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Recent advances in the manipulation of circularly polarised light with cellulose nanocrystal films
摘要： Significant advances have been made to control the iridescence and the selective reflection of left circularly polarised (LCP) light, and transmission of right circularly polarised (RCP) light of solid films prepared from cellulose nanocrystals (CNCs). However the manipulation of the photonic properties of the CNCs films, which reflect both RCP and LCP light is less investigated. Solid films prepare from natural sources as CNCs have advantageous characteristics that are absent in other synthetic structures, such as wide availability and renewability. Here we review and compare recent research activity involving the production and characterization of photonic band gap structures resulting from an anisotropic layer inserted between two cholesteric layers with different helical pitches but the same handedness. We make connections between systems existing in Nature and synthetic ones with the hope of advancing in the production and manipulation of CNCs-based photonic structures.
关键词： Cellulose nanocrystals,Photonics,Circularly polarised light,Bio-inspired materials,Iridescence,Liquid crystals
更新于2025-09-10 09:29:36
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Scattering-/absorption-mode light shutters based on dye-doped fingerprint chiral textures
摘要： Scattering-/absorption-mode light shutters based on dye-doped fingerprint chiral textures (DdFCTs) are demonstrated. DdFCTs in a liquid crystal (LC) cell treated with homeotropic alignment are initially stable FCTs due to the vertical surface anchoring force (SAF). The LCs completely rotate to homeotropic orientation from stable FCTs by applying a suitable operation voltage (Vop). Furthermore, when the Vop is switched off, the LCs transform into temporary focal conic textures with lifetimes of few seconds from the homeotropic orientation, the LCs then transform into unstable FCTs. Finally, the unstable FCTs spontaneously return to the initial stable FCTs. The light absorption of DdFCTs in the stable FCTs/unstable FCTs/field-induced multi-domain FCTs is independent of the polarization of the incident light. The operation mechanism of the proposed DdFCTs is also discussed. Most importantly, the response time and the required Vop to rotate all LCs to homeotropic orientation in DdFCTs from stable FCTs in LC cells treated with homeotropic alignment layers are respectively shorter and lower than those in common dye-doped cholesteric LCs (DdCLCs) from stable planar textures in LC cells treated with homogeneous alignment layers. Comparing with DdCLCs, about 20% Vop can be reduced in DdFCTs. The cause can be understood since the Vop applied onto the DdFCTs is fully dedicated to unwind the helical structures.
关键词： Cholesterics,Liquid crystals,Scattering,Dichroic dyes,Light shutter,Absorption
更新于2025-09-10 09:29:36
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Synchronous enhancement and stabilization of graphene oxide liquid crystals: Inductive effect of sodium alginates in different concentration zones
摘要： A facile way to simultaneously induce the formation and enhance the stability of graphene oxide liquid crystals (GO LCs) is reported. Sodium alginate (SA) with both inductive effect and stabilization effect was added into GO suspensions to prepare LCs at low concentration that could survive harsh conditions. Most importantly, different concentration zones of SA brought significantly different LCs degree and stability, which possessed distinct charge properties, rheological behaviors and chain morphology. Adding 0.5 % SA located in entangled semi-dilute regime could induce the isotropic-nematic transition of GO at low concentration (< 0.035 %) and showed excellent liquid crystalline behavior due to the enhanced electrostatic repulsion of GO/SA colloids, while 1% SA located in concentrated solution regime brought better tolerance to NaCl, MgCl2, FeCl3, serum and pH of 1-13 due to the stronger bounding effect of entanglement network structure to countra-ions. This work develops a simple and eco-friendly method to prepare stable GO LCs at low GO concentration with application potentials especially in biomedical field, and the relationship between the concentration zones of SA and LCs behavior offers theoretical guidance for the self-assembly of GO macrostructures and design and efficient processing of its composites.
