Silica Encapsulation of Ferrimagnetic Zinc Ferrite Nanocubes Enabled by Layer-by-Layer Polyelectrolyte Deposition

Park, Jooneon; Porter, Marc D.; Granger, Michael C.

doi:10.1021/acs.langmuir.5b00268

Cited by 19 publications

(14 citation statements)

References 60 publications

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“…These values exceed the typical values reported for Fe 3 O 4 nanoparticles in literature, varying from 300-450 kA/m, 15,52 indicating uncompensated Fe 3+ in O h sites and effective insertion of Zn 2+ in T d sites (Fig. 6c) is nominally expected for this amount of substitution [41][42][43]45,53 (see the scheme in Fig. 6c).…”

Section: (D)contrasting

confidence: 38%

The Dissociation Rate of Acetylacetonate Ligands Governs the Size of Ferrimagnetic Zinc Ferrite Nanocubes

Lak

Kahmann

Schaper

et al. 2019

ACS Appl. Mater. Interfaces

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Magnetic nanoparticles are critical to a broad range of applications, from medical diagnostics and therapeutics to biotechnological processes and single molecule manipulation. To advance these applications, facile and robust routes to synthesize highly magnetic nanoparticles over a wide size range are needed. Here, we demonstrate that changing the degassing temperature of thermal decomposition of metal acetylacetonate precursors from 90 to 25°C tunes the size of ferrimagnetic Zn x Fe 3-x O 4 nanocubes from 25 to 100 nm, respectively. We show that degassing at 90°C nearly entirely removes acetylacetone ligands from the reaction, which results in an early formation of monomers and a reaction-controlled growth following LaMer's model towards small nanocubes. In contrast, degassing at 25°C only partially dissociates acetylacetone ligands from the metal center and triggers a delayed formation of monomers, which leads to intermediate assembled structures made of tiny irregular crystallites and an eventual formation of large nanocubes via a diffusion-controlled growth mechanism. Using complementary techniques, we determine the substitution fraction x of Zn 2+ to be in the range of 0.35-0.37. Our method reduces the complexity of the thermal decomposition method by narrowing the synthesis parameter space to a single physical parameter and enables fabrication of highly magnetic and uniform zinc ferrite nanocubes over a broad size range. The resulting particles are promising for a range of applications, from magnetic fluid hyperthermia to actuation of macromolecules. File list (2) download file view on ChemRxiv Lak et al. Manuscript.pdf (4.40 MiB) download file view on ChemRxiv Lak et al. Supporting Information.pdf (1.77 MiB)

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Section: (D)contrasting

confidence: 38%

The Dissociation Rate of Acetylacetonate Ligands Governs the Size of Ferrimagnetic Zinc Ferrite Nanocubes

Lak

Kahmann

Schaper

et al. 2019

ACS Appl. Mater. Interfaces

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“…EDX elemental mapping, on the other hand, can show clearly the separation of compositions between the core and the shell in a nanometer scale. [27,33] In these studies, the accuracy of the chemical composition would not be high, but the inhomogeneous distribution of elements is obvious.…”

Section: Crystal Facets and Growth Orientationmentioning

confidence: 99%

What Can Electron Microscopy Tell Us Beyond Crystal Structures?

Zhou

Greer

2016

Eur J Inorg Chem

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Transmission electron microscopy is a powerful tool to directly image crystal structures. Not only that, it is often used to reveal crystal size and morphology, crystal orientation, crystal defects, surface structures, superstructures, etc. However, due to the 2D nature of TEM images, it is easy to make mistakes when we try to recover a 3D structure from them. Scanning electron microscopy is able to provide information on the parti-

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“…15,[17][18][19][20][21] Given the crucial importance of interactions in magnetic nanostructures, many direct and indirect approaches have been used to try to quantify them: first order reversal curve (FORC) analysis, 22,23 small angle neutron scattering, SANS, [24][25][26][27] electron holography, 28,29 magnetic force microscopy, 30,31 Lorentz microscopy, 32 Brillouin light scattering, 33 resonant magnetic x-ray scattering 34 and so on. However, one of the most accepted methods to assess interactions is the remanence plots technique (i.e., Henkel or δM plots), [35][36][37] which is routinely used to evaluate interactions between nanoparticles or grains [38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] both in fundamental studies 56,57 and in diverse nanoparticle-based applications (e.g., patterned recording media, permanent magnets, or magnetic resonance imaging 11,38,…”

Section: Introductionmentioning

confidence: 99%

Remanence Plots as a Probe of Spin Disorder in Magnetic Nanoparticles

et al. 2017

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Remanence magnetization plots (e.g., Henkel or δM plots) have been extensively used as a straightforward way to determine the presence and intensity of dipolar and exchange interactions in assemblies of magnetic nanoparticles or single domain grains.Their evaluation is particularly important in functional materials whose performance is strongly affected by the intensity of interparticle interactions, such as patterned recording media and nanostructured permanent magnets, as well as in applications such as hyperthermia and magnetic resonance imaging. Here we demonstrate that δM plots may be misleading when the nanoparticles do not have a homogeneous internal magnetic configuration. Substantial dips in the δM plots of γ-Fe 2 O 3 nanoparticles isolated by thick SiO 2 shells indicate the presence of demagnetizing interactions, usually identified as dipolar interactions. Our results, however, demonstrate that it is the inhomogeneous spin structure of the nanoparticles, as most clearly evidenced by Mössbauer measurements, that has a pronounced effect on the δM plots, leading to features remarkably similar to those produced by dipolar interactions. X-ray diffraction results combined with magnetic characterization indicate that this inhomogeneity is due to the presence of surface structural (and spin) disorder. Monte Carlo simulations unambiguously corroborate the critical role of the internal magnetic structure in the δM plots. Our findings constitute a cautionary tale on the widespread use of remanence plots to assess interparticle interactions, as well as offer new perspectives in the use of Henkel-and δM-plots to quantify the rather elusive inhomogeneous magnetizations states in nanoparticles.Additional information on the δM and the in-field Mössbauer techniques, table with the complete results of the Mössbauer spectra fits, details of the Monte Carlo simulations, FC and ZFC magnetization curves of the VST series (Fig. S1a), Langevin scaling of M(H;T) data measured in VST45 (Fig. S1b), details on the estimate of the "magnetic size" from Langevin fits, δM plots of all the VST series and graphical analysis of the intraparticle and interparticle contributions to the dip (Fig. S2), example of hysteresis loops measured after ZFC and FC (for sample VST17, Fig. S3); X-ray diffraction patterns and lattice parameter across of the maghemite cores of different size (Fig. S4); complete results from Monte Carlo simulations showing the dependence of δM on core anisotropy (Fig. S5), surface anisotropy ( Fig. S6), exchange coupling constant ( Fig. S7) and disordered surface thickness (Fig. S8).

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Silica Encapsulation of Ferrimagnetic Zinc Ferrite Nanocubes Enabled by Layer-by-Layer Polyelectrolyte Deposition

Cited by 19 publications

References 60 publications

The Dissociation Rate of Acetylacetonate Ligands Governs the Size of Ferrimagnetic Zinc Ferrite Nanocubes

The Dissociation Rate of Acetylacetonate Ligands Governs the Size of Ferrimagnetic Zinc Ferrite Nanocubes

What Can Electron Microscopy Tell Us Beyond Crystal Structures?

Remanence Plots as a Probe of Spin Disorder in Magnetic Nanoparticles

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