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

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.

Bimetallic nanoparticles were fabricated by using a focused Nd:YAG nanosecond laser source emitting a 1064nm wavelength radiation and characterized with ζ-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 (514.5nm) and far-red (785nm) excitation wavelengths.

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.