Expanding the plasmonic response of bimetallic nanoparticles by laser seeding


C.E Rodríguéz

This work explores a cost-effective route to enhance the tuning range of the optical response of
metal nanostructures on substrates beyond the ranges that are achievable through the
nanostructure dimensions, composition or dewetting processes. The new route (laser seeding)
uses single nanosecond laser pulses to induce dewetting in regions of a metal layer deposited on
a glass substrate followed by the deposition of a second metal layer, both layers being deposited
by pulsed laser deposition. In order to show the possibilities of this new route, we have chosen
that the two metals were different, namely Ag and Au. The comparison of the optical response of
these regions to those that were laser irradiated after deposition of the second metal layer shows
that while nanoalloyed nanoparticles (NPs) are formed in the latter case, the NPs produced in the
former case have a heterogeneous structure. The interface between the two metals is either sharp
or a narrow region where they have mixed depending on the laser fluence used. While the
nanoalloyed NPs exhibit a single, narrow surface plasmon resonance (SPR), the heterogeneous
NPs show broader SPRs that peak in the near infrared and depending on conditions exhibit even
two clear SPRs. The laser seeding approach in the conditions used in this work allows for the
expansion of the tuning range of the color to the blue–green region, i.e. beyond the region that
can be achieved through nanoalloyed NPs (yellow–red region). In addition, the results presented
foresee the laser seeding route as a means to produce round and almost isolated NPs in an
enhanced range of diameters.

Artículo-CERG 4 2016