Light and Humidity Dual-Responsive Anti-Counterfeiting Films Based on Hydrogen-Bonded Cholesteric Liquid Crystal Polymers with Spiropyran.

There is still significant room for improvement when combining structural color with fluorescence patterns in dual anti-counterfeiting and dynamic anti-counterfeiting labels. In this study, we achieved significant breakthroughs under dual anti-counterfeiting conditions by using the structural color properties of the hydrogen-bonded cholesteric liquid crystal (HBCLC) and combining them with the fluorescence dye spiropyran (SP) to create anti-counterfeiting patterns. The anti-counterfeiting label can only display storage information after meeting the conditions of humidity and ultraviolet light (UV) and has the functions of dynamic encryption and repeated reading. We adjusted the center of the reflection band of the HBCLC film to transition from red to infrared under 40-90% relative humidity (RH) conditions and used it as a background film to draw anti-counterfeiting patterns with SP. Since these fluorescence dyes can switch between merocyanine (MC) (red) and SP (colorless) under UV and visible light conditions, when combined with the HBCLC, orthogonal dynamic encryption was achieved. Additionally, with the adsorption of SP, the reflection band of HBCLC films under the same humidity range increased from around 160 nm to around 260 nm, greatly improving the sensitivity to humidity changes. Furthermore, under UV conditions, it can still emit red fluorescence, demonstrating a polymorphic encryption feature, which greatly increased the complexity of the anti-counterfeiting pattern with significant significance to dynamic anti-counterfeiting and information storage.

Correction: A liquid-crystal-based immunosensor for the detection of cardiac troponin I.

Correction for 'A liquid-crystal-based immunosensor for the detection of cardiac troponin I' by Chunli Xia et al., Analyst, 2020, 145, 4569-4575, DOI: 10.1039/D0AN00425A.

A liquid-crystal-based immunosensor for the detection of cardiac troponin I.

Cardiac troponin I (cTnI) is one of the most sensitive and specific markers of myocardial cell injury, which can detect even minor myocardial damages. It is recognized as the main biochemical marker of the rapid diagnosis of acute myocardial infarction (AMI) and acute coronary syndrome (ACS). In this study, a label-free biosensor that utilizes the birefringence property of a nematic liquid crystal (LC) for the detection of cTnI is demonstrated. A chemically sensitive film with specific molecular recognition ability was decorated on the surface of a substrate, and the LC molecules were arranged in a vertically oriented order under the influence of the sensitive film, and a dark background signal was obtained using a polarizing optical microscope. When the antigen-antibody specifically binds to form a stronger acting force, the orientation of the LC molecules changes, resulting in a bright optical appearance. This LC-based immunosensor not only has the advantages of a facile structure, low cost and excellent specificity but also high sensitivity (a low detection limit of 1 pg ml-1), and has a promising future in biomedical related fields.

Multi-plane augmented reality display based on cholesteric liquid crystal reflective films.

To address the accommodation-convergence conflict problem in conventional augmented reality (AR) head-mounted displays, we propose a compact multi-plane display design based on cholesteric liquid crystal (CLC) reflective films and a polarization switch. Because of the polarization selectivity of CLC films, circularly-polarized light with different handedness is reflected by different CLC films, resulting in different optical path lengths and different image depths by the lens. A flicker-free dual-plane prototype with correct focus cues and relatively low operating voltage has been implemented. Moreover, a multi-plane AR display scheme with more than 2 depth planes is proposed by stacking multiple CLC films and polarization switches together.

Transflective spin-orbital angular momentum conversion device by three-dimensional multilayer liquid crystalline materials.

In this paper, a liquid crystal device for generating transflected optical vortices with high efficiency based on Pancharatnam-Berry phase is devised and demonstrated experimentally. In the experiment, both photo-alignment material and polymer-alignment material are used for assembling three-dimensional distributed liquid crystal polymer and cholesteric liquid crystal. Through the interaction between the incident light and the device, both transmitted light and reflected light get spin-orbital angular momentum conversion. Moreover, the amount of transmitted and reflected beams can be modulated by the input polarization. In our proposal, the device is dual functional, low-cost and simple in manufacturing process.

Orthogonal reactivity of Ni(i)/Pd(0) dual catalysts for Ullmann C-C cross-coupling: theoretical insight.

Dual catalysis has become a desirable alternative because of the synergetic effect of two distinct catalysts, but little is known about the mechanism of dual catalysis and its effect on the high reactivity and selectivity. Here, a novel Ullmann C-C cross-coupling of bromobenzene and 4-methoxyphenyltriflate via nickel/palladium dual catalysis has been investigated using density functional theory. The orthogonal reactivity of NiI/Pd0 combination is the precondition and foundation of achieving such a Ullmann cross-coupling reaction. In the present dual catalysis, the NiI complex acts as the primary catalyst, while the Pd0 catalyst plays a decisive role in the cross-selectivity.

