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https://www.readbyqxmd.com/read/28821101/cholesteric-film-of-cu-ii-doped-cellulose-nanocrystals-for-colorimetric-sensing-of-ammonia-gas
#1
Shidong Dai, Nana Prempeh, Dagang Liu, Yimin Fan, Mingyue Gu, Yu Chang
With the increasing demand of environmental monitoring for toxic and odorous ammonia gas it is desired to develop specific green, cost-effective and in situ passive colorimetric alternatives to current complex instrumentations. In this work, we designed an ammonia gas sensor based on cholesteric liquid crystal films of copper(II)-doped cellulose nanocrystals (CNCCu(II)) whose structure, optical and sensing properties were investigated. The hybrid films using the low doping Cu(II) as a color-tuning agent inherited the chiral nematic signature and optical activity of CNCs, suggesting a strong chelation between copper ions and negatively charged CNCs...
October 15, 2017: Carbohydrate Polymers
https://www.readbyqxmd.com/read/28819662/chiral-amplification-of-disodium-cromoglycate-chromonics-induced-by-a-codeine-derivative
#2
F Berride, E Troche-Pesqueira, G Feio, E J Cabrita, T Sierra, A Navarro-Vázquez, M M Cid
Chromonic liquid crystals (CLC) are lyotropic phases formed by discotic mesogens in water. Simple chiral dopants such as amino acids have been reported to turn chromonic liquid crystals into their cholesteric counterparts. Here we report a chirality amplification effect in the nematic phase of a 9 wt% disodium cromoglycate (DSCG) lyotropic liquid crystal (LLC) upon doping with a water-soluble codeine derivative. The transition on cooling the isotropic to the nematic phase showed the presence of homochiral spindle-shaped droplets (tactoids)...
August 18, 2017: Soft Matter
https://www.readbyqxmd.com/read/28815232/blue-shifting-tuning-of-the-selective-reflection-of-polymer-stabilized-cholesteric-liquid-crystals
#3
Kyung Min Lee, Vincent P Tondiglia, Nicholas P Godman, Claire M Middleton, Timothy J White
We report on electrically-induced, large magnitude (>300 nm), and reversible tuning of the selective reflection in polymer stabilized cholesteric liquid crystals (PSCLCs) prepared from negative dielectric anisotropy nematic liquid crystal hosts. The electrically-induced blue shift in the selective reflection of the PSCLCs is distinguished from our prior reports of bandwidth broadening and red-shifting tuning of the selective reflection in PSCLCs. The dominant factor in delineating the electro-optic response of the PSCLCs detailed here are the preparation conditions...
August 17, 2017: Soft Matter
https://www.readbyqxmd.com/read/28810771/switching-dynamics-in-cholesteric-liquid-crystal-emulsions
#4
F Fadda, G Gonnella, D Marenduzzo, E Orlandini, A Tiribocchi
In this work we numerically study the switching dynamics of a 2D cholesteric emulsion droplet immersed in an isotropic fluid under an electric field, which is either uniform or rotating with constant speed. The overall dynamics depend strongly on the magnitude and on the direction (with respect to the cholesteric axis) of the applied field, on the anchoring of the director at the droplet surface and on the elasticity. If the surface anchoring is homeotropic and a uniform field is parallel to the cholesteric axis, the director undergoes deep elastic deformations and the droplet typically gets stuck into metastable states which are rich in topological defects...
August 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28747672/fast-switching-cholesteric-liquid-crystal-optical-beam-deflector-with-polarization-independence
#5
Xiaobing Shang, Laurens Meeus, Dieter Cuypers, Herbert De Smet
Optical beam deflectors based on the combination of cholesteric liquid crystals and polymer micro gratings are reported. Dual frequency cholesteric liquid crystal (DFCh-LC) is adopted to accelerate the switching from the homeotropic state back to the planar state. Polarization independent beam steering components are realized whose transmission versus the polarizing angle only varies 4.4% and 2.6% for the planar state and the homeotropic state, respectively. A response time of 451 ms is achieved for DFCh-LC-grating beam deflectors, which is fast compared to other nematic LC beam steerers with similar LC thickness...
July 26, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28662741/cellulose-nanocrystals-surface-modification-applications-and-opportunities-at-interfaces
#6
Jens C Natterodt, Alke Petri-Fink, Christoph Weder, Justin O Zoppe
Cellulose nanocrystals (CNCs) are rod-like nano-scale particles that are widely available in nature and have recently gained great interest in both research and industry, due to their high strength, high crystallinity, high surface area, low density, biodegradability and low toxicity. CNCs can be easily extracted from natural cellulose sources and are broadly useful, for example in polymer reinforcement, paper manufacturing, and rheology modification. The high density of functional groups on the surface of CNCs allows various chemical surface modifications, which permit tuning the properties of CNCs over a wide range...
