Effects of magnetic field gradients on the aggregation dynamics of colloidal magnetic nanoparticles

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dc.contributor.authorHeinrich, Dirk
dc.contributor.authorGoñi, Alejandro R.
dc.contributor.authorOsán, Tristán
dc.contributor.authorCerioni, L. M. C.
dc.contributor.authorSmessaert, Anton
dc.contributor.authorKlapp, Sabine H. L.
dc.contributor.authorFaraudo, Jordi
dc.contributor.authorPusiol, Daniel Jose
dc.contributor.authorThomsen, Christian
dc.date.accessioned2017-10-25T06:25:05Z
dc.date.available2017-10-25T06:25:05Z
dc.date.issued2015
dc.descriptionDieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.de
dc.descriptionThis publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.en
dc.description.abstractWe have used low-field H-1 nuclear-magnetic resonance (NMR) spectroscopy and molecular dynamics (MD) to investigate the aggregation dynamics of magnetic particles in ionic ferrofluids (IFFs) in the presence of magnetic field gradients. At the beginning of the experiments, the measured NMR spectra were broad and asymmetric, exhibiting two features attributed to different dynamical environments of water protons, depending on the local strength of the field gradients. Hence, the spatial redistribution of the magnetic particles in the ferrofluid caused by the presence of an external magnetic field in a time scale of minutes can be monitored in real time, following the changes in the features of the NMR spectra during a period of about an hour. As previously reported [Heinrich et al., Phys. Rev. Lett., 2011, 106, 208301], in the homogeneous magnetic field of a NMR spectrometer, the aggregation of the particles of the IFF proceeds in two stages. The first stage corresponds to the gradual aggregation of monomers prior to and during the formation of chain-like structures. The second stage proceeds after the chains have reached a critical average length, favoring lateral association of the strings into hexagonal zipped-chain superstructures or bundles. In this work, we focus on the influence of a strongly inhomogeneous magnetic field on the aforementioned aggregation dynamics. The main observation is that, as the sample is immersed in a certain magnetic field gradient and kept there for a time tinh, magnetophoresis rapidly converts the ferrofluid into an aggregation state which finds its correspondence to a state on the evolution curve of the pristine sample in a homogeneous field. From the degree of aggregation reached at the time tinh, the IFF sample just evolves thereafter in the homogeneous field of the NMR spectrometer in exactly the same way as the pristine sample. The final equilibrium state always consists of a colloidal suspension of zipped-chain bundles with the chain axes aligned along the magnetic field direction.en
dc.description.sponsorshipDFG, SPP 1681, Feldgesteuerte Partikel-Matrix-Wechselwirkungen: Erzeugung, skalenübergreifende Modellierung und Anwendung magnetischer Hybridmaterialienen
dc.identifier.eissn1744-6848
dc.identifier.issn1744-683X
dc.identifier.pmid26291429
dc.identifier.urihttps://depositonce.tu-berlin.de/handle/11303/6940
dc.identifier.urihttp://dx.doi.org/10.14279/depositonce-6279
dc.language.isoen
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/
dc.subject.ddc530 Physikde
dc.titleEffects of magnetic field gradients on the aggregation dynamics of colloidal magnetic nanoparticlesen
dc.typeArticleen
dc.type.versionpublishedVersionen
dcterms.bibliographicCitation.doi10.1039/c5sm00541h
dcterms.bibliographicCitation.issue38
dcterms.bibliographicCitation.journaltitleSoft matteren
dcterms.bibliographicCitation.originalpublishernameRoyal Society of Chemistryde
dcterms.bibliographicCitation.originalpublisherplaceCambridgede
dcterms.bibliographicCitation.pageend7616
dcterms.bibliographicCitation.pagestart7606
dcterms.bibliographicCitation.volume11
tub.accessrights.dnbdomain
tub.affiliationFak. 2 Mathematik und Naturwissenschaften::Inst. Festkörperphysikde
tub.affiliationFak. 2 Mathematik und Naturwissenschaften::Inst. Theoretische Physik::FG Computersimulationen und Theorie komplexer Fluidede
tub.affiliation.facultyFak. 2 Mathematik und Naturwissenschaftende
tub.affiliation.facultyFak. 2 Mathematik und Naturwissenschaftende
tub.affiliation.groupFG Computersimulationen und Theorie komplexer Fluidede
tub.affiliation.instituteInst. Festkörperphysikde
tub.affiliation.instituteInst. Theoretische Physikde
tub.publisher.universityorinstitutionTechnische Universität Berlin

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