Abstract
Pulsed laser-induced morphological transformation and size-reduction of colloidal gold nanoparticles in
the aqueous phase were investigated using transient absorption spectroscopy and transmission electron
microscopy (TEM). Femtosecond laser-induced fragmentation of gold nanoparticles within 100 ps after
the laser pulse is interpreted in terms of the Coulomb explosion mechanism. On the other hand,
nanosecond laser-induced size-reduction of gold nanoparticles is in good agreement with the
photothermal evaporation mechanism that is based on heating of particles to temperatures above the
boiling point of gold (3100 K). Here, the experimentally observed fragmentation thresholds were wellreproduced
by simulations based on electron and lattice temperature models and by considering the
dissipation of heat into the surrounding medium. The numerical method described herein has the
advantage of identifying the fragmentation mechanism by considering pulse duration- and energydependent
thresholds. To-date there is no other convenient measures to distinguish between the
photothermal evaporation and the Coulomb explosion mechanisms.