June 28, 2017: Chimia
https://www.readbyqxmd.com/read/28657731/structural-effects-of-single-mutations-in-a-filamentous-viral-capsid-across-multiple-length-scales
#7
Gili Abramov, Rona Shaharabani, Omry Morag, Ram Avinery, Anat Haimovich, Inbal Oz, Roy Beck, Amir Goldbourt
Filamentous bacteriophage (phage) are single-stranded DNA viruses that infect bacteria. Single-site mutants of fd phage have been studied by magic-angle spinning nuclear magnetic resonance and by small-angle X-ray scattering. Detailed analysis has been performed that provides insight into structural variations on three length scales. The results, analyzed in conjunction with existing literature data, suggest that a single charge mutation on the capsid surface affects direct interviral interactions but not the structure of individual particles or the macroscale organization...
July 17, 2017: Biomacromolecules
https://www.readbyqxmd.com/read/28635143/controlling-the-photonic-properties-of-cholesteric-cellulose-nanocrystal-films-with-magnets
#8
Bruno Frka-Petesic, Giulia Guidetti, Gen Kamita, Silvia Vignolini
The self-assembly of cellulose nanocrystals is a powerful method for the fabrication of biosourced photonic films with a chiral optical response. While various techniques have been exploited to tune the optical properties of such systems, the presence of external fields has yet to be reported to significantly modify their optical properties. In this work, by using small commercial magnets (≈ 0.5-1.2 T) the orientation of the cholesteric domains is enabled to tune in suspension as they assemble into films...
June 21, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28630681/imaging-optical-scattering-of-butterfly-wing-scales-with-a-microscope
#9
Jinxin Fu, Beom-Jin Yoon, Jung Ok Park, Mohan Srinivasarao
A new optical method is proposed to investigate the reflectance of structurally coloured objects, such as Morpho butterfly wing scales and cholesteric liquid crystals. Using a reflected-light microscope and a digital single-lens reflex (DSLR) camera, we have successfully measured the two-dimensional reflection pattern of individual wing scales of Morpho butterflies. We demonstrate that this method enables us to measure the bidirectional reflectance distribution function (BRDF). The scattering image observed in the back focal plane of the objective is projected onto the camera sensor by inserting a Bertrand lens in the optical path of the microscope...
August 6, 2017: Interface Focus
https://www.readbyqxmd.com/read/28630672/circularly-polarized-reflection-from-the-scarab-beetle-chalcothea-smaragdina-light-scattering-by-a-dual-photonic-structure
#10
Luke T McDonald, Ewan D Finlayson, Bodo D Wilts, Pete Vukusic
Helicoidal architectures comprising various polysaccharides, such as chitin and cellulose, have been reported in biological systems. In some cases, these architectures exhibit stunning optical properties analogous to ordered cholesteric liquid crystal phases. In this work, we characterize the circularly polarized reflectance and optical scattering from the cuticle of the beetle Chalcothea smaragdina (Coleoptera: Scarabaeidae: Cetoniinae) using optical experiments, simulations and structural analysis. The selective reflection of left-handed circularly polarized light is attributed to a Bouligand-type helicoidal morphology within the beetle's exocuticle...
August 6, 2017: Interface Focus
https://www.readbyqxmd.com/read/28618483/heterogeneous-colloidal-particles-immersed-in-a-liquid-crystal
#11
Setarehalsadat Changizrezaei, Colin Denniston
In this paper, we explore anisotropic interactions between particles with heterogeneous boundary conditions inside both nematic and cholesteric liquid crystals. The results show that when particles are put at different distances and angles with respect to each other, new types of defect structures are produced, depending on the relative distances and directions. In a cholesteric liquid crystal, the value of the pitch affects the defect structures and induced forces. Moreover, it was observed that it is energetically favorable for the particles to remain in a plane parallel to the far-field director in a nematic liquid crystal, while for particles immersed in a cholesteric there are multiple energy minima not all located in the same plane...
May 2017: Physical Review. E
https://www.readbyqxmd.com/read/28590069/controllable-dynamic-zigzag-pattern-formation-in-a-soft-helical-superstructure
#12
Zhi-Gang Zheng, Rafael S Zola, Hari Krishna Bisoyi, Ling Wang, Yannian Li, Timothy J Bunning, Quan Li
Zigzag pattern formation is a common and important phenomenon in nature serving a multitude of purposes. For example, the zigzag-shaped edge of green leaves boosts the transportation and absorption of nutrients. However, the elucidation of this complicated shape formation is challenging in fluid mechanics and soft condensed matter systems. Herein, a dynamically reconfigurable zigzag pattern deformation of a soft helical superstructure is demonstrated in a photoresponsive self-organized cholesteric liquid crystal superstructure under the simultaneous influence of an applied electric field and light irradiation...
August 2017: Advanced Materials
https://www.readbyqxmd.com/read/28589190/cholesteric-liquid-crystals-in-living-matter
#13
REVIEW
Michel Mitov
Liquid crystals play an important role in biology because the combination of order and mobility is a basic requirement for self-organisation and structure formation in living systems. Cholesteric liquid crystals are omnipresent in living matter under both in vivo and in vitro conditions and address the major types of molecules essential to life. In the animal and plant kingdoms, the cholesteric structure is a recurring design, suggesting a convergent evolution to an optimised left-handed helix. Herein, we review the recent advances in the cholesteric organisation of DNA, chromatin, chitin, cellulose, collagen, viruses, silk and cholesterol ester deposition in atherosclerosis...
