensors at low temperatures by some researchers [42, 43]. This effect is attributed to the ability of CO to compete successfully with oxygen for adsorption sites on Pt at temperatures from 500°C to 650°C. It was observed that the zirconia single-crystal sensor with thin-film Pt-Zr02-Y2O3 electrodes is less sensitive to CO than similar polycrystalhne sensors with porous Pt electrodes, but small em/errors still occur at 300-360°C. 

FIGURE 5.14 Cross-sensitivities to various gases, such as CO, CjHg, NO, and NO2 (400 ppm each), at 800°C in humid conditions for the sensor attached with a 10 wt % CuO-added synthesized NiO-SE. (From Plashnitsa, V.V., Ueda, T., and Miura, N., Improvement of NOj sensing performances by an additional second component to the nano-structured NiO sensing electrode of YSZ-based mixed-potential-type sensor, Int. J. Appl. Ceram. Tech. 3 (2006) 127-133. With permission.)... 

Soft drinks Eight cross-sensitive polymeric membranes on a screen-printed carbon paste electrode... 

The cross-sensitivity to other gases has been employed to construct amperometric sensors for those species. Commonly used, for example, are sensors for dissolved chlorine (e.g., in swimming pools), which are very similar in construction to Clark electrodes for oxygen. 

It is to be expected that other types of surfactant-sensitive electrodes can be used with equal or greater success, and it would not be surprising if the two-phase methods, e.g. that of Cross (section 7.1.3) could also be used, although the author is unaware of any published evidence. 

Fig. 9.6 (a) Schematic view of YSZ-based device structure with metal oxide sensing electrodes tmd (b) cross-sensitivities to various gases at 600 °C for the YSZ-based device using CdO and SnOj electrodes. (Gas concentration CO, Hj, NO, NOj, CH 200 ppm each, CO 10,(X)0 ppm, H O 1.5 kPa) (Reprinted with permission from Miura and Yamazoe (1998). Copyrights 1998 Elsevier)... 

A D-glucose-sensitive electrode has been constructed by coating of a platinum electpode with a cross-linked poly(vinylalcohol) layer containing immobilised D-glucose oxidase and ferrocene. ... 

Such sensors show long-term stability without cross sensitivity vs. water vapour. Organic compounds are oxidised by oxygen on the surface of hot electrodes. 

Figure 10.17. (a) Schematic diagram of the nanowire dye-sensitized solar cell. Light is incident through the bottom electrode, (b) SEM cross section of a solution-fabricated ZnO nanowire array on fluorine-doped tin oxide. The wires are in direct contact with the substrate. Scale bar, 5 pm. Reproduced from Ref. 41, Copyright 2005, with permission from the Nature Publishing Group. 

A cross-sectional schematic of a monolithic gas sensor system featuring a microhotplate is shown in Fig. 2.2. Its fabrication relies on an industrial CMOS-process with subsequent micromachining steps. Diverse thin-film layers, which can be used for electrical insulation and passivation, are available in the CMOS-process. They are denoted dielectric layers and include several silicon-oxide layers such as the thermal field oxide, the contact oxide and the intermetal oxide as well as a silicon-nitride layer that serves as passivation. All these materials exhibit a characteristically low thermal conductivity, so that a membrane, which consists of only the dielectric layers, provides excellent thermal insulation between the bulk-silicon chip and a heated area. The heated area features a resistive heater, a temperature sensor, and the electrodes that contact the deposited sensitive metal oxide. An additional temperature sensor is integrated close to the circuitry on the bulk chip to monitor the overall chip temperature. The membrane is released by etching away the silicon underneath the dielectric layers. Depending on the micromachining procedure, it is possible to leave a silicon island underneath the heated area. Such an island can serve as a heat spreader and also mechanically stabihzes the membrane. The fabrication process will be explained in more detail in Chap 4. 

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