MAGNETIC NANOPARTICLES GENERATED BY LASER ABLATION IN LIQUID

We report on the generation of magnetic nanoparticles by nanosecond laser ablation of cobalt ferrite in liquid. We investigated the influence of both ablation liquid (water, ethanol, polyethylene glycol in water) and irradiation conditions (laser energy/pulse and spot size) on the nanoparticles dimension, shape, structure, chemical composition and magnetic properties. A single phase cobalt ferrite target was immersed in various solutions and irradiated with an Nd-YAG laser at fluences varying from 4 to 12 J/cm(2). A first characterization of the so generated colloidal solution was performed by UV-VIS absorption spectroscopy. Then, the samples were dried at 80 degrees C and the resulting material was collected for further investigations. The structural and chemical properties were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX). The nanoparticles magnetic response was recorded using a vibrating sample magnetometer (VSM). TEM micrographs revealed that the particle diameter and size distribution varied as the laser energy and irradiation spot area were modified or when polymer surfactant was added to the ablation liquid. The broad absorption band observed for all analyzed solutions was considered to be a superposition of multiple peaks associated to iron oxides. EDX measurements revealed an overstoichiometry of iron for most samples. VSM results confirmed the ferromagnetic character of the nanoparticles and their magnetic parameters were correlated to their size and chemical composition.