June 14, 2017: Soft Matter
https://www.readbyqxmd.com/read/28571371/publisher-s-note-perturbative-density-functional-methods-for-cholesteric-liquid-crystals-j-chem-phys-146-184504-2017
#14
Maxime M C Tortora, Jonathan P K Doye
No abstract text is available yet for this article.
May 28, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28530665/molecular-engineering-of-chiral-colloidal-liquid-crystals-using-dna-origami
#15
Mahsa Siavashpouri, Christian H Wachauf, Mark J Zakhary, Florian Praetorius, Hendrik Dietz, Zvonimir Dogic
Establishing precise control over the shape and the interactions of the microscopic building blocks is essential for design of macroscopic soft materials with novel structural, optical and mechanical properties. Here, we demonstrate robust assembly of DNA origami filaments into cholesteric liquid crystals, one-dimensional supramolecular twisted ribbons and two-dimensional colloidal membranes. The exquisite control afforded by the DNA origami technology establishes a quantitative relationship between the microscopic filament structure and the macroscopic cholesteric pitch...
August 2017: Nature Materials
https://www.readbyqxmd.com/read/28497826/twisting-with-a-twist-supramolecular-helix-fluctuations-in-chiral-nematics
#16
Henricus Herman Wensink, Claudia Ferreiro-Córdova
Most theoretical descriptions of lyotropic cholesteric liquid crystals to date focus on homogeneous systems in which the rod concentration, as opposed to the rod orientation, is uniform. In this work, we build upon the Onsager-Straley theory for twisted nematics and study the effect of weak concentration gradients, generated by some external potential, on the cholesteric twist. We apply our theory to chiral nematics of nanohelices in which the supramolecular helix sense is known to spontaneously change sign upon variation of particle concentration, passing through a so-called compensation point at which the mesoscopic twist vanishes...
May 31, 2017: Soft Matter
https://www.readbyqxmd.com/read/28489951/direct-observation-of-changes-in-focal-conic-domains-of-cholesteric-films-induced-by-ultraviolet-irradiation
#17
Olga V Sinitsyna, Alexey Yu Bobrovsky, Georgy B Meshkov, Igor V Yaminsky, Valery P Shibaev
The helical supramolecular structure of cholesteric liquid crystalline (LC) films predetermines their outstanding optical properties and the unique nanostructure of their surface. The introduction of photochromic dopants in these films opens up an interesting possibility for creation of smart cholesteric materials with photocontrollable optical and photovariable surface properties. Using atomic force microscopy (AFM), we performed in situ measurements of the surface topography of cyclosiloxane LC cholesteric oligomer films during the cholesteric helix twisting caused by their preliminary ultraviolet (UV) irradiation...
May 23, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28429181/hydrodynamic-instabilities-in-active-cholesteric-liquid-crystals
#18
Carl A Whitfield, Tapan Chandra Adhyapak, Adriano Tiribocchi, Gareth P Alexander, Davide Marenduzzo, Sriram Ramaswamy
We describe the basic properties and consequences of introducing active stresses, with principal direction along the local director, in cholesteric liquid crystals. The helical ground state is found to be linearly unstable to extensile stresses, without threshold in the limit of infinite system size, whereas contractile stresses are hydrodynamically screened by the cholesteric elasticity to give a finite threshold. This is confirmed numerically and the non-linear consequences of instability, in both extensile and contractile cases, are studied...
April 2017: European Physical Journal. E, Soft Matter
https://www.readbyqxmd.com/read/28421224/chirality-induced-helical-self-propulsion-of-cholesteric-liquid-crystal-droplets
#19
Takaki Yamamoto, Masaki Sano
We report the first experimental realization of a chiral artificial microswimmer exhibiting helical motion without any external fields. We discovered that a cholesteric liquid crystal (CLC) droplet with a helical director field swims in a helical path driven by the Marangoni flow in an aqueous surfactant solution. We also showed that the handedness of the helical path is reversed when that of the CLC droplet is reversed by replacing the chiral dopant with the enantiomer. In contrast, nematic liquid crystal (NLC) droplets exhibited ballistic motions...
May 14, 2017: Soft Matter
https://www.readbyqxmd.com/read/28415267/dispersion-relation-for-electromagnetic-propagation-in-stochastic-dielectric-and-magnetic-helical-photonic-crystals
#20
Carlos G Avendaño, Arturo Reyes
We theoretically study the dispersion relation for axially propagating electromagnetic waves throughout a one-dimensional helical structure whose pitch and dielectric and magnetic properties are spatial random functions with specific statistical characteristics. In the system of coordinates rotating with the helix, by using a matrix formalism, we write the set of differential equations that governs the expected value of the electromagnetic field amplitudes and we obtain the corresponding dispersion relation...
March 2017: Physical Review. E
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