Abstract

The vibrant ruby red colours of gold nanoparticles have enthralled people as early as the Roman era, and the curious interactions of metal particles with light have been employed in e.g. stained glass ever since. However, it was Michael Faraday who first correlated these unique optical properties with the size of the particles, and who was able to reproducibly manufacture colloidal suspensions of gold. Since then, science has come a long way, and a better understanding of these nanophotonic phenomena now allows us to use gold particles to detect minute traces of molecules and even to track the behaviour of single molecules and atoms in real-time. These nanoscale optical properties will play a key role in emerging technologies.