Fabrication of high-demensional nano-structures by laser ablation in liquids

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Laser irradiation onto metal nanoparticles is one of a essential technique to modify the shape of the nanoparticles. While former studies using nanoparticles obtained by chemical synthesis have shown that only size-decreased or -increased spherical nanoparticle were obtained, we revealed that nanowires were obtained by laser irradiation onto silver nanoparticles prepared by laser irradiation in pure water.In this study, the formation mechanisms of the nanowires have been explored. First, we have investigated the influence of the irradiation intensity on the shape of products, and have revealed that nanowires and sheets were produced at high irradiation intensity. This finding indicates that nanowires will be produced via fusion of silver nanoparticles. In addition, nanoprisms and nanorods were found to be produced at low laser intensity, indicating that another type of shape conversion presents.Second, we have investigated influences of ions contained as impurities on the formation of nanowires. The formation efficiency and size of wire-like particles increased with increase in the concentration of NaCl. This finding can be explained in terms of the ion-mediated self-assembly of metal nanoparticles. In addition, it was found that the formation of nanoprisms and nanorods were enhanced by addition of NaCl. This finding was explained in terms of the oxidative etching effect by chloride ions on silver nanoparticles followed by photo-reduction.In the future study, we will carry out further investigation on the formation mechanism of nanoprisms and nanorods.