Bifunctional Fe3O4/Ag nanoparticles obtained by two-step laser ablation in pure water

Hypothesis: Bimetallic nanoparticles made of iron oxide and Ag could be fabricated by pulsed laser ablation of iron and silver targets in pure water by a two-step route. These nanoparticles could exhibit both magnetic and plasmonic properties. Experiments: Bimetallic nanoparticles were fabricated by using a focused Nd:YAG nanosecond laser source emitting a 1064 nm wavelength radiation and characterized with zeta-potential, Dynamic Light Scattering (DLS), UV-vis absorption, Transmission Electron Microscopy (TEM), High Resolution TEM (HRTEM), Energy Dispersive X-ray Spectrometry (EDX), and Selected Area Electron Diffraction (SAED). The magnetic character of the nanoparticles was ascertained by observing attraction by a magnet and complete removing from the water environment, while their SERS (surface-enhanced Raman scattering) response was checked by decorating them with 2,2'-bipyridine as molecular reporter and performing Raman tests with green (514.5 nm) and far-red (785 nm) excitation wavelengths. Findings: The observed magnetic attraction was due to magnetite (Fe3O4), the only ferromagnetic iron oxide form evidenced by the characterization tests in the aqueous colloidal system, where silver nanoparticles were also embedded. UV-vis and SERS spectra confirmed the presence of nanostructured silver as plasmonic constituent of the fabricated metal nanoparticles. (C) 2016 Elsevier Inc. All rights reserved.