المؤلفون: Reyes, G.¹ (AUTHOR) reyesvalgui@ciencias.unam.mx, Panayotaros, P.¹ (AUTHOR), Reyes, J. A.² (AUTHOR)

المصدر: Journal of Applied Physics. 1/14/2024, Vol. 135 Issue 2, p1-12. 12p.

مصطلحات موضوعية: *CHOLESTERIC liquid crystals, *ELECTROMAGNETIC waves, *SURFACE waves (Fluids), *ELECTROMAGNETIC wave propagation, *LIQUID crystals, *MAXWELL equations

مستخلص: We study an air–crown glass planar interface that includes a thin layer of a cholesteric liquid crystal doped with silver spheres of nanometer size. We propose a new theoretical model for the propagation of electromagnetic waves through the liquid crystal part and use the Marcuvitz–Schwinger form of the Maxwell equations to compute guided surface wave profiles. The results suggest the presence of anisotropic surface modes with negligible attenuation. The dependence of the surface wave parameters on the liquid crystal layer parameters can be used in liquid crystal-based sensors. [ABSTRACT FROM AUTHOR]

المؤلفون: Singh, Bhupendra Pratap¹ (AUTHOR), Hwang, Shug-June¹ (AUTHOR) june@nuu.edu.tw

المصدر: Analyst. 6/21/2024, Vol. 149 Issue 12, p3456-3467. 12p.

مصطلحات موضوعية: *POLYMER liquid crystals, *CHOLESTERIC liquid crystals, *POLYMER networks, *DETECTORS, *ETHANOL, *OPTICAL sensors

مستخلص: In this study, an optical sensor is developed, incorporating hydrogen-bonded photonic array dots containing poly(acrylic acid) (PAA) within a polymer cholesteric liquid crystal interpenetrating polymer network (PCLCIPN) framework, thereby effectively controlling porosity. This methodology involves the fabrication of a porous photonic film, subsequent infusion with a hydrogel (PAA), and precise UV-curing to generate patterned array dots. The sensor exhibits exceptional discriminatory capability between methanol and ethanol, accurately discerning their varying concentrations within alcohol solutions. The optical sensing performance of the film is rigorously evaluated through continuous monitoring of wavelength shifts in the transmission spectrum across various alcohol concentrations. Notably, the observed wavelength shifts demonstrate a linear correlation with the concentration of alcohol, thereby enabling precise quantitative analysis of the alcohol solutions. The sensor exhibits a sensitivity of 0.44 nm/% for ethanol concentrations ranging from 5% to 60%, increasing to 2.1 nm/% for concentrations between 60% and 80%. Similarly, for methanol, sensitivities of 0.68 nm/% (5–60%) and 2.2 nm/% (60–80%) are recorded. Remarkably, this sensitivity trend extends seamlessly to 1 : 1 ethanol/methanol ratios, with values of 0.49 nm/% (5–60%) and 2.25 nm/% (60–80%). Furthermore, these sensors demonstrate colorimetric response to different alcohols, rendering them accessible and cost-effective biosensors for visual detection, thus obviating the necessity for complex analytical instruments. [ABSTRACT FROM AUTHOR]

المؤلفون: Jirón, Vanessa^1,2 (AUTHOR), Rajabi, Mojtaba^1,3 (AUTHOR), Wang, Hao¹ (AUTHOR), Lavrentovich, Oleg D.^1,2,3 (AUTHOR) olavrent@kent.edu

المصدر: Communications Physics. 6/21/2024, Vol. 7 Issue 1, p1-9. 9p.

