Reconfigurable colloids

Solomon, Michael J.

doi:10.1038/464496a

Cited by 19 publications

(15 citation statements)

References 10 publications

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“…[ 7 ] Further, the orientational alignment of the anisotropic building blocks is also important for new forms of matter, such as metamaterials [ 1 , 8 ] and reconfi gurable colloids. [ 9 ] Spheroids are simple anisotropic building blocks that may adopt both positional and orientational order in crystal structures. A practical advantage of using spheroids for experimental studies is their convenient production via syntheses based on the solidifi cation of liquid droplets.…”

Section: Introductionmentioning

confidence: 99%

Liquid Crystal Order in Colloidal Suspensions of Spheroidal Particles by Direct Current Electric Field Assembly

Shah

Kang

Kohlstedt

et al. 2012

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DC electric fields are used to produce colloidal assemblies with orientational and layered positional order from a dilute suspension of spheroidal particles. These 3D assemblies, which can be visualized in situ by confocal microscopy, are achieved in short time spans (t < 1 h) by the application of a constant voltage across the capacitor-like device. This method yields denser and more ordered assemblies than had been previously reported with other assembly methods. Structures with a high degree of orientational order as well as layered positional order normal to the electrode surface are observed. These colloidal structures are explained as a consequence of electrophoretic deposition and field-assisted assembly. The interplay between the deposition rate and the rotational Brownian motion is found to be critical for the optimal ordering, which occurs when these rates, as quantified by the Peclet number, are of order one. The results suggest that the mechanism leading to ordering is equilibrium self-assembly but with kinetics dramatically accelerated by the application of the DC electric field. Finally, the crystalline symmetry of the densest structure formed is determined and compared with previously studied spheroidal assemblies.

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Section: Introductionmentioning

confidence: 99%

Liquid Crystal Order in Colloidal Suspensions of Spheroidal Particles by Direct Current Electric Field Assembly

Shah

Kang

Kohlstedt

et al. 2012

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confidence: 99%

“…This system is unique in that it allows access to a regime wherein several interparticle forces are of comparable strength, leading to an unusual example of a one-dimensional superlattice of inorganic disc-like nanostructures that is stable in solution. Furthermore, these columnar assemblies are highly reconfigurable through modification of several intensive and extensive variables, providing a means to create tunable stimuli-responsive materials (18,25).Depletion forces are purely entropic in nature and arise when small, nonadsorbing molecules, such as surfactants, are added to a colloidal solution of particles (26). Two large particles of radius R immersed in a dispersion of small particles (depletants) with radius r possess an exclusion layer whose thickness is equal to r. As the surfaces of the large particles reach a separation smaller than the diameter of the depletant (2r), their exclusion layers begin to overlap and the total volume available to the depletants is increased, thereby decreasing the free energy of the system by…”

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confidence: 99%

Assembly of reconfigurable one-dimensional colloidal superlattices due to a synergy of fundamental nanoscale forces

Young

Jones

Zhang

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

151

167

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We report that triangular gold nanoprisms in the presence of attractive depletion forces and repulsive electrostatic forces assemble into equilibrium one-dimensional lamellar crystals in solution with interparticle spacings greater than four times the thickness of the nanoprisms. Experimental and theoretical studies reveal that the anomalously large d spacings of the lamellar superlattices are due to a balance between depletion and electrostatic interactions, both of which arise from the surfactant cetyltrimethylammonium bromide. The effects of surfactant concentration, temperature, ionic strength of the solution, and prism edge length on the lattice parameters have been investigated and provide a variety of tools for in situ modulation of these colloidal superstructures. Additionally, we demonstrate a purification procedure based on our observations that can be used to efficiently separate triangular nanoprisms from spherical nanoparticles formed concomitantly during their synthesis.anisotropic | tunable | small angle X-ray scattering | depletion interaction T he ability to form ensembles of inorganic nanoparticles with a high degree of control has become one of the main areas of focus in nanoscience research (1). This interest stems from the fact that nanocrystal superlattices often exhibit electronic (2), optical (3), and magnetic (4) properties that are distinct from both the corresponding individual particles and the bulk solid as a result of the interactions between the excitons, surface plasmons, or magnetic moments of the assembled particles (5). Superlattices composed of spherical building blocks have been extensively studied, and researchers now have the ability to synthesize a wide variety of structures (6). However, as new techniques are developed to synthesize high-quality anisotropic nanoparticles with new physical properties that cannot be obtained with spheres alone, researchers are increasingly interested in the rich assembly behavior of particles with reduced symmetry (7-9). Indeed, periodic arrays of these anisotropic building blocks have been shown to possess unique collective properties with applications in various fields including plasmonics (10) and photonics (11). However, to take full advantage of these collective properties, it is necessary to understand the relationship between the architectural parameters of the ensemble and the emergent physical properties. For this purpose, it is crucial to be able to "engineer" the various interactions that exist between nanoparticle building blocks to produce a desired structure (12, 13). The assembly of nanocrystals into ordered arrays can be induced via the manipulation of interparticle interactions including van der Waals (14), electrostatic (15), entropic (16-21), and through highly specific biological interactions (22-24). Herein, we report the assembly of colloidal triangular gold nanoprisms protected by a cetyltrimethylammonium bromide (CTAB) bilayer in a solution of CTAB micelles into highly ordered 1D crystals with unexpected structural f...

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“…Such complex unit cells have applications in advanced optical materials 7. Further, the orientational alignment of the anisotropic building blocks is also important for new forms of matter, such as metamaterials1, 8 and reconfigurable colloids 9. Spheroids are simple anisotropic building blocks that may adopt both positional and orientational order in crystal structures.…”

Section: Introductionmentioning

confidence: 99%

Copper Ion Enhanced Synthesis of Nanostructured Cobalt Oxide Catalyst for Oxidation of Methane

Feng

Zheng

2012

ChemCatChem

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Cu can help Co3O4: The Cu2+ ions can improve the growth of a onedimensional Co3O4 catalyst on stainless steel mesh by facilitating the nucleation process. With higher mass loading and coverage density, the 1 D nanostructured Co3O4 grown with Cu2+ ions addition has larger catalytic surface area per unit area of support and, hence, exhibits higher catalytic activity for CH4 oxidation than the Co3O4 grown without Cu2+ added.

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Reconfigurable colloids

Cited by 19 publications

References 10 publications

Liquid Crystal Order in Colloidal Suspensions of Spheroidal Particles by Direct Current Electric Field Assembly

Liquid Crystal Order in Colloidal Suspensions of Spheroidal Particles by Direct Current Electric Field Assembly

Assembly of reconfigurable one-dimensional colloidal superlattices due to a synergy of fundamental nanoscale forces

Copper Ion Enhanced Synthesis of Nanostructured Cobalt Oxide Catalyst for Oxidation of Methane

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