The Royal Bank Plaza building in Toronto's financial district has more than 14,000 windows, which is a lot of glass, and each of them is coated with a thin layer of gold, which is a lot of precious metal — the gold on the windows is worth over $1 million according to estimates1. By reflecting heat and infrared radiation, the gold coating reduces heating and ventilation costs in the building. Although the use and importance of gold in the worlds of jewellery and finance are well known, the 79th element in the periodic table is also found in many less glamorous applications, as this example and a recent report from the World Gold Council makes clear2.

Researchers are investigating the use of gold nanoparticles in cancer treatment.

In many ways gold is a classic nanomaterial. It is chemically inert in its bulk form. Indeed, in the past gold was “often regarded as a rather boring element from a chemical perspective” according to one leading chemist3. However, gold nanoparticles are anything but inert, and their ability to catalyse a number of important chemical reactions has been the focus of much research over the past decade, although it remains to be seen if gold nanocatalysts can be transferred from the research laboratory to the world of industry4.

One of gold's main advantages for many applications is that it does not oxidize. It is also malleable and ductile, a good conductor of electricity, and is not toxic. One can read papers about research that takes advantage of some or all of these properties in most issues of any journal that covers nanotechnology. The source and drain contacts in experiments on nanoelectronic devices, for example, are often made from gold (or gold and titanium) that has been deposited with lithographic techniques. And when researchers observed molecular orbital gating in a single-molecule transistor for the first time last year, the device had started out as a gold nanowire coated with the molecules5. And gold is still capable of springing surprises. On page 218 of this issue, for example, Jun Lou and co-workers report that it is possible to form a weld between two gold nanowires by simply bringing them into contact with each other.

The World Gold Council report focuses on two main areas: the environment and health. Environmental applications include water purification, fuel cells, solar cells and improved catalysts (which would increase the efficiency of a wide range of industrial processes). In medicine, a large community of researchers is investigating the use of gold nanoparticles in cancer treatment: the basic aim here is to develop systems that can recognize diseased cells and tissues, thus reducing harmful side effects by ensuring that powerful cancer drugs are delivered to tumours and not to healthy tissue. There are also drug-free approaches that involve heating the nanoparticles with radiation so that they 'fry' the tumour. Early detection of the recurrence of prostate cancer after surgery is yet another application6.

Gold has been very good for nanotechnology and this looks set to continue.