مصطلحات موضوعية: *LIQUID crystals, *CHOLESTERIC liquid crystals, *OPTICAL control, *BACILLUS subtilis, *ELECTRIC fields, *ACTIVE medium

مستخلص: Microscopic active droplets are of interest since they can be used to transport matter from one point to another. In this work, we demonstrate an approach to control the direction of active droplet propulsion by a photoresponsive cholesteric liquid crystal environment. The active droplet represents a water dispersion of bacterial Bacillus subtilis microswimmers. When placed in a cholesteric, a surfactant-stabilized active droplet distorts the local director field, producing a point defect-hedgehog, with fore-aft asymmetry, and allows for the chaotic motion of the bacteria inside the droplet to be rectified into directional motion. When the pitch of the cholesteric confined in a sandwich-like cell is altered by light irradiation, the droplet trajectory realigns along a new direction. The strategy allows for a non-contact dynamic control of active droplets trajectories and demonstrates the advantage of orientationally ordered media in control of active matter over their isotropic counterparts. The trajectory of the active droplets in an isotropic environment can be controlled by gradients of chemicals, physical obstacles, or by electric fields, but these methods are either static, transient, or require a complicated design. The authors demonstrate a simple optical method to control the trajectories of active droplets remotely by placing them in a photosensitive cholesteric liquid crystal environment. [ABSTRACT FROM AUTHOR]

المؤلفون: Li, Qihuan¹ (AUTHOR), Zou, Guo¹ (AUTHOR), Li, Dong¹ (AUTHOR), Liu, Chao¹ (AUTHOR), Gao, Wentong² (AUTHOR), Li, Yang¹ (AUTHOR) liyangchem@foxmail.com, Cheng, Yixiang¹ (AUTHOR) yxcheng@nju.edu.cn

المصدر: Advanced Optical Materials. 6/6/2024, Vol. 12 Issue 16, p1-8. 8p.

مصطلحات موضوعية: *CHOLESTERIC liquid crystals, *PHOSPHORESCENCE, *INTERMOLECULAR interactions, *LIQUID crystals

مستخلص: The high planarity and heavy‐atom effect of Pt(II) metallomesogens promote their stacking in the aggregated state and highly efficient phosphorescence. This makes them promising candidate materials for circularly polarized phosphorescence (CPP) triggered by using a chiral co‐assembly strategy. In this paper, a nematic phase, achiral robot‐like Pt(II) metallomesogen (TFPt) is synthesized, which combines two anchored chiral binaphthyl inducers (R/S1 or R/S2) to construct cholesteric liquid crystal (N*‐LC) co‐assemblies (R/S1)n‐(TFPt)1‐n and (R/S2)n‐(TFPt)1‐n via intermolecular interactions. The resultant N*‐LC chiral co‐assemblies (R1)0.03‐(TFPt)0.97 and (R2)0.03‐(TFPt)0.97 exhibit the strongest CPP emission with high dissymmetry factors (gem) of up to 0.18 and 0.27, respectively, stemming from the formation of regular helical nanofibers on spin‐coated films via co‐assembly process after thermal annealing at 165 °C. [ABSTRACT FROM AUTHOR]

المؤلفون: Reyes-Romero, Arturo¹ (AUTHOR) artrero77@gmail.com, Adrian Reyes, J.² (AUTHOR)

المصدر: Waves in Random & Complex Media. Jun2024, Vol. 34 Issue 3, p1702-1725. 24p.

مصطلحات موضوعية: *ELECTROMAGNETIC wave propagation, *CHOLESTERIC liquid crystals, *MAXWELL equations, *CONSTRUCTION slabs, *STOCHASTIC analysis, *PLANAR waveguides, *FILLER materials

مستخلص: A stochastic theoretical analysis of electromagnetic wave propagation inside a planar slab waveguide filled with a cholesteric material, whose azimuthal angular component on its director n is randomly fluctuating is presented in this article. By means of van Kampen systematic expansion method, Maxwell's electromagnetic equations with random dielectric tensor and appropriate boundary conditions are obtained. As numerical examples, the effects of the randomness on the propagating constant, on the ratio between magnetic and electric modes, on the field profiles, and on the energy flow are presented and discussed. The results in this paper are consistent with those corresponding to the deterministic conventional waveguide. [ABSTRACT FROM AUTHOR]

المؤلفون: Tseng, Hsin-Kai¹ (AUTHOR), Wu, Po-Chang¹ (AUTHOR), Lee, Wei¹ (AUTHOR) tonywijaya0199@yahoo.com.tw

المصدر: Molecules. Jun2024, Vol. 29 Issue 11, p2607. 12p.

