Designer electrodes

Specially designed electrodes in which the electrode tip is covered in a gel containing the appropriate oxidase are commercially available. A semipermeable membrane retaining the gel, and permitting oxygen diffusion, completes the assembly. 

Matousek, R.M. Romine, R.L. (1998) New and Improved Diaphragm Cell Hardware Designs. ELECTRODE Corporation Chlorine/Chlorate Seminar. 

In classical polarographic techniques, a dropping mercury electrode is used. This is a complex device in which continuously produced small droplets of mercury are used as the active electrode in order to prevent poisoning of the electrode and to provide constant conditions throughout the analysis. For many applications, specifically designed electrodes are available which are simpler to use. 

Murray R.W. (1992) in Molecular Design of Electrode Suifaces Introduction to Molecularly Designed Electrode Suifaces (ed. R.W. Murray), John Wiley and Sons, Inc., New York. 

Clever chemists have designed electrodes that respond selectively to specific analytes in solution or in the gas phase. Typical ion-selective electrodes are about the size of your pen. Really clever chemists created ion-sensing field effect transistors that are just hundreds of micrometers in size and can be inserted into a blood vessel. The use of electrodes to measure voltages that provide chemical information is called potentiometry. 

It is more than probable that arrays for 50-100 DNA sequences will be needed for some clinical applications. Although it is not difficult to design electrode pads with reproducible dimensions of a micron or less, the electrochemical readout requires mechanical connections to each individual electrode. Therefore, the construction of very large, multiplexed arrays presents a major engineering challenge. Electronic switches in the form of an on-chip electronic multiplexer may provide a possible solution for this problem. 

Some of the very interesting applications of these layered intercalates are in material design [3], ion exchange [4], catalysis [5], in the study of quantum-sized semiconductor particles [6], assembly of molecular multilayers at solid-liquid interfaces [7], designer electrode surfaces [8], preparation of low-dimensional conducting polymers [9], and so forth. 

There are examples of designer electrodes in which two materials are necessary. For example, (Ru(NH3)6)3+/2+ serves to transport electrons by means of a hopping... 

The method differs from most others in that initially the electrodes are at ambient temperature and that in semi-continuous production the temperature of the electrodes increases only through conduction of heat from the materials being joined. With well-designed electrodes the operating temperature seldom exceeds 40 °C. 

The experimental aspects to be discussed in this chapter include cell design, electrode materials, construction and cleaning of electrodes, solution composition, and control instrumentation. Electrode materials specially designed for potentiometric measurements, which rely on the material selectivity, are discussed in Chapter 13. 

Electroporation efficiency depends on the parameters of electric pulses that are delivered to the treated cells using specially designed electrodes and electronic devices. In vitro experiments usually employ parallel plate types of electrodes made of inert metals like stainless steel or platinum but needle types of electrodes are also used for tissue electroporation [24,25,27,28] as well as for tumor treatment apphcations [29-32]. There are two types of electroporator devices available devices with voltage output and those with current output. However, a voltage output device seems to be preferable, which is widely used for diverse applications. 

Nondestructive analysis of solid HTSC oxides is based on voltammetric [42,45,62, 534] and chronopotentiometric [62] investigations of specially designed electrodes which contain microquantities of HTSC (paraffined graphite with the oxide powder pressed on the top [43-45] and carbon paste electrodes [34-41]). Analytical details are thoroughly documented for such systems (including HTSCs and other multi-component materials) [535-537]. 

Another reason for designing electrodes of a certain size is the combination of weight loss with electrochemical measurements. Thus, very small electrodes should not be used when gravimetric measurements are required. 

Using a combination of a dc resistance measuring meter (highly sensitive ohmmeter with a specially designed electrode) and a capacitance-type meter, a measure of moisture distribution in corn kernels can be obtained. This information has been used to detect heat damage in artificially dried corn [81,82]. 

The reality is that surface electrode modification is needed to make the ultramicroelectrode material selective for NO. Therefore, the design of modified electrode surfaces using organized layers is very attractive and provides the ideal strategy. In the general case, the chemical modification of electrode surfaces with polyelectrolytes and metal complex-based polymer films has expanded the scope of appUcation of such designed electrodes and provided a lot of options for then-use in various experimental conditions. In addition to their electrocatalytic applications, such electrodes showed a great promise for electroanalysis. As far as this aspect is concerned, substantial improvements in selectivity, sensitivity, versatiUty and reproducibility can be achieved. 

---