[A Study of Lasing Spectrum of Dye-Doped Chiral Nematic Liquid Crystal Cell under Electric Field].

The lasing spectrum of dye-doped chiral nematic liquid crystal under electric filed was investigated. Two kinds of electrodes were designed to apply transverse electric field to positive liquid crystal cell and longitudinal electric field to negative liquid crystal cell. A 532 nm Nd∶YAG pulsed solid-state laser was used to pump the cell. When transverse electric field is applied to positive liquid crystal device, multi-wavelength laser output is obtained in the range of 630~660 nm. When longitudinal electric field is applied to negative liquid crystal cell, 18.5 nm tunable output lasing is obtained. The output characteristic of cell was analyzed from the texture of device and the photonic band gap. In the positive liquid crystal cell, the competition of electric moment with twisting moment causes the flow of LC molecule, and the flow of LC molecule leads to a floating photonic band gap. For this reason, not only at the edge of photonic band gap but in the photonic band gap can produce lasing. For negative liquid crystal cell, the pitch shrinks with the increase of electric field. The photonic band gap shows blue-shift with the decrease of pitch. and Lasing wavelength is blue shifted from 681.0 to 662.5 nm and the lasing at the edge of photonic band gap. Negative liquid crystal cell has better stability under electric field effect.

Optimal energy-splitting method for an open-loop liquid crystal adaptive optics system.

A waveband-splitting method is proposed for open-loop liquid crystal adaptive optics systems (LC AOSs). The proposed method extends the working waveband, splits energy flexibly, and improves detection capability. Simulated analysis is performed for a waveband in the range of 350 nm to 950 nm. The results show that the optimal energy split is 7:3 for the wavefront sensor (WFS) and for the imaging camera with the waveband split into 350 nm to 700 nm and 700 nm to 950 nm, respectively. A validation experiment is conducted by measuring the signal-to-noise ratio (SNR) of the WFS and the imaging camera. The results indicate that for the waveband-splitting method, the SNR of WFS is approximately equal to that of the imaging camera with a variation in the intensity. On the other hand, the SNR of the WFS is significantly different from that of the imaging camera for the polarized beam splitter energy splitting scheme. Therefore, the waveband-splitting method is more suitable for an open-loop LC AOS. An adaptive correction experiment is also performed on a 1.2-meter telescope. A star with a visual magnitude of 4.45 is observed and corrected and an angular resolution ability of 0.31″ is achieved. A double star with a combined visual magnitude of 4.3 is observed as well, and its two components are resolved after correction. The results indicate that the proposed method can significantly improve the detection capability of an open-loop LC AOS.

Theory and characteristics of holographic polymer dispersed liquid crystal transmission grating with scaffolding morphology.

We have performed a detailed characterization of the optical properties of a holographic polymer dispersed liquid crystal (LC) transmission grating with polymer scaffolding morphology, which was fabricated with conventional high-functionality acrylate monomer under low curing intensity. Temporal evolution of the grating formation was investigated, and the amount of phase-separated LC was determined by birefringence investigation. A grating model combined with anisotropic coupled-wave theory yielded good agreement with experimental data without any fitting parameter. The results in this study demonstrate the non droplet scaffolding morphology grating is characterized by a high degree of phase separation (70%), high anisotropy, low scattering loss (<6%), and high diffraction efficiency (95%).

Improvement of the switching frequency of a liquid-crystal spatial light modulator with optimal cell gap.

In the application of a nematic liquid-crystal (LC) spatial light modulator, we derived the formula of retardation dynamic response of the device by solving the Erickson-Leslie equation. Then, the response time of the 2π phase change can be expressed as a function of the LC cell gap. The theoretical and experimental results all indicate that the response time of 2π first decreases and then increases with the LC cell gap increasing, and there is an optimal cell gap to obtain the shortest response time. Therefore, the method of optimizing the cell gap shows potential to improve the switching frequency for all type of nematic LC optical device with specific modulation quantity.

[Spectral studies on liquid crystal photoalignment film of photosensitive monomer with fluorinated groups].

2, 2, 3, 3, 4, 4-hexafluoro-1,5-pentanediol dicinnamate ester, which could be crosslinked under irradiation of linearly polarized ultraviolet light, was synthesized in the present work. UV-Visible spectra and FTIR spectra revealed that [2+2] cycloaddition was the main reaction of the monomer, but there was no clear morphological anisotropy on the surface of the obtained photoalignment film through atomic force microscopic analysis. The photoalignment film could induce homogenous alignment of liquid crystal and the alignment is uniform. It was found that the pretilt angle of the photoalignment film is 1 degrees-2 degrees.