Optical properties of gold nanostructures

The optical properties of gold in the visible are dominated by the response of the free conduction electrons to light. In gold nanostructures, the surface charge density adopts a configuration that is constrained by the shape of the nanoparticles. As a result, the scattering of light by gold nanoparticles exhibits a resonant response characterised by a strong scattering and absorption in a narrow range of frequencies. The spectral range of this localised surface plasmon resonance (LSPR) can be tuned by varying the size and shape of the gold nanoparticle – the nanoparticles act as nanoscale antennas for the visible light.