关键词： Sodium alginate,Liquid crystals,Graphene oxide
更新于2025-09-10 09:29:36
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Liquid Crystals: A Novel Approach for Cancer Detection and Treatment
摘要： Liquid crystals are defined as the fourth state of matter forming between solid and liquid states. Earlier the applications of liquid crystals were confined to electronic instruments, but recent research findings suggest multiple applications of liquid crystals in biology and medicine. Here, the purpose of this review article is to discuss the potential biological impacts of liquid crystals in the diagnosis and prognosis of cancer along with the risk assessment. In this review, we also discussed the recent advances of liquid crystals in cancer biomarker detection and treatment in multiple cell line models. Cases reviewed here will demonstrate that cancer diagnostics based on the multidisciplinary technology and intriguingly utilization of liquid crystals may become an alternative to regular cancer detection methodologies. Additionally, we discussed the formidable challenges and problems in applying liquid crystal technologies. Solving these problems will require great effort and the way forward is through the multidisciplinary collaboration of physicists, biologists, chemists, material-scientists, clinicians, and engineers. The triumphant outcome of these liquid crystals and their applications in cancer research would be convenient testing for the detection of cancer and may result in treating the cancer patients non-invasively.
关键词： biosensor,biomarker,antitumor drug,liquid crystals,cancers
更新于2025-09-10 09:29:36
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The effect of the length of terminal n-alkyl carboxylate chain on self-assembling and photosensitive properties of chiral lactic acid derivatives
摘要： A new series of photosensitive azo materials possessing a chiral alkyl lactate moiety and terminal n-alkyl carboxylate unit close to the azo group has been synthesised and studied. The length of the n-alkyl carboxylate chain has been systematically varied in order to establish the effect of the molecular structure on the self-assembling behaviour. Two series of materials possessing hexyl and dodecyl alkyl chains in the chiral part of the molecule have been studied. It has been shown that the length of both the alkyl chains strongly influences the mesomorphic behaviour, however, each chiral/achiral chain has different utility to tune the mesomorphic properties. With exception of the compound with the longest chains, all studied compounds exhibited the chiral tilted ferroelectric smectic C* phase. Based on the combination of terminal alkyl chains, chiral nematic, orthogonal smectic A*, and twist grain boundary smectic A* phases have been detected on cooling beyond the SmC* phase. The presence of the photosensitive functional N=N group in the molecular core allowed further tuning of the material properties by UV light illumination. The E-to-Z photoisomerization of the azo group and subsequent thermal back-isomerisation have been studied in solution by nuclear magnetic resonance and most importantly in the mesophases on bulk samples. We report on UV-induced isothermal switching from chiral smectic and nematic mesophases directly into the isotropic phase, respectively, and differences in the textures of mesophase upon restoration of the ordered liquid.
关键词： E-Z isomerisation,ferroelectric phase,photosensitive liquid crystals,azo group,chiral liquid crystals,NMR spectroscopy,optical switches
更新于2025-09-09 09:28:46
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Disappearance of Reflection Color by Photopolymerization of Lyotropic Cholesteric Liquid Crystals from Cellulose Derivatives
摘要： In this communication, we report on the disappearance of reflection color by photopolymerization of an acrylate monomer in lyotropic cholesteric liquid crystals from a cellulose derivative for color image applications. When a hydroxypropyl cellulose (HPC) derivative possessing propionyl side chains (HPC-Pr) was homogeneously dissolved in a liquid monomer of 4-hydroxybutyl acrylate (4HBA), we obtained lyotropic cholesteric liquid crystals (HPC-Pr_4HBA) with a Bragg reflection peak in the visible wavelength range. Such reflection wavelength was controllable by not only temperature, but also concentration of HPC-Pr in 4HBA. We found that Bragg reflection peak of lyotropic HPC-Pr_4HBA mixture disappears by photopolymerization of 4HBA, thereby leading to the fabrication of a photolithographic color image. This report provides promising clues to fabricate intriguing photonic devices adopted with cellulose derivatives by utilizing such Bragg reflection characteristics.
关键词： Color image,Cholesteric liquid crystals,Lyotropic liquid crystals,Cellulose,Bragg reflection,Photopolymerization
更新于2025-09-09 09:28:46
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Ultra-fast adaptive optical micro-lens arrays based on stressed liquid crystals
摘要： We characterized the optical properties of a photoresist-based micro-lens using a stressed liquid crystal matrix for high-speed variation of the focal distance. We also determined the operational parameters for the adaptive optical spherical and cylindrical micro-lens arrays. The resulting optical elements feature fast response times, around 1 ms, with a focal length range of 2600-970 μm.
