Interplay between Longitudinal and Transverse Contrasts in Fe₃O₄ Nanoplates with (111) Exposed Surfaces

Abstract

Iron oxide has been developed as either T1 or T2 magnetic resonance imaging (MRI) contrast agents by controlling the size and composition; however, the underlying mechanism of T1 and T2 contrasts in one iron oxide entity is still not well understood. Herein, we report that freestanding superparamagnetic magnetite nanoplates with (111) exposed facets have significant but interactional T1 and T2 contrast effects. We demonstrate that the main contribution of the T1 contrast of magnetic nanoplates is the chemical exchange on the iron-rich Fe3O4(111) surfaces, whereas the T2 relaxation is dominated by the intrinsic superparamagnetism of the nanoplates with an enhanced perturbation effect. We are able to regulate the balance of T1 and T2 contrasts by controlling structure and surface features, including morphology, exposed facets, and surface coating. This study provides an insightful understanding on the T1 and T2 contrast mechanisms, which is urgently needed to allow more sophisticated design of high-performance MRI contrast agents.

Colloidal magnetic nanocrystal clusters: variable length-scale interaction mechanisms, synergetic functionalities and technological advantages

“…MAR, motional averaging regime; SDR, static dephasing regime; ELR, echo-limiting regime. It is worth noting though that deviations to the proposed r 2 universal scaling law [135] have been reported for nanosystems presented with faceted [69] or nanoplate [136] morphology particles, thus, corroborating to the consequences of non-spherical particle shape, a parameter that has not been considered in the above model. In summary, upon the assembly of nanocrystals into clusters, features such as the size, magnetization, and inorganic phase volume fraction would determine the relaxivities ( Figure 20); however, other factors may also play a critical role.…”

“…In summary, upon the assembly of nanocrystals into clusters, features such as the size, magnetization, and inorganic phase volume fraction would determine the relaxivities ( Figure 20); however, other factors may also play a critical role. For example, the size distribution [25], shape/morphology [69,136], and surface characteristics (the thickness of the surfactant layer, r 2~1 /L; its hydrophilicity) [131,137] are a few parameters for which the theoretical predictions are poorly accounting for. Further on, microscopic phenomena related to the nanocluster or the constituent nanocrystal (e.g.…”

Microemulsion-mediated hydrothermal growth of pagoda-like Fe3O4 microstructures and their application in a lithium–air battery

“…In the past few years, a variety of efforts have focused on the development of new synthetic routes for fabricating various Fe 3 O 4 structures, such as octahedrons [5,6], spindles [7], rods [8,9], wires [10,11], nanobelts [12], nanoplates [13], and more complex shapes [14,15]. However, synthesis of novel pagodalike Fe 3 O 4 microstructures, which can provide a large surface area and the self-organization of these building blocks into complex ordered microstructures, still remains challenging and is of considerable interest.…”

Rare Earth Based Anisotropic Nanomaterials: Synthesis, Assembly, and Applications

“…Longitudinal relaxation enhancement is mainly related to the inner-sphere regime that chemically exchanges directly with the paramagnetic centers, while transverse relaxation enhancement is mainly related to proton's effective diffusion and interaction with magnetic dipolar moment in outer-sphere regime (Fig. 5.24) [147]. The ability of CAs to shorten longitudinal relaxation time (T 1 ) and transverse relaxation time (T 2 ) is evaluated by longitudinal relaxivity (r 1 ) and transverse relaxivity (r 2 ), respectively.…”