Chemistry Reference
In-Depth Information
Fig. 6 Relaxation behavior
of excited electrons in three
differently sized AuNPs.
Figure reprinted with kind
permission from [
23
]
treated by femtosecond laser pulses, the corresponding relaxation times are size
dependent. They are very different between Au
55
and the other two species. The
relaxation time is dependent on the electron-phonon coupling and the electron
surface collision. In larger particles it is dominated by the weakening of the
electron-phonon coupling, resulting in a slowdown of the relaxation. On the way
from 15 to 1.4 nm, electron surface collision increases and consequently the
relaxation time decreases. On the other side, the 0.7 nm Au
13
cluster behaves
molecular-like due to the fixed electrons between the Au atoms. Its relaxation is
very slow. These results impressively demonstrate Au
55
clusters to behave like
species just one step before molecular and one step behind metallic state. These
correlations can be followed from Fig.
6
.
Up to here, we have discussed the influence of size, structure, and electronic
properties on the relevance concerning bioresponse. However, there is another, very
important factor: the protecting ligand shell. As already mentioned above, the use
