Ph. D. THESIS 2009

was chosen instead of an aqueous one because it generates less porous and
grainy metallic deposits [11]. The reaction was performed at room temperature
and stopped after 4 minutes to avoid the adherence of gold colloids on the
substrate surface.
a b
Figure 10. SEM images of silver structures coated in gold by EP after
4 min(a) and 10 min(b); (c) colloid detail.
Outside of the woodpile we find no change as compared to before the AuCl4
treatment, which shows that the treatment is efficient only in the areas where
Ag was present.
4 Optimisation of gold nanostructures fabrication
Gold is a well-known noble metal, which is not affected by air, moisture,
oxygen, and other corrosive agents, making it well-suited for wide fields
applications. Different techniques using light to fabricate gold nanostructures
were developed because its already known applications in photographic art as
well as for the new applications in nanophotonics and nanoelectronics, as well
as in biology imaging and sensing [12].
Why gold instead of already well-demonstrated efficiency of silver in
photographic art? Gold as metal exhibits a high stability in contact with
atmospheric ambiance.
4.2. UV-Vis investigation
Preliminary experiments were performed in dilute solution in order to validate
the gold ions photoreduction process. In that case UV exposure (one photon)
can be used to validate the process.
Figure 11 a) and b) shows typically UV-Vis spectra recorded after irradiation in
solution and thin film of gold salt and ammonium ferric citrate mixture in PSS,
irradiated at every 20, and 15 minutes, respectively.
7