Anisotropic photonic crystal building blocks: colloids tuned from mushroom-caps to dimers

Fung, E. Y.; Muangnapoh, Kullachate; Watson, Chekesha M. Liddell

doi:10.1039/c2jm00129b

Cited by 25 publications

(16 citation statements)

References 39 publications

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“…In recent years, a range of silica and polymer nonspherical particle shapes have been prepared with narrow size distribution and in suffi cient quantity (i.e., for colloidal crystallization): ellipsoid; dimer (two adjacent or fused spheres); spherocylinder; peanut; blood cell; football; boomerang; hex nut; trapezoidal-and pentagonal prisms, for example. [2][3][4][5] In addition, thermodynamic simulations predict diverse liquid crystal, plastic crystal and degenerate crystal phases as well as a wide range of crystallographic groups from faceted space fi lling colloidal polyhedra. [6][7][8][9][10] The diverse structures from anisotropic particles hold uncharted photonic properties inaccessible from the commonly available spherical colloidal building blocks.…”

Section: Doi: 101002/adom201400266mentioning

confidence: 99%

Anisometric Colloidal Fullerene Rod and Platelet Solvates with Enhanced Photoluminescence

Penterman

Singh

Zipfel

et al. 2014

Advanced Optical Materials

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wileyonlinelibrary.com COMMUNICATIONsubwavelength imaging (superlens). [ 12,13 ] In addition, doping sphere-based photonic crystals with rare earths, lanthanides, organic dyes and quantum dots has established properties such as suppression or enhancement of spontaneous emission and photonic crystal lasing due to multiple refl ections and high density of states at the photonic band gap edges. [14][15][16] Only a handful of experimental reports address uniform nonspherical colloidal building blocks (i.e., size range between 400 nm and 1.5 micrometers for photonic crystals in the visible and nearinfrared regimes) with an active optical functionality (i.e., luminescence) at the single particle level.The present work develops fullerene microcrystals as a new materials platform, suitable for 'active' light emitting elements in colloid-based photonic crystals. The materials support singlet excited states that tend to be self-trapped by localized lattice deformation (i.e., Jahn-Teller distortion) and recombine to produce a characteristic red photoluminescence (PL). [17][18][19][20] These high refractive index and transparent building blocks (λ > 560 nm) may also support photonic band gaps in direct structures as compared to the common silica and polymer sphere-based structures which must be backfi lled with semiconductors such as Si and GaAs. [ 11 ] Fullerene molecular crystals have previously been synthesized in a variety of bulk to mesoscale forms including thick and thin fi lms, [ 21 ] wire arrays, [ 22 ] whiskers [ 23 ] and platelets. [ 24 ] Micrometer and sub-micrometer crystals have also been prepared with anisotropic morphology using solution-based techniques such as precipitation at the interface between immiscible liquids (LLIP, liquid-liquid interfacial precipitation), [24][25][26] and evaporation-assisted growth from drops on a substrate. [27][28][29][30] Control of size and shape dispersity with these methods is still lacking. In contrast, microcrystal growth in emulsifi ed solvent-nonsolvent mixtures (co-solvent precipitation) has yielded colloidal particles with tunable shapes, crystal structure and monodispersity. [31][32][33][34] Droplet shrinkage over time in miscible liquids causes local supersaturation of the fullerenes and leads to particle nucleation. The solvent properties (i.e., molecular shape, fullerene solubility, dipole moment, miscibility, interdiffusion rate, etc.), solvent-antisolvent ratio, concentration, temperature and mixing conditions determine the colloidal chemistry and morphology. [31][32][33][34][35] For example, crystallization of C 60 with CS 2 in 2-propanol resulted in bipyramidal-shaped particles, C 70 crystallized with CS 2 in 1-propanol produced rugby ball shapes as well as rhombic dodecahedra, and C 70 with mesitylene in 2-propanol solution produced cubes. [ 31,32 ] Here, we report the synthesis of shape diverse and monodisperse microcrystal solvates using co-solvent precipitation with C 60 and C 70 fullerene-methylbenzene solutions in 2-propanol as a poor solvent. The photol...