关键词： stressed liquid crystals,adaptive optical micro-lens arrays,focal length variation,fast response times
更新于2025-09-09 09:28:46
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Photoactive Functional Soft Materials (Preparation, Properties, and Applications) || Photochemical Chirality Induction and Inversion in Soft Materials
摘要： Chirality or “handedness” is a prerequisite of the biological world, where life exists in a specific chirality. In living organisms, almost all the sugars are exclusively right‐handed (d‐isomer), amino acids are left‐handed (l‐isomer), and DNA coils assemble into right‐handed helices. The reason behind this homochirality is still an unresolved issue. Inspired by the natural homochirality, the scientific community has been interested in exploring the mechanism of transmission of chirality from the molecular level of monomeric units to the macro‐ or supramolecular level, as well as the origin of chirality. The supramolecular chirality in nature from self‐assembled achiral molecules and its specific handedness play a crucial role in the evolution of life and the development of supramolecular materials. While the chirality of molecules is of configurational and conformational origin, supramolecular level chirality arises from the organization of molecules, with formation of a chiral superstructure by means of long‐range positional and orientational orders of molecules.
关键词： Supramolecular,Polymers,Circularly Polarized Light,Photochromic Switches,Helical Structures,Liquid Crystals,Photochemical,Self-Assembly,Soft Materials,Chirality
更新于2025-09-09 09:28:46
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Infiltrated Photonic Crystal Fibers for Sensing Applications
摘要： Photonic crystal ?bers (PCFs) are a special class of optical ?bers with a periodic arrangement of microstructured holes located in the ?ber’s cladding. Light con?nement is achieved by means of either index-guiding, or the photonic bandgap effect in a low-index core. Ever since PCFs were ?rst demonstrated in 1995, their special characteristics, such as potentially high birefringence, very small or high nonlinearity, low propagation losses, and controllable dispersion parameters, have rendered them unique for many applications, such as sensors, high-power pulse transmission, and biomedical studies. When the holes of PCFs are ?lled with solids, liquids or gases, unprecedented opportunities for applications emerge. These include, but are not limited in, supercontinuum generation, propulsion of atoms through a hollow ?ber core, ?ber-loaded Bose–Einstein condensates, as well as enhanced sensing and measurement devices. For this reason, in?ltrated PCF have been the focus of intensive research in recent years. In this review, the fundamentals and fabrication of PCF in?ltrated with different materials are discussed. In addition, potential applications of in?ltrated PCF sensors are reviewed, identifying the challenges and limitations to scale up and commercialize this novel technology.
关键词： optical fiber sensors,photonic crystal fibers,optofluidics,plasmonic sensors,liquid crystals
更新于2025-09-09 09:28:46
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Reference Module in Materials Science and Materials Engineering || Liquid Crystals Under High Pressure
摘要： From a historical perspective, the first high pressure experiments were carried out soon after the discovery of liquid crystals, although the field became more active much later. Despite being considered as equivalent thermodynamic variables, temperature (T) and pressure (P) act differently on liquid crystals (LC), with the former affecting the rotational and vibration energy dependent parameters, and the latter altering the intermolecular distances. This feature, in combination with the fact that relatively low pressures bring about significant changes in the properties of LCs, has provided impetus for the studies described here. These investigations have not only augmented the knowledge on LCs obtained at atmospheric pressure, but have provided valuable insights into the understanding of complex fluids (Chandrasekhar and Shashidhar, 1979; Pollmann, 1999; Urban, 2014); the studies have been carried out using apparatus such as optical transmission, DTA, calorimetry, dielectric, NMR, XRD, volumetry, and Raman, detailed in these articles. For the description of the structures of the LC mesophases, numbering more than 40, the reader may refer to the article.
关键词： ferroelectric properties,mesomorphism,liquid crystals,nematic-isotropic transition,high pressure
更新于2025-09-09 09:28:46