Predicting the Self‐Assembly of Superparamagnetic Colloids under Magnetic Fields

Faraudo, Jordi; Andreu, Jordi S.; Calero, Carles; Camacho, J.

doi:10.1002/adfm.201504839

Cited by 109 publications

(125 citation statements)

References 80 publications

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“…[11][12][13][14][15] More recently, some researchers have shown that more complex deposit structures can be achieved thanks to various concentrations of liquid crystals [16]. In this paper, we demonstrate that magnetic interactions between superparamagnetic colloidal particles [17][18][19][20][21] can be used to control the properties of colloidal droplets deposit, as illustrated in Fig.1. This actually requires the right chemical composition of the suspension.…”

Section: Introductionmentioning

confidence: 51%

Remote-controlled deposit of superparamagnetic colloidal droplets

et al. 2018

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Evaporation of sessile droplets is a way to organize suspended particles and create surface coating. Many studies have demonstrated that suspensions with various composition can give rise to qualitatively different dried patterns, often by focusing on the radial density profile of deposited particles. We demonstrate that a single suspension of superparamagnetic colloids can give rise to several dried patterns thanks to an external magnetic field applied during the evaporation process. We show the various patterns obtained with zero, constant, rotating and oscillating magnetic fields, and evidence the continuous control given by the intensity of a constant magnetic field. We also show this magnetic control has a substantial effect on the morphological details of the deposits.FIG. 1. Four deposits (four corners of the drop) obtained with different magnetic fields (null, homogeneous, rotating and oscillating fields, amplitude of non-zero magnetic fields are 22.5 G). Each picture has been numerically colorized, cropped as corner and positioned according to the corresponding field condition. The bottom picture is a zoom on the squared area. The global surface density of particles does not change very much. However, the morphological details of the deposit are radically different from one field to the other.

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Section: Introductionmentioning

confidence: 51%

Remote-controlled deposit of superparamagnetic colloidal droplets

et al. 2018

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“…When submitted to a magnetic field, the magnetic energy per particle is much larger than the thermal energy and thus the magnetic forces can overcome Brownian motion to get the particles aligned into columns along the direction of the magnetic field (Figure c and Figure S5, Supporting Information) . This is observed both for the γ‐Fe 2 O 3 /silica and ε‐Fe 2 O 3 /silica particles.…”

Section: Resultsmentioning

confidence: 93%

Alignment under Magnetic Field of Mixed Fe₂O₃/SiO₂Colloidal Mesoporous Particles Induced by Shape Anisotropy

Fornasieri

Bleuzen

et al. 2016

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When using the bottom-up approach with anisotropic building-blocks, an important goal is to find simple methods to elaborate nanocomposite materials with a truly macroscopic anisotropy. Here, micrometer size colloidal mesoporous particles with a highly anisotropic rod-like shape (aspect ratio ≈ 10) have been fabricated from silica (SiO ) and iron oxide (Fe O ). When dispersed in a solvent, these particles can be easily oriented using a magnetic field (≈200 mT). A macroscopic orientation of the particles is achieved, with their long axis parallel to the field, due to the shape anisotropy of the magnetic component of the particles. The iron oxide nanocrystals are confined inside the porosity and they form columns in the nanochannels. Two different polymorphs of Fe O iron oxide have been stabilized, the superparamagnetic γ-phase and the rarest multiferroic ε-phase. The phase transformation between these two polymorphs occurs around 900 °C. Because growth occurs under confinement, a preferred crystallographic orientation of iron oxide is obtained, and structural relationships between the two polymorphs are revealed. These findings open completely new possibilities for the design of macroscopically oriented mesoporous nanocomposites, using such strongly anisotropic Fe O /silica particles. Moreover, in the case of the ε-phase, nanocomposites with original anisotropic magnetic properties are in view.

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“…where θ is the angle between the external field and the line joining the sphere centres [43,44]. Interestingly, a dual application of electric and magnetic fields on superparamagnetic particles allows the formation of birectional chains, colloidal networks and crystals by modulating the electric field and by keeping uniform the magnetic field [45].…”

Section: Magnetic Forcesmentioning

confidence: 99%

Nonisotropic Self‐Assembly of Nanoparticles: From Compact Packing to Functional Aggregates

et al. 2018

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Quantum strongly correlated systems that exhibit interesting features in condensed matter physics often need an unachievable temperature or pressure range in classical materials. One solution is to introduce a scaling factor, namely, the lattice parameter. Synthetic heterostructures named superlattices or supracrystals are synthesized by the assembling of colloidal atoms. These include semiconductors, metals, and insulators for the exploitation of their unique properties. Most of them are currently limited to dense packing. However, some of desired properties need to adjust the colloidal atoms neighboring number. Here, the current state of research in nondense packing is summarized, discussing the benefits, outlining possible scenarios and methodologies, describing examples reported in the literature, briefly discussing the challenges, and offering preliminary conclusions. Penetrating such new and intriguing research fields demands a multidisciplinary approach accounting for the coupling of statistic physics, solid state and quantum physics, chemistry, computational science, and mathematics. Standard interactions between colloidal atoms and emerging fields, such as the use of Casimir forces, are reported. In particular, the focus is on the novelty of patchy colloidal atoms to meet this challenge.

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Predicting the Self‐Assembly of Superparamagnetic Colloids under Magnetic Fields

Cited by 109 publications

References 80 publications

Remote-controlled deposit of superparamagnetic colloidal droplets

Remote-controlled deposit of superparamagnetic colloidal droplets

Alignment under Magnetic Field of Mixed Fe₂O₃/SiO₂Colloidal Mesoporous Particles Induced by Shape Anisotropy

Nonisotropic Self‐Assembly of Nanoparticles: From Compact Packing to Functional Aggregates

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Predicting the Self‐Assembly of Superparamagnetic Colloids under Magnetic Fields

Cited by 109 publications

References 80 publications

Remote-controlled deposit of superparamagnetic colloidal droplets

Remote-controlled deposit of superparamagnetic colloidal droplets

Alignment under Magnetic Field of Mixed Fe2O3/SiO2Colloidal Mesoporous Particles Induced by Shape Anisotropy

Nonisotropic Self‐Assembly of Nanoparticles: From Compact Packing to Functional Aggregates

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Alignment under Magnetic Field of Mixed Fe₂O₃/SiO₂Colloidal Mesoporous Particles Induced by Shape Anisotropy