The weird world of nanoscale gold

Protagonists in the emerging field of nanotechnology have as their objective the design, construction and study of useful devices based on nanoscale materials and objects. Objects or structures that have at least one important dimension in the range 0.5 to perhaps 50 nm may be considered to be in the nanoscale domain. These sizes lie far below the 200 nm or so that can be resolved with an optical microscope, and are closer in size to the 0.3 nm diameter of individual atoms. The field of nanotechnology is attracting keen interest at present. The excitement is motivated by the observation that control of matter at the nanoscale holds the promise of, amongst others, faster computing, better medicines, and more useful materials. In this paper, the physical phenomena on which this optimism is based are broadly discussed and explained. Where appropriate, examples of the rather different and curious properties of gold at the nanoscale are used to illustrate the points covered.