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Sizing and Eddy currents in magnetic core nanoparticles: an optical extinction approach
Luis J Mendoza Herrera1, Ignacio J Bruvera1, Lucía B Scaffardi2
1Centro de Investigaciones Ópticas (CIOp) (CONICET-CIC-UNLP) Cno, Parque Centenario e/505 y 508 Gonnet, C.C. 3 (1897) Gonnet, Buenos Aires, Argentina. daniels@ciop.unlp.edu.ar.
Physical Chemistry Chemical Physics : PCCP
|January 13, 2017
Summary
This study enhances optical extinction analysis for nanoparticles by incorporating Eddy currents into Mie theory. This provides accurate structural information, like size and shell thickness, for magnetic and plasmonic nanoparticles.
Area of Science:
- Nanotechnology
- Materials Science
- Physical Chemistry
Background:
- Optical extinction spectroscopy is crucial for studying nanoparticles in their native state.
- Extinction spectra analysis can reveal structural properties like core size distribution and coating thickness.
- Existing models often neglect magnetic and Eddy current effects in complex nanoparticle systems.
Purpose of the Study:
- To develop an advanced optical extinction model for single and multilayer nanoparticles (Fe3O4, Fe3O4@Au, Fe3O4@SiO2@Au).
- To investigate the impact of Eddy currents on optical extinction spectra.
- To determine the validity ranges of different theoretical approaches for nanoparticle analysis.
Main Methods:
- Solving full Mie theory with frequency-dependent susceptibility derived from the Gilbert equation.
- Incorporating Eddy current effects into the theoretical model.
- Comparing results with non-magnetic Mie theory, magnetic dipolar approximation, and magnetic Mie theory without Eddy currents.
Main Results:
- Novel insights into Eddy current effects on optical extinction were obtained.
- Accurate particle size and shell thickness information was derived from experimental extinction spectra of Fe3O4 and Fe3O4@Au nanoparticles.
- Experimental results showed good agreement with Transmission Electron Microscopy (TEM) data.
- Plasmon peak parameters for Fe3O4@SiO2@Au nanoparticles were successfully predicted.
Conclusions:
- The advanced Mie theory model accurately characterizes optical extinction in magnetic and plasmonic nanoparticles.
- Eddy current inclusion is vital for precise structural determination of nanoparticles using optical extinction.
- This method offers a reliable approach for nanoparticle characterization and material design.
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