Characterization of ferrite nanoparticles by laser desorption/ionization mass spectrometry

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Eur. J. Mass Spectrom. 4, 441 - 449 (1998)

Characterization of ferrite nanoparticles by laser desorption/ionization mass spectrometry

Andy Thierry de Ville d'Avray, Everett E. Carpenter, Charles J. O'Connor and Richard B. Cole^*
Department of Chemistry, University of New Orleans, Lakefront, New Orleans, LA 70148, USA.

ABSTRACT:

Magnetic nanoparticles are important materials used in magnetic storage media. The specific physical properties of nanophase particles can have profound effects on magnetism and will determine the merits of particular particles as components in storage devices. However, obtaining a detailed depiction of the structural features of nanoparticles is a non-trivial process. We have employed laser desorption/ionization mass spectrometry (LDI-MS) to aid in the characterization of nanoscale magnetic particles. Our investigation reports on two types of ferrite nanoparticles, having Fe₂O₃ and Fe₃O₄ crystal structures, that were each synthesized in reverse micelles. During positive and negative LDI-MS of both types of particles, iron oxide peaks were consistently produced. Compared to Fe₂O₃, Fe_{3
O₄ particles yielded more peaks at the high m/z end of the mass spectrum, and the relative intensities of higher m/z peaks were typically greater. A negative ion mode depth profiling experiment revealed the capacity of the LDI-MS approach to obtain information regarding changes in nanoparticle composition as a function of sampling depth. Over the course of prolonged irradiation of stationary Fe₂O₃ nanoparticles, distinctly different desorption/ionization behavior was observed at the particle surface as compared to the core region. The depth profiling experiment was particularly useful for distinguishing surface impurities from core constituents.}

Keywords: laser, desorption/ionization, mass spectrometry, depth profiling, ferrite, magnetic, nanoparticles, materials

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