Creation of liquid-crystal periodic zigzags by surface treatment and thermal annealing

Ryu, Seong Ho; Gim, Min-Jun; Jeong, Yong‐Hoon; Shin, Tae Joo; Ahn, Hyungju; Yoon, Dong Ki

doi:10.1039/c5sm01989c

Cited by 13 publications

(15 citation statements)

References 41 publications

(40 reference statements)

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“…The cooling rate is another parameter that can determine the crystallization path of soft materials. , To investigate its influence on Au@L crystallization and to determine the optimal cooling rate, we prepared samples using 30 (Au@L 30 ), 3 (Au@L 3 ), and 0.5 (Au@L 0.5 ) °C/min cooling rates. In all cases, samples were heated at a rate of 30 °C/min, since the heating kinetics does not affect the quality of the assemblies.…”

Section: Resultsmentioning

confidence: 99%

Understanding and Controlling the Crystallization Process in Reconfigurable Plasmonic Superlattices

et al. 2021

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The crystallization of nanomaterials is a primary source of solid-state, photonic structures. Thus, a detailed understanding of this process is of paramount importance for the successful application of photonic nanomaterials in emerging optoelectronic technologies. While colloidal crystallization has been thoroughly studied, for example, with advanced in situ electron microscopy methods, the noncolloidal crystallization (freezing) of nanoparticles (NPs) remains so far unexplored. To fill this gap, in this work, we present proof-of-principle experiments decoding a crystallization of reconfigurable assemblies of NPs at a solid state. The chosen material corresponds to an excellent testing bed, as it enables both in situ and ex situ investigation using X-ray diffraction (XRD), transmission electron microscopy (TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), atomic force microscopy (AFM), and optical spectroscopy in visible and ultraviolet range (UV–vis) techniques. In particular, ensemble measurements with small-angle XRD highlighted the dependence of the correlation length in the NPs assemblies on the number of heating/cooling cycles and the rate of cooling. Ex situ TEM imaging further supported these results by revealing a dependence of domain size and structure on the sample preparation route and by showing we can control the domain size over 2 orders of magnitude. The application of HAADF-STEM tomography, combined with in situ thermal control, provided three-dimensional single-particle level information on the positional order evolution within assemblies. This combination of real and reciprocal space provides insightful information on the anisotropic, reversibly reconfigurable assemblies of NPs. TEM measurements also highlighted the importance of interfaces in the polydomain structure of nanoparticle solids, allowing us to understand experimentally observed differences in UV–vis extinction spectra of the differently prepared crystallites. Overall, the obtained results show that the combination of in situ heating HAADF-STEM tomography with XRD and ex situ TEM techniques is a powerful approach to study nanoparticle freezing processes and to reveal the crucial impact of disorder in the solid-state aggregates of NPs on their plasmonic properties.

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Section: Resultsmentioning

confidence: 99%

Understanding and Controlling the Crystallization Process in Reconfigurable Plasmonic Superlattices

et al. 2021

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“…When oblate CLC droplets are heated up to isotropic, the helical structure gradually unwinds with an increase in helical pitch, thus showing a redshift color change from blue to green, [ 30,54 ] as shown in Figure S5, Supporting Information. In addition to helical pitch, the wavelength of reflected light could also be adjusted by the angle of incident light and the color of the films changes when the films are viewed at different angles of 0°, 45°, and grazing incident, [ 55 ] as shown in Figure 3d and Figure S6, Supporting Information.…”

Section: Figurementioning

confidence: 99%

“…The developed systems based on oblate CLC droplets are unique and could demonstrate synergetic color and shape responses. Compared to various color changing systems based on CLCs, [ 26–28,32,55–57 ] our systems have several advantages: 1) A new strategy to achieve large selective Bragg reflection in CLC droplets. CLC droplets or shells could show macroscopic color that is visible by naked eyes only when they are large enough on the scale of hundreds of micrometers.…”

Section: Figurementioning

confidence: 99%

3D‐Printed Biomimetic Systems with Synergetic Color and Shape Responses Based on Oblate Cholesteric Liquid Crystal Droplets

Yang

Ruan

et al. 2021

Advanced Materials

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Living organisms in nature have amazing control over their color, shape, and morphology in response to environmental stimuli for camouflage, communication, or reproduction. Inspired by the camouflage of the octopus via the elongation or contraction of its pigment cells, oblate cholesteric liquid crystal droplets are dispersed in a polymer matrix, serving as the role of pigment cells and showing structural color due to selective Bragg reflection by their periodic helical structure. The color of 3D‐printed biomimetic systems can be tuned by changing the helical pitch via the chiral dopant concentration or temperature. When the oblate liquid crystal droplets are heated up to isotropic, the opaque and colored biomimetic systems become transparent and colorless. Meanwhile, the isotropic liquid crystal droplets tend to become spherical, causing volume contraction along the film plane and volume dilation in the perpendicular direction. The internal strain combined with the gradient distribution of the oblate isotropic liquid crystal droplets result in corresponding shape transformations. The camouflage of a biomimetic octopus and the blossom of a biomimetic flower, both of which show synergetic color and shape responses, are demonstrated to inspire the design of functional materials and intelligent devices.

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“…[13] In that work, the orientation of the columnar structures could not be controlled in a large area because of the lack of long range order, [14] although there are reported some successes with columnar structures of common discotic liquid crystals. To control the orientation of ambipolar discotic molecules, [15][16][17][18][19] conventional alignment methods such as surface treatment, [20][21][22] mechanical shearing, [23][24][25] and rubbed polymer layer [26,27] cannot uniaxially guide the columnar structures. To solve this problem, nanoconfinement [28][29][30][31][32] has emerged as a powerful tool, and is useful to generate well-oriented supramolecular structures in various kinds of organic materials.…”

Section: Introductionmentioning

confidence: 99%

Manipulation of Supramolecular Columnar Structures of H‐Bonded Donor‐Acceptor Units through Geometrical Nanoconfinement

et al. 2019

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Ambipolar organic semiconductors are considered promising for organic electronics because of their interesting electric properties. Many hurdles remain yet to be overcome before they can be used for practical applications, especially because their orientation is hard to control. We demonstrate a method to control the orientation of columnar structures based on a hydrogen (H)‐bonded donor‐acceptor complex between a star‐shaped tris(triazolyl)triazine and triphenylene‐containing benzoic acid, using physicochemical nanoconfinement. The molecular configuration and supramolecular columnar assemblies in a one‐dimensional porous anodic aluminium oxide (AAO) film were dramatically modulated by controlling the pore‐size and by chemical modification of the inner surface of the porous AAO film. In situ experiments using grazing‐incidence X‐ray diffraction (GIXRD) were carried out to investigate the structural evolution produced at the nanometer scale by varying physicochemical conditions. The resulting highly ordered nanostructures may open a new pathway to effectively control the alignment of liquid crystal ambipolar semiconductors.

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Creation of liquid-crystal periodic zigzags by surface treatment and thermal annealing

Cited by 13 publications

References 41 publications

Understanding and Controlling the Crystallization Process in Reconfigurable Plasmonic Superlattices

Understanding and Controlling the Crystallization Process in Reconfigurable Plasmonic Superlattices

3D‐Printed Biomimetic Systems with Synergetic Color and Shape Responses Based on Oblate Cholesteric Liquid Crystal Droplets

Manipulation of Supramolecular Columnar Structures of H‐Bonded Donor‐Acceptor Units through Geometrical Nanoconfinement

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