Abstract
Metallic nanoparticles are important on several scientific, medical and industrial areas. The control of nanoparticles
characteristics has fundamental importance to increase the efficiency on the processes and applications in which they are
employed. The metallic nanoparticles present specific surface plasmon resonances (SPR). These resonances are related
with the collective oscillations of the electrons presents on the metallic nanoparticle. The SPR is determined by the
potential defined by the nanoparticle size and geometry.
There are several methods of producing gold nanoparticles, including the use of toxic chemical polymers. We already
reported the use of natural polymers, as for example, the agar-agar, to produce metallic nanoparticles under xenon lamp
irradiation. This technique is characterized as a “green” synthesis because the natural polymers are inoffensive to the
environment.
We report a technique to produce metallic nanoparticles and change its geometrical and dimensional characteristics using
a femtosecond laser. The 1 ml initial solution was irradiate using a laser beam with 380 mW, 1 kHz and 40 nm of bandwidth
centered at 800 nm.
The setup uses an Acousto-optic modulator, Dazzler, to change the pulses spectral profiles by introduction of several orders
of phase, resulting in different temporal energy distributions. The use of Dazzler has the objective of change the gold
nanoparticles average size by the changing of temporal energy distributions of the laser pulses incident in the sample. After
the laser irradiation, the gold nanoparticles average diameter were less than 15 nm.
