Modification of microelectrode arrays: new microelectrochemical devices for sensor applications

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Abstract
Microelectrode arrays consisting of two or eight closely spaced (ca.1 μm) gold or platinum microelectrodes (approximate dimensions 2 μm wide x 50 μm long x 0.1 μm high) can be modified with a variety of redox-active materials in a way that leads to microelectrochemical devices that may be useful as sensors. In general, a pair of microelectrodes connected by a redox-active material represents a device, because the current, Id, passing from one microelectrode (source) to the other (drain) at a fixed potential between them, Vd, can be modulated by electrically or chemically induced changes in the state of charge of the redox material. The fundamental issues associated with pH-sensitive devices based on poly(3-methylthiophene), poly(4-vinylpyridine), a viologen—quinone redox polymer and WO3are described to illustrate generic concepts that underlie the development of microelectrochemical sensors.