Cubic Mesocrystal Magnetic Iron Oxide Nanoparticle Formation by Oriented Aggregation of Cubes in Organic Media: A Rational Design to Enhance the Magnetic Hyperthermia Efficiency

Abstract

Magnetic iron oxide mesocrystals have been reported to exhibit collective magnetic properties and consequently enhanced heating capabilities under alternating magnetic fields. However, there is no universal mechanism to fully explain the formation pathway that determines the particle diameter, crystal size, and shape of these mesocrystals and their evolution along with the reaction. In this work, we have analyzed the formation of cubic magnetic iron oxide mesocrystals by thermal decomposition in organic media. We have observed that a nonclassical pathway leads to mesocrystals via the attachment of crystallographically aligned primary cubic particles and grows through sintering with time to achieve a sizable single crystal. In this case, the solvent 1-octadecene and the surfactant agent biphenyl-4-carboxylic acid seem to be the key parameters to form cubic mesocrystals as intermediates of the reaction in the presence of oleic acid. Interestingly, the magnetic properties and hyperthermia efficiency of the aqueous suspensions strongly depend on the degree of aggregation of the cores forming the final particle. The highest saturation magnetization and specific absorption rate values were found for the less aggregated mesocrystals. Thus, these cubic magnetic iron oxide mesocrystals stand out as an excellent alternative for biomedical applications with their enhanced magnetic properties.

Advancements in enzyme immobilization on magnetic nanomaterials: toward sustainable industrial applications

“…195 Enzyme immobilization on MNPs can reduce M s if a biopolymer-based coating imparts a diamagnetic quality. 188 Coating MNPs improves multifunctionality and biocompatibility, 196 with both aggregation 197,198 and crystalline anisotropy 197 influencing M s .…”

Nanoparticles with cubic symmetry: classification of polyhedral shapes

“…Cu [26][27][28], Au [25], Pt [16]) and oxidic (e.g. Cu 2 O [32], Fe 3 O 4 [7][8][9][10], MgO [13]). According to (2b) and ( 3), these polyhedra are confined by all 6 {100} facets with facet distances R 100 defining, as expected, the cubic polyhedron, see figure 1(a).…”

“…An analysis shows that all 12 facets are of the same rhombic shape where each {110} facet extends between adjacent corners C {100} and C {111} , such as C (100) , C (111) , C (001) , C (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11) . The resulting four edges connect corners, such as C (100) with C (111) , at distances d b1 given by…”

“…Examples are applications in medicine [6][7][8], of magnetism [7][8][9][10], or in catalytic chemistry where metal and oxide NPs have become ubiquitous [11][12][13][14][15][16][17][18].…”

“…Their overall shape often reminds of compact sections confined by simple polyhedra where particles of material forming cubic bulk lattices [5,19,20] are found to exhibit, apart from hexagonal [21] and icosahedral geometry [22,23], generic polyhedra of cubic symmetry, such as cubes and octahedra. Examples are NPs of metals, such as Au [24][25][26], Cu [26][27][28], Rh [17], Pd [14,15,17,29], Pt [16,17,30], or of oxides and bromides, such as CeO 2 [31], Cu 2 O [32], MgO [13], spinel Fe 3 O 4 [7][8][9], CuBr [33], forming cubes and octahedra. Only selected other polyhedral shapes of cubic symmetry, like tetrahexahedral, have been observed for Pt NPs [10,17,18,30,34].…”