Silver nanorods produced by femtosecond laser pulses

Abstract

In this work we describe the study of a photoinduction method to produce silver nanorods using femtosecond laser pulses irradiation of silver solutions. The start solutions were prepared by mixing autopolymerizable resin and AgNO3 with water solutions, and illuminating those with a Xenon lamp. Various concentrations and irradiation times were used, and these irradiation processes produce spherical silver nanoparticles with sizes ranging from 30 to 100 nm. Afterwards, 30 femtosecond ultrashort pulses with energy around 200 microjoules were used to irradiate the nanoparticles solutions. All solutions were characterized by ultraviolet-visible spectroscopy and TEM microscopy. We observed that these ultrashort pulses irradiations, besides decreasing the spherical nanoparticles sizes, can create nanorods depending on the irradiation parameters. No additives, such as solvents, surfactants or reducing agents, were used in the procedures. The spherical nanopaticles size reduction can be explained by a multiphoton process that promotes the photoexcitation of surface the plasmon band, charging the particles up to the limit were Coulombic rupture occurs due to charge excess, resulting in size reduction. In the early stage of the process, the majority of smaller silver particles are directed to growing into nanorods with uniform diameters in the range from 3 to 6 nanometers. The nanorods solutions have high water solubility, good colloidal stability, stable fluorescence properties, and are amenable in deriving various functional nanoprobes.