Iridescence in nematics: Photonic liquid crystals of nanoplates in absence of long-range periodicity

Photonic materials with positionally ordered structure can interact strongly with light to produce brilliant structural colors. Here, we found that the nonperiodic nematic liquid crystals of nanoplates can also display structural color with only significant orientational order. Owing to the loose stacking of the nematic nanodiscs, such colloidal dispersion is able to reflect a broad-spectrum wavelength, of which the reflection color can be further enhanced by adding carbon nanoparticles to reduce background scattering. Upon the addition of electrolytes, such vivid colors of nematic dispersion can be fine-tuned via electrostatic forces. Furthermore, we took advantage of the fluidity of the nematic structure to create a variety of colorful arts. It was expected that the concept of implanting nematic features in photonic structure of lyotropic nanoparticles may open opportunities for developing advanced photonic materials for display, sensing, and art applications.

Download Full-text

Enhancing the brightness and saturation of noniridescent structural colors by optimizing the grain size

Nanoscale Advances ◽

10.1039/d0na00609b ◽

2020 ◽

Vol 2 (10) ◽

pp. 4581-4590

Author(s):

Ning Sun ◽

Xianglei Liu ◽

Yan Liu ◽

Rui Zhao ◽

Zhengzheng Xu ◽

...

Keyword(s):

Grain Size ◽

Photonic Crystal ◽

Domain Size ◽

Structural Color ◽

Ordered Structure ◽

High Brightness ◽

Structural Colors

A non-iridescent structural color with high brightness and saturation is obtained by adjusting the domain size of the ordered structure of the photonic crystal.

Download Full-text

Diffusionless transformation of soft cubic superstructure from amorphous to simple cubic and body-centered cubic phases

Nature Communications ◽

10.1038/s41467-021-23631-w ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Jie Liu ◽

Wenzhe Liu ◽

Bo Guan ◽

Bo Wang ◽

Lei Shi ◽

...

Keyword(s):

Liquid Crystals ◽

X Ray Diffraction ◽

Photonic Materials ◽

Simple Cubic ◽

Cubic Phases ◽

Transmission Electron ◽

Phase Liquid ◽

Blue Phase ◽

Blue Phases ◽

Temperature Window

AbstractIn a narrow temperature window in going from the isotropic to highly chiral orders, cholesteric liquid crystals exhibit so-called blue phases, consisting of different morphologies of long, space-filling double twisted cylinders. Those of cubic spatial symmetry have attracted considerable attention in recent years as templates for soft photonic materials. The latter often requires the creation of monodomains of predefined orientation and size, but their engineering is complicated by a lack of comprehensive understanding of how blue phases nucleate and transform into each other at a submicrometer length scale. In this work, we accomplish this by intercepting nucleation processes at intermediate stages with fast cross-linking of a stabilizing polymer matrix. We reveal using transmission electron microscopy, synchrotron small-angle X-ray diffraction, and angle-resolved microspectroscopy that the grid of double-twisted cylinders undergoes highly coordinated, diffusionless transformations. In light of our findings, the implementation of several applications is discussed, such as temperature-switchable QR codes, micro-area lasing, and fabrication of blue phase liquid crystals with large domain sizes.

Download Full-text

Ion conformation and orientational order in a dicationic ionic liquid crystal studied by solid-state nuclear magnetic resonance spectroscopy

Scientific Reports ◽

10.1038/s41598-021-85021-y ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Debashis Majhi ◽

Sergey V. Dvinskikh

Keyword(s):

Ionic Liquid ◽

Ionic Liquids ◽

Liquid Crystals ◽

Bond Order ◽

Van Der Waals ◽

Orientational Order ◽

Smectic Phase ◽

Side Chains ◽

Dicationic Ionic Liquid ◽

Ionic Liquid Crystals

AbstractIonic liquids crystals belong to a special class of ionic liquids that exhibit thermotropic liquid-crystalline behavior. Recently, dicationic ionic liquid crystals have been reported with a cation containing two single-charged ions covalently linked by a spacer. In ionic liquid crystals, electrostatic and hydrogen bonding interactions in ionic sublayer and van der Waals interaction in hydrophobic domains are the main forces contributing to the mesophase stabilization and determining the molecular orientational order and conformation. How these properties in dicationic materials are compared to those in conventional monocationic analogs? We address this question using a combination of advanced NMR methods and DFT analysis. Dicationic salt 3,3′-(1,6-hexanediyl)bis(1-dodecylimidazolium)dibromide was studied. Local bond order parameters of flexible alkyl side chains, linker chain, and alignment of rigid polar groups were analyzed. The dynamic spacer effectively “decouples” the motion of two ionic moieties. Hence, local order and alignment in dicationic mesophase were similar to those in analogous single-chain monocationic salts. Bond order parameters in the side chains in the dicationic smectic phase were found consistently lower compared to double-chain monocationic analogs, suggesting decreasing contribution of van der Waals forces. Overall dication reorientation in the smectic phase was characterized by low values of orientational order parameter S. With increased interaction energy in the polar domain the layered structure is stabilized despite less ordered dications. The results emphasized the trends in the orientational order in ionic liquid crystals and contributed to a better understanding of interparticle interactions driving smectic assembly in this and analogous ionic mesogens.

