Iron Oxide Monocrystalline Nanoflowers for Highly Efficient Magnetic Hyperthermia

Abstract

International audienc

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

“…An enhanced SLP value of 1175 Wg -1 has been found for maghemite nanoclusters under an alternating magnetic field of 21.5 kAm -1 (at a frequency of 700 kHz) [30]. This value is similar to that observed for nanocrystals of enhanced magnetic anisotropy (nanocubes of 20 nm) [60].…”

“…In a fashion analogous to the evolution of MRI relaxivities, a range of morphologies (Figure 20), associated with different magnetic material volume fractions, variable strength dipolar interactions, and emerging microscopic mechanisms (see Section 3.2) were shown to impact heat release. The SLP has been found enhanced compared to that of individual nanocrystals when superparamagnetic nanoclusters were capped with amine [30], while the opposite effect was observed for superparamagnetic nanocrystals embedded in polystyrene (PS) nanospheres [145]. Calculation of Néel and Brown relaxation times in the latter unveiled that the Néel relaxation is faster than the Brownian and shorter than the measurement time [145].…”

“…However, humans cannot tolerate alternating magnetic field with a large H·f product, due to unwanted side effects. An alternative way to attain a better efficiency, with a lower dose and milder magnetic field conditions, is to optimize the size of the magnetic particle mediators [143,144], as well as to improve their magnetic characteristics (M S , H C , K) by tuning the composition [97,130], shape [66], and morphology [30,145]. Broadly speaking, the SLP values go through a maximum at a certain particle size and magnetic anisotropy constant.…”

“…Different morphologies, compact or loose structures with diameters ranging from 30 to a few hundred nm have been obtained with the previous synthesis strategies. Colloidal assemblies of inorganic nanocrystals are commonly called nanoclusters [15,[21][22][23][24][25][26][27][28][29], but in the literature, they can also be found as nanoflowers [30], nanoroses [17], multi-core particles [31,32], nanoassemblies [13,14,33,34], porous particles [35], flower-like mesocrystals [36], nanobeads [37,38], and pomegranate-like particles [34]. Furthermore, it is worth noting that these can be delivered with diverse chemical origin, including nanoclusters of ZnO [39,40], Co 3 O 4 [41], CuO [42], In 2 O 3 [40], CoO [40], MnO [40], ZnSe [40], CuCr 2 S 4 [43], PbS [44], and TiO 2 [45].…”

Controlling nickel nanoparticle size in an organic/metal–organic matrix through the use of different solvents

“…Using a CeO 2 matrix Abiade et al [24] were able to show that small nanoparticles (8 nm) could be tuned to have a T B higher then room temperature and that this was related to the interparticle spacing. Recent work on flower-like maghemite nanoparticles showed that the blocking temperature of iron oxide nanoparticles could be greatly enhanced if mutli-core particles were created [26,27]. It was thought that magnetic exchange between the surfaces of each particle led to an overall increase in magnetic anisotropy and a hardening of the particles.…”