مصطلحات موضوعية: *OPTICAL switching, *CHOLESTERIC liquid crystals, *SUBSTRATES (Materials science), *COLOR

مستخلص: We propose a double-cell cholesteric liquid crystal (CLC) device composed of a left-handed (LH) CLC cell with a pair of sheet electrodes and a right-handed (RH) CLC cell with a tri-electrode configuration characterized by a sheet electrode on the top and an interdigitated electrode on the bottom substrates. Bi-reflected color tuning and hyper-reflective color switching are revealed from this cell stack via the electrothermal control of the central wavelengths of the LH- and RH-bandgaps by voltage-induced pseudo-dielectric heating. The two CLCs are thermally sensitive and exhibit overlapped bandgaps in the field-off state with nearly identical temperature dependence, resulting in a hyper-reflective color at 720 nm at 23.4 °C and 380 nm at 29.8 °C. Upon the application of 4 Vrms at 2 MHz across the stacked device to induce pseudo-dielectric heating, two reflective colors can be resolved due to asymmetrical temperature elevations. Accordingly, the difference in wavelength between the two colors increases with increasing voltage through a series cell connection, while maintaining approximately constant via a parallel connection. This study provides a feasible pathway to developing a multifunctional device with electrothermally tunable bi-reflected and hyper-reflective states based on two conventional cell geometries, which is promising for lasers and color-related display applications. [ABSTRACT FROM AUTHOR]

المؤلفون: Qu, Guangyin¹ (AUTHOR), Hu, Lei^1,2 (AUTHOR), Li, Siqi¹ (AUTHOR), Kuai, Yan¹ (AUTHOR), Cao, Zhigang¹ (AUTHOR), Liu, Yu¹ (AUTHOR), Xie, Kang³ (AUTHOR), Yu, Benli¹ (AUTHOR), Hu, Zhijia¹ (AUTHOR) zhijiahu@ahu.edu.cn

المصدر: Laser & Photonics Reviews. Jun2024, Vol. 18 Issue 6, p1-9. 9p.

مصطلحات موضوعية: *SOLID-state lasers, *CHOLESTERIC liquid crystals, *LIQUID crystals, *FLUORESCENCE yield, *DYE lasers, *PHOTONS

مستخلص: Liquid‐crystal random lasers (LCRLs) represent a burgeoning field in soft‐matter photonics, holding promise for ushering in an era of ultrathin, versatile laser sources. Such lasers encompass a multitude of remarkable features, including wide‐band tunability, large coherence area and, in some cases, multidirectional emission. In this paper, an LCRL is developed by doping a laser dye, pyrromethene 597 (PM597), into cholesteric LC, but achieving a wide‐range wavelength‐controllable (560–720 nm) bandgap lasing through voltage control. Bandgap lasing intriguingly occurs in media with extremely low dye gain, which is mainly contributed by the extremely high photon density of states (DOS) at the edge of the LC bandgap. In addition, the utilization rate of the fluorescence spectrum (550–750 nm) of laser dye PM597 is as high as 80%. The multivariate linear regression model is used to characterize the inherent relationship between the lasing intensity emitted by LC and the photon DOS, fluorescence quantum yield, and internal scattering under specific pumping energy. This model shows the potential to predict the critical conditions of laser emission accurately and provides the capability to design and fabricate large‐scale multifunctional responsive photonic crystals using a simple fabrication procedure. [ABSTRACT FROM AUTHOR]

المؤلفون: Zhang, Xuan¹ (AUTHOR), Li, Lin² (AUTHOR), Chen, Yuanhao¹ (AUTHOR), Valenzuela, Cristian¹ (AUTHOR), Liu, Yuan¹ (AUTHOR), Yang, Yanzhao¹ (AUTHOR), Feng, Yufan¹ (AUTHOR), Wang, Ling^1,3 (AUTHOR) lwang17@tju.edu.cn, Feng, Wei^1,3 (AUTHOR) weifeng@tju.edu.cn

المصدر: Angewandte Chemie. 5/27/2024, Vol. 136 Issue 22, p1-11. 11p.

