Assembly-mediated interplay of dipolar interactions and surface spin disorder in colloidal maghemite nanoclusters

Κωστοπούλου, Αθανασία; Brintakis, Konstantinos; Vasilakaki, Marianna; Trohidou, K. N.; Douvalis, Alexios P.; Lascialfari, A.; Manna, Liberato; Lappas, Alexandros

doi:10.1039/c3nr06103e

Cited by 84 publications

(108 citation statements)

References 72 publications

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“…The influence of different synthetic parameters 49 on the structural characteristics of the CNCs were carefully examined in order to attain a significant degree of size/shape homogeneity. 57 …”

Section: C1 Morphology and Crystal Structurementioning

confidence: 99%

Colloidal assemblies of oriented maghemite nanocrystals and their NMR relaxometric properties

et al. 2014

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Section: C1 Morphology and Crystal Structurementioning

confidence: 99%

Colloidal assemblies of oriented maghemite nanocrystals and their NMR relaxometric properties

et al. 2014

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“…The molecules of the capping agent "bind" on the surface of the nanocrystals introducing electrostatic repulsion between them (Figure 3). The newly formed nanocrystals tend to aggregate by oriented attachment in order to reduce their high surface energy [14,16,21,28,35,79,81,[83][84][85]87]. The balance between the opposing forces determines the size and the morphology of the secondary structures ( Figure 3).…”

Section: +3mentioning

confidence: 99%

“…The nanocluster size is determined mainly from the relative strength of the electrostatic forces between the preformed, charged nanocrystals [21]. Weaker Coulombic repulsion among the nanocrystals leads to their decreased separation in the reactant liquid, with effect in the formation of nanoclusters of larger diameter.…”

Section: +3mentioning

confidence: 99%

“…When the inter-particle interactions are very strong, the superspin moments are coupled ferromagnetically, and the assemblies are called superferromagnetic [57]. Therefore, these secondary structures can retain the magnetic behavior of the individual nanocrystals (superparamagnetic, no coercivity) [31] or can develop a new response (ferromagnetic, open hysteresis loop) [21] depending on the way their building blocks are arranged. The magnetic behavior of these complex structures is not affected exclusively by the inter-particle dipolar interactions [58], and also, the magnetic exchange [59] or other anisotropy-related terms (size, morphology, crystalline phase, or surface spin disorder) [60,61] have also been found to play a significant role ( Figure 1).…”

Section: Introductionmentioning

confidence: 99%

“…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].…”

Section: Introductionmentioning

confidence: 99%

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

Κωστοπούλου

Lappas

2015

Nanotechnology Reviews

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Magnetic particles of optimized nanoscale dimensions can be utilized as building blocks to generate colloidal nanocrystal assemblies with controlled size, well-defined morphology, and tailored properties. Recent advances in the state-of-the-art surfactant-assisted approaches for the directed aggregation of inorganic nanocrystals into cluster-like entities are discussed, and the synthesis parameters that determine their geometrical arrangement are highlighted. This review pays attention to the enhanced physical properties of iron oxide nanoclusters, while it also points to their emerging collective magnetic response. The current progress in experiment and theory for evaluating the strength and the role of intra-and inter-cluster interactions is analyzed in view of the spatial arrangement of the component nanocrystals. Numerous approaches have been proposed for the critical role of dipole-dipole and exchange interactions in establishing the nature of the nanoclusters' cooperative magnetic behavior (be it ferromagnetic or spin-glass like). Finally, we point out why the purposeful engineering of the nanoclusters' magnetic characteristics, including their surface functionality, may facilitate their use in diverse technological sectors ranging from nanomedicine and photonics to catalysis.

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Biomedical Applications of Magnetic Nanoparticles

Varadan¹,

Chen²,

Xie³

2008

Nanomedicine

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The thesis focuses on the specific design of multifunctional magnetic nano-carriers for different biomedical areas. Different shapes of core/shell bi-magnetic nanoparticle have been synthesized by seedmediated growth, and their structural and magnetic properties have been studied. The experimental results showed that core/shell nanoparticles have a higher specific absorption rate compared to the core ones. For drug delivery application, the surface of the magnetic nanoparticles is functionalized using different techniques (Diels-Alder reaction and layer-by-layer technique). More precisely, a novel bi-functional thermo-responsive system, which consists of core/shell bi-magnetic nanoparticles with furan surface functionality, is bonded with N-(2-Carboxyethyl)maleimide through Diels-Alder reaction. The chemotherapeutics doxorubicin is attached onto the surface of the nanocarriers, and a high loading efficiency of 92% is obtained. This system with high responsiveness to a high frequency external alternating magnetic field shows a very good therapeutic efficiency in hyperthermia and drug release at relatively low temperatures (50 °C). On the other hand, a switch-controlled drug release is realized by coating the core/shell bi-magnetic nanoparticle with a pH-and thermo-responsive polymer shell. Doxorubicin is loaded onto the surface of the last coating layer, and a high loading efficiency is obtained. The nano-carriers are characterized with FTIR, dynamic light scattering, Zeta potential, In vitro hyperthermia, and vibrating sample magnetometry. The in vitro drug release experiments confirm that a small amount of doxorubicin is released at body temperature and physiological pH, whereas a high drug release is obtained at acidic tumor pH under hyperthermia conditions (43 °C). The core/shell bi-magnetic nano-carriers facilitate controllable release of doxorubicin as effect of induced thermo-and pHresponsiveness of the polymer when are subjected to an high-frequency alternating magnetic field at acidic pH; thereby the drug release rate is controlled using on-off cycles of the applied field. iii KURZFASSUNG Diese Arbeit befasst sich mit der speziellen Gestaltung von multifunktionalen magnetischen Nanopartikeln für diverse biomedizinische Anwendungen. Verschiedene Formen der Kern/Schale-bimagnetischen Nanopartikel wurden durch die "seed-mediated growth" Methode synthetisiert, und die strukturellen und magnetischen Eigenschaften dieser Formen untersucht. Die Versuchsergebnisse haben gezeigt, dass die Kern/Schale-Nanopartikel eine höhere spezifische Energiea als reine Kern Partikel haben. Für die Drug Delivery Anwendung wird die Oberfläche der magnetischen Nanopartikel auf unterschiedlichen Wege (Diels-Alder-Reaktion und Layer-by-Layer-Verfahren) funktionalisiert. Dazu wurde an ein neuartiges bifunktionelles thermosensitives System, welches aus furanbeschichteten Kern/Schale bi-magnetischen Nanopartikel besteht, N-(2-Carboxyethyl) maleimid durch Diels-Alder Reaktion angebunden. Mit der Anbindung des chemotherapeutischen Doxoru...

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Assembly-mediated interplay of dipolar interactions and surface spin disorder in colloidal maghemite nanoclusters

Cited by 84 publications

References 72 publications

Colloidal assemblies of oriented maghemite nanocrystals and their NMR relaxometric properties

Colloidal assemblies of oriented maghemite nanocrystals and their NMR relaxometric properties

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

Biomedical Applications of Magnetic Nanoparticles

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