Size and Temperature Dependence of the Plasmon Absorption of Colloidal Gold Nanoparticles

TLDR

The study examined size and temperature effects on plasmon absorption of gold nanoparticles (9–99 nm) in aqueous solution, modeling dephasing with a two‑level approach that yielded sub‑5 fs lifetimes, and assessed temperature dependence. Plasmon bandwidth increases with decreasing size below 25 nm and with increasing size above 25 nm, indicating homogeneous size distribution and homogeneous broadening across samples, while a small temperature effect was observed, consistent with electron–electron dominated dephasing.

Abstract

The size and temperature dependence of the plasmon absorption is studied for 9, 15, 22, 48, and 99 nm gold nanoparticles in aqueous solution. The plasmon bandwidth is found to follow the predicted behavior as it increases with decreasing size in the intrinsic size region (mean diameter smaller than 25 nm), and also increases with increasing size in the extrinsic size region (mean diameter larger than 25 nm). Because of this pronounced size effect a homogeneous size distribution and therefore a homogeneous broadening of the plasmon band is concluded for all the prepared gold nanoparticle samples. By applying a simple two-level model the dephasing time of the coherent plasmon oscillation is calculated and found to be less than 5 fs. Furthermore, the temperature dependence of the plasmon absorption is examined. A small temperature effect is observed. This is consistent with the fact that the dominant electronic dephasing mechanism involves electron−electron interactions rather than electron−phonon coupling.