مصطلحات موضوعية: *CHOLESTERIC liquid crystals, *QUANTUM dots, *PEROVSKITE, *LUMINESCENCE, *STRUCTURAL colors, *FLEXIBLE display systems

مستخلص: Endowing perovskite quantum dots (PQDs) with circularly polarized luminescence (CPL) offers great promise for innovative chiroptical applications, but the existing strategies are inefficient in acquiring stimuli‐responsive flexible chiral perovskite films with large, tunable dissymmetry factor (glum) and long‐term stability. Here, we report a strategy for the design and synthesis of luminescent cholesteric liquid crystal elastomer (Lumin‐CLCE) films with mechanically tunable CPL, which is enabled by liquid crystal‐templated chiral self‐assembly and in situ covalent cross‐linking of judiciously designed photopolymerizable CsPbX3 (X=Cl, Br, I) PQD nanomonomers into the elastic polymer networks. The resulting Lumin‐CLCE films showcase circularly polarized structural color in natural light and noticeable CPL with a maximum glum value of up to 1.5 under UV light. The manipulation of CPL intensity and rotation direction is achieved by controlling the self‐assembled helicoidal nanostructure and the handedness of soft helices. A significant breakthrough lies in the achievement of a reversible, mechanically tunable perovskite‐based CPL switch activated by biaxial stretching, which enables flexible, dynamic anti‐counterfeiting labels capable of decrypting preset information in specific polarization states. This work can provide new insights for the development of advanced chiral perovskite materials and their emerging applications in information encryption, flexible 3D displays, and beyond. [ABSTRACT FROM AUTHOR]

المؤلفون: Zhou, Ziyuan¹ (AUTHOR) zzhou16@kent.edu, Zhang, Xinfang¹ (AUTHOR), Halder, Suman² (AUTHOR) shalder1@kent.edu, Hu, Lang¹ (AUTHOR) lhu4@kent.edu, Shin, Yunho¹ (AUTHOR) yshin2@kent.edu, Yang, Deng‐Ke^1,2 (AUTHOR) dyang@kent.edu

المصدر: Advanced Optical Materials. May2024, Vol. 12 Issue 14, p1-13. 13p.

مصطلحات موضوعية: *CHOLESTERIC liquid crystals, *ELECTROCHROMIC windows, *LIQUID crystals

مستخلص: Windows are used everywhere, from buildings to vehicles. Smart switchable windows are highly sought‐after in order to reduce energy consumption. An ideal smart window should have two functions. First, it should be able to control privacy. Second, it should be able to control radiant energy flow. Here, a smart window is reported that possesses the two functions. The smart window is based on a dichroic dye‐doped cholesteric liquid crystal. It exhibits two stable states in the absence of applied voltage. One of them is the planar state that is optically absorbing without haze and can control radiant energy flow. The other state is the focal conic state that is optically scattering and can control privacy. Furthermore, when voltage is applied, the liquid crystal is switched to a heliconical state, where the transmittance can be tuned continuously. Thanks to its superior performance, this smart window has a big potential for applications in architectural and vehicle windows. [ABSTRACT FROM AUTHOR]

المؤلفون: Seylan Akış, Melike¹ (AUTHOR), Kemiklioglu, Emine¹ (AUTHOR) ekemikli@kent.edu, Kemiklioğlu, Uğur² (AUTHOR)

المصدر: International Journal of Polymeric Materials & Polymeric Biomaterials. 2024, Vol. 73 Issue 7, p556-563. 8p.

مصطلحات موضوعية: *COMPOSITE membranes (Chemistry), *CHOLESTERIC liquid crystals, *POLYMER liquid crystals, *CONTACT angle, *BLOOD proteins, *BLOOD coagulation, *BIOLOGICAL membranes

مستخلص: In this study cinnamaldehyde (CA) doped polyurethane cholesteryl pelargonate cholesteric liquid crystal composite membranes were produced and their properties were examined for use in biological applications. The relationship between the blood coagulation and protein adsorption was studied and the results showed that increasing CA concentration allowed an improvement in biological properties of them. Additionally, the effect of CA on the hyrophobicity of these membranes was investigated by determining water holding capacity, contact angles. The mechanical strength of these membranes were determined and it was found that their strength increased and the ability to elongate decreased with an increasing CA dopant concentration. [ABSTRACT FROM AUTHOR]