Sensing electrode fabrication

The schematic diagram of a gas-sensing electrode is illustrated in Figure 16.8, that comprises of essentially a reference electrode (E), a specific-ion electrode (B), and an internal electrolyte solution (F) contained in a cylindrical plastic tube (G). One end of the plastic tubing is provided with a thin, replaceable, gas-permeable membrane that separates the internal electrolyte solution from the external solution containing gaseous analyte. However, the exact composition and specifications of this gas-permeable membrane is usually described by its respective manufacturers. It is normally made up of a thin microporous film fabricated from a hydrophobic plastic material. 

The membrane and electrode assembly used for the detection of oxides of nitrogen is similar to that used for CO detection, except that the sensing electrode is fabricated from a graphite Teflon mix. 

S. Hashioka, M. Saito, E. Tamiya and H. Matsumura, Deoxyribonucleic acid sensing device with 40-nm-gap-electrodes fabricated by low-cost conventional techniques, Appl. Phy. Lett., 85 (2004) 687-688. 

Therefore, the primary electrode reaction includes the sensed species. Such electrodes give a direct response according to the Nemst equation for the logarithm of the activity of the species. The details of electrode fabrication and their characteristics are discussed in Chapter 5. An extensive authoritative treatment is provided by Ives and Janz.19... 

White et al. synthesized nanometric La2Cu04 through three techniques auto-ignition, Pechini method, and coprecipitation (White et al., 2008). The NPs were used to fabricate sensing electrodes for NO, and the effect of electrode microstructure on the sensitivity and response time was studied. The response times of the sensors were exponentially dependent on electrode grain size. Sensors with fine-grained electrodes were able to produce a steady-state and consistent voltage at lower temperatures, which improved their response sensitivity. 

The equilibration between the two electrolytes can sometimes require an additional phase, some specific examples of which will be discussed later in the chapter. One advantage of using an electrolyte chain is that the reference electrode reaction need not be the same as the sensing electrode reaction, which in turn expands the choice of potential reference electrodes. In addition, the electrolyte that provides the best performance may not be commercially available or easy to fabricate. I n such cases, a commonly available, easily fabricated or low-cost electrolyte can be used for the primary structure, and a coating of the better-performing electrolyte applied to the surface. 

Electropolymerization of polymers directly onto the surface of an electrode has been used for a number of enzyme-based biosensors. By polymerizing from a solution containing the monomer, as well as the other components of the sensor, enzymes for example, a multifunctional polymer film can be fabricated. As the polymer film grows on the electrode, the enzyme and other components are entrapped in the film [9]. GOD and other enzymes have been incorporated into sensors using electropolymerization. Advantages of electropolymerization are that the film thickness can be easily controlled by the amount of polymerization charge passed, and that the polymer film is deposited only on the sensing electrode. 

Sensing Bioelectrical Signals Electrical Characteristics Practical Electrodes for Biomedical Measurements Intracavitary and Intratissue Electrodes Transparent Electrodes Microelectrodes Electrodes Fabricated Using Microelectronic... 

Kadara, R.O., Jenkinson, N. and Banks, C.E. (2009) Characterisation of commercially available electrochemical sensing platforms. Sens. Actuators, B, 138, 556. Wang, J., Tian, B., Nascimento, V.B. and Anges, L. (1998) Performance of screen-printed carbon electrodes fabricated from different carbon inks. Electrochim. Acta, 43, 3459. 

Ilyas M, Mahgoub 1 (2006) Smart dust sensor network applications, architecture, and design. Boca Raton CRC/Taylor Francis Tsai Y H (2007) Fabrication and analysis of the ascorbic acid biosensor based on the ruthenium oxide sensing electrode. Master thesis. Graduate School of Optoelectronics, National YunUn Institute of Technology, Yunlin, Taiwan... 

In terms of selectivity, lifetime, and dynamic range, the glass electrodes are superior to any other tools used for pH measuranents however, the preparation of micrometer-sized glass electrodes is not an easy task, as seen in Section 10.1.2.2. To be able to use the universal and simple micropipette electrode fabrication to pH-sensing, liquid H+-selective cocktails were also synthesized to produce micro-pH electrodes. These cocktails usually exploit the neutral tridodecylamine as active ionophore." Microelectrodes prepared with this cocktail can be used to monitor pH changes in the physiologically important pH range. 

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