Map of the structural and optical properties of gold nanoparticles at thermal equilibrium

The remarkable relationship among the size, shape, and optical properties of gold nanoparticles is proving to be very useful in a range of high-performance applications. Considerable effort and investment is focused on delivering gold nanoparticles with precise morphologies. However, the reliability of these particles is contingent upon the morphological stability, particularly against variations in the thermodynamic environment, such as changes in temperature. Presented here are results from a combination of computational and theoretical techniques showing how the optical properties of gold nanoparticles respond to changes in the size, shape, or temperature, obtained by sampling the optical spectrum over large configuration space, in accordance with the nanoscale phase diagram. We find that spectrum from morphologies expected at small sizes is robust against temperature fluctuations, unless the concentration is very high. At larger sizes, the color will likely change with temperature, due to the accompanying change in particle shape, and this change will be noticeable when the concentration is low.