Laser ablation in liquid: a route for fabrication of noble metal and oxide nanostructures composed colloids

We have synthesized Au, Ag and ZnO nanoparticles (NPs) by nanosecond pulsed laser ablation in liquids using three different targets: Au, Ag and ZnO. We used ethanol, chloroform and toluene as liquid media. All ablation experiments are performed by the fundamental wavelength (1064 nm) of a Nd:YAG laser as the laser fluence used is 12 J/cm². The optical properties of the colloids are evaluated by optical transmittance measurements in the UV-VIS spectral range. The morphology of the NPs created and the evaluation of their size distribution are investigated by transmission electron microscopy. Selected area electron diffraction (SAED) is employed for chemical phase identification of the created nanostructures. Predominantly spherical and spherical-like NPs are formed at the different combination of targets and liquids used as the mean particles diameter varies in the range of 3 to 20 nm for the different cases. A single well defined surface plasmon resonance (SPR) band in the optical absorption spectra of the Au and Ag colloids produced by laser ablation in ethanol is observed in contrast to the case of ablation in toluene. In the case of ablation in chloroform only the Au colloid exhibits plasmon behaviour. The absence of a SPR property of the Au and Ag particles in toluene and Ag NPs in chloroform is due to the formation of carbon matrix around the NPs in the colloid. The phase identification of NPs produced by laser ablation of ZnO target in ethanol, chloroform and toluene demonstrates the presence of hexagonal ZnO. In the cases of ablation in chloroform and toluene unidentified interplanar spacing in the corresponding SAED patterns are observed, which means that other phases and compounds are formed in the ablation process. Key words: noble metal NPs, ZnO NPs, laser ablation in liquid, colloidal inks, organic solvents