Self-assembly of spherical colloidal particles with off-centered magnetic dipoles

Abrikosov, Alexei I.; Sacanna, Stefano; Philipse, Albert P.; Linse, Per

doi:10.1039/c3sm27128e

Cited by 43 publications

(43 citation statements)

References 18 publications

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“…Each bifunctional particle is comprised of a 300 nm-wide hematite cube partially embedded in the surface of a 2 µm-diameter sphere made of 3-methacryloxypropyl trimethoxysilane (TPM) [11][12][13][14]. The bright-field microscope image in Figure 1(b) shows a typical particle with its cube visible on the left side.…”

Section: Light-activated Swimmersmentioning

confidence: 99%

Trochoidal trajectories of self-propelled Janus particles in a diverging laser beam

et al. 2016

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We describe colloidal Janus particles with metallic and dielectric faces that swim vigorously when illuminated by defocused optical tweezers without consuming any chemical fuel. Rather than wandering randomly, these optically-activated colloidal swimmers circulate back and forth through the beam of light, tracing out sinuous rosette patterns. We propose a model for this mode of light-activated transport that accounts for the observed behavior through a combination of self-thermophoresis and optically-induced torque. In the deterministic limit, this model yields trajectories that resemble rosette curves known as hypotrochoids.

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Section: Light-activated Swimmersmentioning

confidence: 99%

Trochoidal trajectories of self-propelled Janus particles in a diverging laser beam

et al. 2016

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“…21,23 However, the precise magnitude and orientation of the magnetic moment are still uncertain and the subject of on-going study. 21,44 With respect to the electrical double layer repulsion between the hematite and silica superballs it has to be realized that the accurate values of surface potentials or surface charge densities are difficult to obtain and zeta potentials cannot readily be converted into surface charge densities. For further discussion on this point we refer to ref.…”

Section: Cube Propertiesmentioning

confidence: 99%

“…21,23,44 However, once in the sediment the surface charge is not high enough to compensate the gravitational compression causing kinetic arrest and an inability for neighboring crystals to reorient.…”

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Self-assembly of colloidal hematite cubes: a microradian X-ray diffraction exploration of sedimentary crystals

et al. 2013

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The structure of spontaneously formed crystals in the sediments of colloidal hematite (a-Fe 2 O 3 ) cubes is studied using microradian X-ray diffraction. The hematite cubes possess a superball shape and a permanent magnetic dipole moment, both influencing the self-assembly behaviour and inducing directionality in different ways. To control the inter-cube interactions, the cubes were dispersed in different solvents and/or coated with a silica layer and allowed to form sediments under the simultaneous effect of the gravitational field and an applied magnetic field. The microradian X-ray diffraction revealed that changing the double layer repulsion that opposes the magnetic and van der Waals attractions can induce short to long-range ordering in the fast sedimenting systems of the cubes. The presence of an external magnetic field during sedimentation induced the formation of a single crystal with long-range order that showed different symmetries, rectangular or hexagonal, close to the fluid-solid interface. The identified 3D crystal structure of both was found to have a body centred monoclinic lattice periodicity that rotates deeper in the sediment due to gravitational compression. This experimental structure differs from the expected crystal lattices determined by simulations and is most likely due to the effects of long-range repulsion and dipole-dipole interactions present here.

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“…31 However, there was uncertainty in the direction of the dipole moment within the magnetic cube in this experimental system. 35 It was most likely that the direction of the dipole was not parallel to the radial shift vector to the position of the dipole. 35 We introduced an additional model parameter θ, denoting the angle at which the direction of the point-dipole is inclined to the radial shift vector (see Fig.…”

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“…31,33 Having drawn motivation from these research activities, a number of computational studies have focused on spherical magnetic colloids with an additional anisotropy attribute in terms of an off-centered point-dipole. 16,34,35 We considered charge-stabilized colloidal magnetic particles, which included a permanent point-dipole shifted away from the center, 16 closely resembling those synthesized using a single-domain hematite cube inclusion underneath the surface of organopolymer spheres. 31 However, there was uncertainty in the direction of the dipole moment within the magnetic cube in this experimental system.…”

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Programming hierarchical self-assembly of colloids: matching stability and accessibility

Morphew

Chakrabarti

2018

Nanoscale

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Encoding hierarchical self-assembly in colloidal building blocks is a promising bottom-up route to high-level structural complexity often observed in biological materials. However, harnessing this promise faces the grand challenge of bridging hierarchies of multiple length-and time-scales, associated with structure and dynamics respectively along the self-assembly pathway. Here we report on a case study, which examines the kinetic accessibility of a series of hollow spherical structures with a two-level structural hierarchy self-assembled from charge-stabilized colloidal magnetic particles. By means of a variety of computational methods, we find that for a staged assembly pathway, the structure, which derives the strongest energetic stability from the first stage of assembly and the weakest from the second stage, is most kinetically accessible. Such a striking correspondence between energetics and kinetics for optimal design principles should have general implications for programming hierarchical self-assembly pathways for nano-and micro-particles, while matching stability and accessibility.Self-assembly of colloidal particles offers tremendous opportunities for fabricating three-dimensional structures in a bottom-up approach due to the scope for tuning the interparticle interactions.1,2 Recent advances in the synthesis of complex colloidal particles have made a wide variety of nanoand micro-scale building blocks available. Many of these colloidal building blocks involve anisotropic interparticle interactions, often due to either anisotropic shape or heterogeneous surface chemistry. 2-5 These novel colloidal particles offer rich avenues for programming colloidal self-assembly.6,7Hierarchical self-assembly of nano-and micro-particles is emerging as an attractive route to structural organization at a higher level, spanning multiple length scales. 8,9 Notably, the hierarchical self-assembly of mono-disperse colloidal octapodshaped nanocrystals resulted in a three-dimensional superlattice via the formation of linear chains of interlocked octapods. 10 The assembly of binary and ternary patchy nanoparticles produced supracolloidal ordered structures in a hierarchical scheme. 11 The 'patchiness' of colloidal triblock spherical particles was exploited to encode staged self-assembly triggered by stepwise changes of the ionic strength of the medium. 12 A computational study demonstrated an alternative scheme for patchiness without engineered surfaces en route to a variety of complex superstructures via hierarchical selfassembly. 13 A theoretical analysis was presented for programming self-assembly of octopus nanoparticles, which themselves may be self-assembled, into a target nanostructure.

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Self-assembly of spherical colloidal particles with off-centered magnetic dipoles

Cited by 43 publications

References 18 publications

Trochoidal trajectories of self-propelled Janus particles in a diverging laser beam

Trochoidal trajectories of self-propelled Janus particles in a diverging laser beam

Self-assembly of colloidal hematite cubes: a microradian X-ray diffraction exploration of sedimentary crystals

Programming hierarchical self-assembly of colloids: matching stability and accessibility

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