From wedding rings on fingers to massive ingots in government vaults, by way of Olympic medals and stained glass windows, gold has been highly prized for millennia. Its contribution to metaphor alone is legion — who would want a therapy that is, let us say, the silver standard?
Element 79 in the periodic table has a celebrated place in the history of science and technology. Ernest Rutherford figured out the basic architecture of the atom — a tiny nucleus orbited by distant electrons — by shooting alpha-particles at gold foil and seeing that most went straight through it. Michael Faraday's experiments with colloidal gold gave an early hint of today's nanotechnology revolution. And gold electrodes were used in the earliest integrated circuits — the chips that launched the information revolution.
The rising price of gold has driven mining companies to places previously deemed too difficult or expensive, and recycling plants extract large amounts of gold from discarded mobile phones, computers and other electronic jetsam (see page S4). Microorganisms can help too — bacteria have been found that make gold nanoparticles from solutions of gold salts (S12).
Nanoparticles are at the heart of gold's most exciting technological developments. Gold nanoparticles can carry drugs directly to tumours without damaging healthy tissue (S14), for example. The striking visual qualities of gold hint at remarkable properties found only at extremely small dimensions. The so-called plasmonic effect, which gives stained glass windows their iridescent beauty, is especially pronounced when using gold (S7); this property could lead to better electronic and photonic devices, such as more efficient solar cells (S8). And chemists are discovering that although gold is usually chemically inert, it can be an extremely effective catalyst (S10).
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