Preparation of Ag nanoparticles by two-wavelength laser ablation and fragmentation

The work is focused on the refinement of the laser ablation method for a nanosized silver colloid preparation with regards to the nanoparticle size distribution, as well as to the reproducibility and stability of the ablated hydrosol. In the adopted procedure, additionally to the variation of the laser pulse energy, beam focusation and duration of laser ablation, we developed a technique based on further fragmentation of the ablated colloid solution by subsequent treatment with the 1064 and 532 nm nanosecond laser pulses. The method yields redistribution of nanoparticle diameters to a smaller mean size, as it was observed by transmission electron microscopy, quasielastic light scattering studies and surface plasmon (SP) optical extinction. It was shown that a similar fragmentation procedure is also effective in reduction of nanoparticle size and polydispersity of silver hydrosol prepared by routine chemical procedures and leads to a narrower SP extinction profile.