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Section: Doi: 101002/adom201400266mentioning

confidence: 99%

Anisometric Colloidal Fullerene Rod and Platelet Solvates with Enhanced Photoluminescence

Penterman

Singh

Zipfel

et al. 2014

Advanced Optical Materials

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“…Anisotropic colloids have recently attracted growing interest in the soft matter community. 1,2 Their phase behavior and selfassembly have been investigated theoretically and experimentally for rod-like, [2][3][4][5] ellipsoidal, [6][7][8][9][10][11][12] dumbbell-shaped, [13][14][15][16] bowl-shaped, [17][18][19][20][21] cubic, 9,22 and polyhedral particles. 23,24 However, despite the increasing number of approaches for synthesizing well-defined non-spherical colloids with a large range of particle shapes in the last decade, attempts to synthesize responsive anisotropic particles are still sparse.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic responsive microgels with tuneable shape and interactions

et al. 2015

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Highly monodisperse polystyrene/poly(N-isopropylmethacrylamide) (PS-PNIPMAM) core-shell composite microgels were synthesized and further nanoengineered in either ellipsoidal, faceted or bowl-shaped particles. Beside their anisotropy in shape, the microgel design enables an exquisite control of the particle conformation, size and interactions from swollen and hydrophilic to collapsed and hydrophobic using temperature as an external control variable. The post-processing procedures and the characterization of the different particles are first presented. Their potential as model systems for the investigation of the effects of anisotropic shape and interactions on the phase behavior is further demonstrated. Finally, the self-assembly of bowl-shaped composite microgel particles is discussed, where the temperature and an external AC electric field are employed to control the interactions from repulsive to attractive and from soft repulsive to dipolar, respectively.

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“…The particle model, shown in Figure 1, is used to represent the features of real mushroom cap-shaped (MCS) colloidal particles [57][58][59][60][61] . Under strong geometrical confinement, MCS particles exhibit a very rich phase behaviour due to their anisotropic shape and lack of centrosymmetry 58,62 .…”

Section: Introductionmentioning

confidence: 99%

Phase behaviour and gravity-directed self assembly of hard convex spherical caps

McBride

Avendaño

2017

Soft Matter

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We investigate the phase behaviour and self-assembly of convex spherical caps using Monte Carlo simulations. This model is used to represent the main features observed in experimental colloidal particles with mushroom-cap shape [Riley et al., Langmuir, 2010, 26, 1648. The geometry of this non-centrosymmetric convex model is fully characterized by the aspect ratio χ * defined as the spherical cap height to diameter ratio. We use NPT Monte Carlo simulations combined with free energy calculations to determine the most stable crystal structures and the phase behaviour of convex spherical caps with different aspect ratios. We find a variety of crystal structures at each aspect ratio, including plastic and dimer-based crystals; small differences in chemical potential between the structures with similar morphology suggest that convex spherical caps have the tendency to form polycrystalline phases rather than crystallising into a single uniform structure. With the exception of plastic crystals observed at large aspect ratios (χ * > 0.75), crystallisation kinetics seem to be too slow, hindering the spontaneous formation of ordered structures. As an alternative, we also present a study of directing the self-assembly of convex spherical caps via sedimentation onto solid substrates. This study contributes to show how small changes to particle shape can significantly alter the self-assembly of crystal structures, and how a simple gravity field and a template can substantially enhance the process.

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Anisotropic photonic crystal building blocks: colloids tuned from mushroom-caps to dimers

Cited by 25 publications

References 39 publications

Anisometric Colloidal Fullerene Rod and Platelet Solvates with Enhanced Photoluminescence

Anisometric Colloidal Fullerene Rod and Platelet Solvates with Enhanced Photoluminescence

Anisotropic responsive microgels with tuneable shape and interactions

Phase behaviour and gravity-directed self assembly of hard convex spherical caps

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