Chapter 6: Nanoelectrodes in electrochemical analysis

David Hubel is widely acknowledged as the first person (in the late 1950s) to have fabricated metal microelectrodes that consisted of an insulated tungsten wire with an exposed electrolytically sharpened tip (B0.4-10 mm).1,2 In the intervening years, microfabrication techniques, borrowed from the microelectronics industry, have enabled routine and facile fabrication of electrodes with a critical dimension on the order of less than ten microns down to around a few hundreds of nanometres. These electrodes are generally classified as ultra-microelectrodes with a critical dimension of o25 mm. The fabrication and the investigation of electrochemical properties of these ultra-microelectrodes are well documented in the literature.3-6 More recently, the trend to miniaturisation to realise further enhanced electrochemical performance has driven development and fabrication of electrodes with a critical dimension in the range of 1 to 100 nm-defined as nanoelectrodes. Early investigations into the use of nanoelectrodes in electrochemistry were based on advances in micro and ultra-micro fabrication techniques. For example, in the late 1980s Morris et al. first fabricated platinum and gold nanoband electrodes by depositing platinum or gold onto smooth mica followed by encapsulating all but one edge of the film in epoxy.7 Since then, with ever-increasing sophistication of methods to produce materials at the nanoscale, nanoelectrodes have opened up new research domains and application opportunities in many areas of electroanalysis, in the environment,8 health9,10 and security11 sectors.