VP15-11 Size Dependence of Magneto-Optical Scattering by Superparamagnetic Nanoparticles and its Connection to Aggregation
Creators: Maarij Syed
Syed Azer Reza
Haoxiang Lu
and William Amory
Publisher: name: IEEE
Year: 2025

Superparamagnetic nanoparticles (SNPs) are increasingly deployed in biomedical applications like imaging, magnetic hyperthermia, drug delivery, etc. [1]. We present a continuation of our previous studies that examine the scattering properties of dilute aqueous suspensions of single-domain iron oxide nanoparticles using an AC Faraday rotation setup [2-4]. Our experimental approach captures both even and odd harmonics of the magneto-optical response. In this work we focus on the even harmonics that arise due to scattering. We have measured the scattering response of SNPs that vary in size from 10 to 30 nm for the longitudinal standard geometry where the applied magnetic field is along the direction of light propagation. In addition, we also discuss data that is acquired in a transverse geometry where the direction of the applied field and that of light propagation are perpendicular to each other. Our results provide important insight into the role of nanoparticle size (core and hydrodynamic) and particle concentration in the formation dynamics of clusters. While our previous work utilized the second harmonic (2f) of the received irradiance signal to analyze light scattering by SNPs subjected to an AC magnetic field, here we continue to further investigate even harmonics (primarily 2f and 4f) signal to analyze scattering but with added emphasis on the size of the SNPs. This approach allows us to investigate how scattering can be used as a useful probe for the formation of SNP aggregates. Scattering results from three different SNP sizes (samples of diameters of 10 nm, 20 nm, and 30 nm) are presented. Differences in scattering responses are then related to the structural details of the aggregates. While the main emphasis is on the SNP size as a key parameter, we have extended the measurements to different concentrations of SNPs to better investigate our framework regarding the sample properties that help (nearest-neighbor distance, effective magnetic moment) in aggregate formation.References: [1] Y. Xiao and J. Du, “Superparamagnetic nanoparticles for biomedical applications,” J. Mater. Chem. B, vol. 8, 3, 354–367, (2020). [2] S. Vandendriessche, W. Brullot, D. Slavov, V. Valev, and T. Verbiest, “Magneto-optical harmonic susceptometry of superparamagnetic materials,” Appl. Phys. Lett., vol. 102, (2013). [3] C. Patterson, M. Syed, Y. Takemaura, “Harmonic decomposition of magneto-optical signal from suspensions of superparamagnetic nanoparticles,” JMMM, 451, 248-253 (2018). [4] M. Syed, W. Li, N. Fried, and C. Patterson, “Magneto-optical investigation of scattering by superparamagnetic nanoparticles using multi-harmonic analysis,” AIP Advances 11, 015328 (2021).
Superparamagnetic nanoparticles (SNPs) are increasingly deployed in biomedical applications like imaging, magnetic hyperthermia, drug delivery, etc. [1]. We present a continuation of our previous studies that examine the scattering properties of dilute aqueous suspensions of single-domain iron oxide nanoparticles using an AC Faraday rotation setup [2-4]. Our experimental approach captures both even and odd harmonics of the magneto-optical response. In this work we focus on the even harmonics that arise due to scattering. We have measured the scattering response of SNPs that vary in size from 10 to 30 nm for the longitudinal standard geometry where the applied magnetic field is along the direction of light propagation. In addition, we also discuss data that is acquired in a transverse geometry where the direction of the applied field and that of light propagation are perpendicular to each other. Our results provide important insight into the role of nanoparticle size (core and hydrodynamic) and particle concentration in the formation dynamics of clusters. While our previous work utilized the second harmonic (2f) of the received irradiance signal to analyze light scattering by SNPs subjected to an AC magnetic field, here we continue to further investigate even harmonics (primarily 2f and 4f) signal to analyze scattering but with added emphasis on the size of the SNPs. This approach allows us to investigate how scattering can be used as a useful probe for the formation of SNP aggregates. Scattering results from three different SNP sizes (samples of diameters of 10 nm, 20 nm, and 30 nm) are presented. Differences in scattering responses are then related to the structural details of the aggregates. While the main emphasis is on the SNP size as a key parameter, we have extended the measurements to different concentrations of SNPs to better investigate our framework regarding the sample properties that help (nearest-neighbor distance, effective magnetic moment) in aggregate formation.References: [1] Y. Xiao and J. Du, “Superparamagnetic nanoparticles for biomedical applications,” J. Mater. Chem. B, vol. 8, 3, 354–367, (2020). [2] S. Vandendriessche, W. Brullot, D. Slavov, V. Valev, and T. Verbiest, “Magneto-optical harmonic susceptometry of superparamagnetic materials,” Appl. Phys. Lett., vol. 102, (2013). [3] C. Patterson, M. Syed, Y. Takemaura, “Harmonic decomposition of magneto-optical signal from suspensions of superparamagnetic nanoparticles,” JMMM, 451, 248-253 (2018). [4] M. Syed, W. Li, N. Fried, and C. Patterson, “Magneto-optical investigation of scattering by superparamagnetic nanoparticles using multi-harmonic analysis,” AIP Advances 11, 015328 (2021).