Spherical and Cubic Nanoparticles: Structure-Property Relationships and Enzymatic Synthesis and Degradation



Journal Title

Journal ISSN

Volume Title



Defining the influence of the shape of magnetic nanoparticles (MNPs) on their magnetic properties continues to challenge the research community. There exists a small amount of comparative data for MNPs less than 25 nm, but data for larger sizes are sorely lacking. This gap in the available data motivated my pursuit of a comparison of the magnetic properties of larger cubic and spherical Fe3O4 MNPs (>100 nm), leading to a conclusion that such comparisons should consider the degree of crystallinity of the MNPs. For MNP applications involving sensing, geometries other than spherical are preferred, where large contact areas and the resulting stronger binding to the sensor platform should lead to enhanced sensitivity. Therefore, I initially focused my research on the synthesis of cubic magnetic FeCo nanocubes with high saturation magnetization. Finally, to functionalize these nanoparticles for use in sensing, it was necessary to coat them with a thin protective layer while retaining their cubic shape. This goal was accomplished by using a silica coating followed by amine functionalization for FeCo nanocubes.
Magnetic biosensing currently employs already-synthesized MNPs and giant magnetoresistive (GMR) sensors. The use of MNP labels in bioassays and diagnostics is attractive because it can overcome concerns associated with optical sensing, which relies on substrate modification to form a product that absorbs, fluoresces, luminesces, or transforms to an insoluble precipitate. The enzyme-mediated synthesis of MNPs is a new concept for magnetic sensing in which the magnetic reporter can be enzymatically synthesized in situ. The development of this project also encouraged the pursuit of a diametrically opposite system in which the magnetic component would lose its magnetism through an enzymatically-mediated reduction process. Both approaches show potential for structuring assays that use a magnetic signal that either appears or disappears in the presence of a specific enzyme.
To summarize, my research has focused on two primary goals: (1) the chemical synthesis and functionalization of spherical and cubic MNPs and (2) the enzymatically-mediated synthesis or disappearance of MNPs that can be potentially used in a sensing assay.



Structure-shape-magnetic property, Enzymatic synthesis of magnetic nanoparticles


Portions of this document appear in: Kolhatkar, Arati G., Ivan Nekrashevich, Dmitri Litvinov, Richard C. Willson, and T. Randall Lee. "Cubic silica-coated and amine-functionalized FeCo nanoparticles with high saturation magnetization." Chemistry of Materials 25, no. 7 (2013): 1092-1097. And in: Kolhatkar, Arati G., Andrew C. Jamison, Dmitri Litvinov, Richard C. Willson, and T. Randall Lee. "Tuning the magnetic properties of nanoparticles." International journal of molecular sciences 14, no. 8 (2013): 15977-16009.