Scaling of Transverse Nuclear Magnetic Relaxation due to Magnetic Nanoparticle Aggregation

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Scaling of Transverse Nuclear Magnetic Relaxation due to Magnetic Nanoparticle Aggregation

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dc.contributor.author Brown, Keith A.
dc.contributor.author Vassiliou, Christophoros C.
dc.contributor.author Issadore, David Aaron
dc.contributor.author Berezovsky, Jesse
dc.contributor.author Cima, Michael
dc.contributor.author Westervelt, Robert M.
dc.date.accessioned 2011-12-08T18:29:01Z
dc.date.issued 2010
dc.identifier.citation Brown, Keith A., Christophoros C. Vassillou, David Issadore, Jesse Berezovsky, Michael J. Cima, and R. M. Westervelt. 2010. Journal of Magnetism and Magnetic Materials 322(20): 3122-3126. en_US
dc.identifier.issn 0304-8853 en_US
dc.identifier.uri http://nrs.harvard.edu/urn-3:HUL.InstRepos:5364374
dc.description.abstract The aggregation of superparamagnetic iron oxide (SPIO) nanoparticles decreases the transverse nuclear magnetic resonance (NMR) relaxation time \(T_{2}^{CP}\) of adjacent water molecules measured by a Carr-Purcell-Meiboom-Gill (CPMG) pulse-echo sequence. This effect is commonly used to measure the concentrations of a variety of small molecules. We perform extensive Monte Carlo simulations of water diffusing around SPIO nanoparticle aggregates to determine the relationship between \(T_{2}^{CP}\) and details of the aggregate. We find that in the motional averaging regime \(T_{2}^{CP}\) scales as a power law with the number \(N\) of nanoparticles in an aggregate. The specific scaling is dependent on the fractal dimension \(d\) of the aggregates. We find \(T_{2}^{CP} \propto N^{-0.44}\) for aggregates with \(d=2.2\), a value typical of diffusion limited aggregation. We also find that in two-nanoparticle systems, \(T_{2}^{CP}\) is strongly dependent on the orientation of the two nanoparticles relative to the external magnetic field, which implies that it may be possible to sense the orientation of a two-nanoparticle aggregate. To optimize the sensitivity of SPIO nanoparticle sensors, we propose that it is best to have aggregates with few nanoparticles, close together, measured with long pulse-echo times. en_US
dc.description.sponsorship Engineering and Applied Sciences en_US
dc.language.iso en_US en_US
dc.publisher Elsevier en_US
dc.relation.isversionof doi:10.1016/j.jmmm.2010.05.044 en_US
dash.license OAP
dc.subject SPIO en_US
dc.subject nuclear magnetic resonance en_US
dc.subject T2 shortening en_US
dc.subject aggregation en_US
dc.subject clustering en_US
dc.title Scaling of Transverse Nuclear Magnetic Relaxation due to Magnetic Nanoparticle Aggregation en_US
dc.type Journal Article en_US
dc.description.version Accepted Manuscript en_US
dc.relation.journal Journal of Magnetism and Magnetic Materials en_US
dash.depositing.author Westervelt, Robert M.
dc.date.available 2011-12-08T18:29:01Z

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  • FAS Scholarly Articles [7176]
    Peer reviewed scholarly articles from the Faculty of Arts and Sciences of Harvard University

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