Resolving ambiguities in core size determination of magnetic nanoparticles from magnetic frequency mixing data

  • Frequency mixing magneticdetection(FMMD) has been widely utilized as a measurement technique in magnetic immunoassays. It can also be used for characterization[1]and distinction[2](also known as “colorization”) ofdifferent types of magnetic nanoparticlesaccording totheircore sizes.It is well known that the large particles contribute most of the FMMD signal. Typically, 90% of the signal stems from the largest 10% of the particles [1]. This leads to ambiguities in core size fitting since thecontribution of thesmall sized particles is almostundetectable among the strong responses from the large ones. In this work, we report on how this ambiguity can be overcome. Magnetic nanoparticle samples from Micromod (Rostock, Germany) were prepared in liquid and filterbound state. Their FMMD response at mixing frequencies f1 ± nf2 to magnetic excitation H(t)=H0+H1sin(2 f1t)+H2sin(2 f2t),with H1=1.3mT/μ0 at f1=40.5kHzandH2=16mT/μ0 at f2=63Hz,was measured as a function ofoffset field strength H0= (0,…,24) mT/μ0.The signal calculated fromLangevin model in thermodynamic equilibrium[1]with a lognormal core size distribution fL(dc,d0, ,A) = Aexp(–ln²(dc/d0)/(2 ²))/(dc (2 )1/2)was fitted to the experimental data. For each choice of median diameter d0, pairs of parameters ( ,A) are found which yield excellent fit results with R²>0.99.All the lognormal core size distributions shown in Figure (a) are compatible with the measurements because their large-size tails are almost equal. However, all distributions have different number of particles and different total iron content. We determined the samples’ total iron mass with inductively coupled plasma optical emission spectrometry(ICP-OES) and, out of all possible lognormal distributions, determined the one with the same amount of iron. With this additional externally measured parameter, we resolved the ambiguity in core size distribution and determined the parameters (d0, ,A).

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Metadaten
Author:Ali Mohammad Pourshahidi, Ulrich M. EngelmannORCiD, Andreas Offenhäusser, Hans-Joachim KrauseORCiD
Document Type:Conference Poster
Language:English
Year of Completion:2022
First Page:82
Note:
13th International Conference on the Scientific and Clinical Applications of Magnetic Carriers, London, United Kingdom, June 14-17, 2022
Poster 69
Link:https://magneticmicrosphere.com/ckfinder/userfiles/files/Abstract_Booklet_Magmeet_2022.pdf
Zugriffsart:weltweit
Institutes:FH Aachen / Fachbereich Medizintechnik und Technomathematik
FH Aachen / INB - Institut für Nano- und Biotechnologien