Laser-assisted generation of elongated Au nanoparticles in aqueous solutions of divalent ions

One-step laser-assisted fabrication of elongated Au nanoparticles (NPs) and their subsequent fragmentation and agglomeration are experimentally studied. The generation of elongated Au NPs is carried out via laser ablation of a solid Au target in water using an ytterbium-doped fiber laser source with pulse duration of 200?ns and pulse energy of 1?mJ. Extinction spectrum of the resulting particles exhibits an increase in the absorption in visible red and near IR spectral regions. This change in absorption is accounted for by the longitudinal plasmon resonance of the electrons in elongated Au NPs and is corroborated by the TEM images. The effect of additional laser exposure on the elongated Au NPs produced using this method is studied, as well. Laser pulse energies and exposure times are varied. Possible processes of laser-assisted formation of elongated Au NPs in aqueous solutions of calcium chloride and magnesium sulfate and their following interaction with pulsed laser radiation are discussed.