Download Full-text

Line broadening in the electron resonance spectra of spin probes dissolved in anisotropic media: the effect of nuclear spin quantization

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1977.0023 ◽

1977 ◽

Vol 353 (1672) ◽

pp. 87-102 ◽

Cited By ~ 13

Keyword(s):

Liquid Crystal ◽

Liquid Crystals ◽

Nuclear Spin ◽

Dynamic Properties ◽

Orientational Order ◽

Anisotropic Media ◽

Approximate Theory ◽

Spin Probes ◽

Line Broadening ◽

Electron Resonance

The line broadening in the electron resonance spectra of monoradicals dissolved in anisotropic media, such as liquid crystals, provides a valuable probe of both the orientational order and the molecular dynamics. However, the fast-motion relaxation theory employed to extract this information from the linewidths assumes that the nuclear spin is quantized along the direction of the magnetic field. This approximation is only correct when the symmetry axis of a uniaxial liquid crystal is either parallel or perpendicular to the field. We have therefore removed this assumption and have developed a general theory of line broadening valid for all orientations of the liquid crystal. The theory is then used to evaluate the angular dependence of the linewidths and this is compared with the dependence predicted by the approximate theory, for two classes of nitroxide spin probes. These comparisons reveal that for steroidal spin probes the error, introduced by assuming the nuclear spin to be quantized along the field, is confined to the dynamic properties derived from the linewidths. In contrast, significant errors appear in both the dynamic and static properties obtained from an analysis of the linewidth variations for fatty acid spin probes based on the approximate theory. It would seem that the exact theory must be employed to obtain precise information from linewidth investigations of liquid crystals, except when the orientational order is extremely small.

Download Full-text

Orientational order in liquid crystals by combiningH2andC13nuclear magnetic resonance spectroscopy and density functional theory calculations

Physical Review E ◽

10.1103/physreve.82.041702 ◽

2010 ◽

Vol 82 (4) ◽

Cited By ~ 9

Author(s):

Lucia Calucci ◽

Marco Geppi ◽

Alberto Marini ◽

Carlo Alberto Veracini

Keyword(s):

Density Functional Theory ◽

Liquid Crystals ◽

Magnetic Resonance ◽

Magnetic Resonance Spectroscopy ◽

Density Functional ◽

Orientational Order ◽

Density Functional Theory Calculations ◽

Resonance Spectroscopy ◽

Functional Theory

Download Full-text

Maximizing Orientational Order in Polymer-Stabilized Liquid Crystals Using High Magnetic Fields

Macromolecules ◽

10.1021/ma501867f ◽

2015 ◽

Vol 48 (4) ◽

pp. 1002-1008 ◽

Cited By ~ 1

Author(s):

Alexandra Alvarez Fernandez ◽

Masoumeh Keshavarz ◽

Peter C. M. Christianen ◽

Paul H. J. Kouwer

Keyword(s):

Liquid Crystals ◽

Magnetic Fields ◽

Orientational Order ◽

High Magnetic Fields ◽

Polymer Stabilized

Download Full-text

Studies Of Orientational Order Of Some Nematogens By Means Of Raman Scattering Spectroscopy

Zeitschrift für Naturforschung A ◽

10.1515/zna-2004-7-817 ◽

2004 ◽

Vol 59 (7-8) ◽

pp. 510-516 ◽

Cited By ~ 2

Author(s):

Ewa Chrzumnicka ◽

Mirosław Szybowicz ◽

Danuta Bauman

Keyword(s):

Liquid Crystals ◽

Raman Scattering ◽

Orientational Order ◽

Polarized Light ◽

Molecular Structures ◽

Raman Scattering Spectroscopy ◽

Linearly Polarized ◽

Scattering Spectra ◽

Raman Scattering Spectra ◽

Molecular Distribution Function

The orientational behaviour of some liquid crystals with various molecular structures was studied by means of the Raman scattering depolarization method. The Raman scattering spectra of linearly polarized light were recorded as a function of temperature in the nematic phase. On the basis of these spectra the order parameters 〈P2〉 and 〈P4〉 as well as the molecular distribution function were determined. The obtained data were compared with those estimated on the basis of polarized light absorption and emission measurements. The influence of the molecular structure on the orientational order of liquid crystals was discussed.

Download Full-text

Stomatocyte structural color-barcode micromotors for multiplex assays

National Science Review ◽

10.1093/nsr/nwz185 ◽

2019 ◽

Vol 7 (3) ◽

pp. 644-651 ◽

Cited By ~ 5

Author(s):

Lijun Cai ◽

Huan Wang ◽

Yunru Yu ◽

Feika Bian ◽

Yu Wang ◽

...

Keyword(s):

Biomedical Applications ◽

Colloidal Crystal ◽

Structural Color ◽

Multiplex Detection ◽

Color Coding ◽

Functional Elements ◽

Structural Colors ◽

Multiplex Assays ◽

Magnetic Elements ◽

Extracting Solvent

Abstract Artificial micromotors have a demonstrated value in the biomedical area. Attempts to develop this technology tend to impart micromotors with novel functions to improve the values. Herein, we present novel structural color-barcode micromotors for the multiplex assays. We found that, by rapidly extracting solvent and assembling monodispersed nanoparticles in droplets, it could form stomatocyte colloidal crystal clusters, which not only showed striking structural colors and characteristic reflection peaks due to their ordered nanoparticles arrangement, but also provided effective cavities for the integration of functional elements. Thus, the micromotors with catalysts or magnetic elements in their cavities, as well as with the corresponding structural color coding, could be achieved by using the platinum and ferric oxide dispersed pre-gel to fill and duplicate the stomatocyte colloidal crystal clusters. We have demonstrated that the self-movement of these structural color-barcode micromotors could efficiently accelerate the mixing speed of the detection sample and greatly increase the probe–target interactions towards faster and more sensitive single or multiplex detection, and the magnetism of these barcode micromotors enables the flexible collection of the micromotors, which could facilitate the detection processes. These features make the stomatocyte structural color-barcode micromotors ideal for biomedical applications.

Download Full-text