Carbon dots stabilized photoluminescent blue phase liquid crystals.

Blue phase liquid crystals (BPLCs) have significant potential in the field of liquid crystal displays (LCDs) and are proposed as potential next-generation of LCDs candidates. However, BPLCs do not emit light directly and need an extra backlight device. As a result, the blue phase liquid crystal display retains the disadvantages of low brightness and low energy efficiency, which remarkably limit its application. Recently, as a kind of novel fluorescent carbon nanomaterials, carbon dots (CDs) have captured considerable attention because of their excellent optical properties. Here, CDs were directly synthesized by a simple solvothermal method and introduced into BPLCs. By combining the excellent optical properties of CDs with the blue phase liquid crystal system, the photoluminescent blue phase liquid crystals (CDs-BPLCs) with self-photoluminescence are prepared. Meanwhile, the stability of BPLCs can be improved by CDs. Such CDs-BPLCs have enormous potential in the development of novel energy-saving display devices.

High-Throughput Preparation and High-Throughput Detection of Polymer-Dispersed Liquid Crystals Based on Ink-Jet Printing and Grayscale Value Analysis.

In this paper, based on high-throughput technology, polymer dispersed liquid crystals (PDLC) composed of pentaerythritol tetra (2-mercaptoacetic acid) (PETMP), trimethylolpropane triacrylate (TMPTA), and polyethylene glycol diacrylate (PEGD 600) were investigated in detail. A total of 125 PDLC samples with different ratios were quickly prepared using ink-jet printing. Based on the method of machine vision to identify the grayscale level of samples, as far as we know, it is the first time to realize high-throughput detection of the electro-optical performance of PDLC samples, which can quickly screen out the lowest saturation voltage of batch samples. Additionally, we compared the electro-optical test results of manual and high-throughput preparation PDLC samples and discovered that they had very similar electro-optical characteristics and morphologies. This demonstrated the viability of PDLC sample high-throughput preparation and detection, as well as promising application prospects, and significantly increased the efficiency of PDLC sample preparation and detection. The results of this study will contribute to the research and application of PDLC composites in the future.

Multilayer, Broadband Infrared Reflectors Based on the Photoinduced Preparation of Cholesteric Liquid Crystal Polymers.

This paper focuses on preparing broadband reflective liquid crystal films through the diffusion of monofunctional and bifunctional monomers in a photoinduced trilayer system. By combining the hydrophilic and hydrophobic liquid crystal glass surface treatment technologies, the polymer network of polymer-stabilized cholesteric liquid crystal (PSCLC) itself serves as a diffusion channel to form a trilayer cholesteric liquid crystal composite system containing bifunctional monomers, a nematic liquid crystal composite system, and a cholesteric liquid crystal composite system containing monofunctional monomers. Utilizing the difference in the polymerization rates of monofunctional and difunctional polymerizable monomers, the monomers and chiral compounds diffuse relative to each other, so that the liquid crystal pitch exhibits a gradient distribution, and the broadened reflective width can reach up to 1570 nm. There is no doubt that new and improved processes and technologies offer important possibilities for preparing and applying PSCLC films.

Optical properties of broadband reflection of cholesteric liquid crystal by thermal diffusion of benzotriazoles.

Polymer stabilized cholesteric liquid crystal broadband reflective films are prepared by the thermal diffusion of a benzotriazoles organic ultraviolet (UV) absorber (UV-327) combined with photopolymerization. A gradient of UV intensity is established in the direction of film thickness, inducing the formation of a pitch gradient distribution, thus broadening the reflected bandwidth. The effects of UV-327 concentration, UV irradiation intensity, irradiation time, polymerization temperature, and C6M concentration on the reflected bandwidth of the sample are examined in detail. The results indicate that the diffusion method of the organic UV absorber enables the reflected bandwidth to be broadened under appropriate conditions.

Research Progress of Cholesteric Liquid Crystals with Broadband Reflection.

Cholesteric liquid crystal (ChLC) materials with broadband reflection are witnessing a significant surge in interest due to their unique ability to self-organize into a helical supra-molecular architecture and their excellent selective reflection of light based on the Bragg relationship. Nowadays, by the virtue of building self-organized nanostructures with pitch gradient or non-uniform pitch distribution, extensive work has already been performed to obtain ChLC films with a broad reflection band. This critical review systematically summarizes the optical background of the ChLCs with broadband reflection characteristics, methods to obtain broadband reflection of ChLCs, as well as the application in this area. Combined with the research status and the advantages in the field, the challenges and opportunities of applied scientific problems in the research direction are also introduced.

Spatial Patterning of Fluorescent Liquid Crystal Ink Based on Inkjet Printing.

Fluorescent cholesteric liquid crystal materials (FCLC) with aggregation-induced emission (AIE) properties can effectively solve the contradiction between aggregation-induced quenching (ACQ) and liquid crystal self-assembly when light-emitting materials are aggregated, and they have great application value in the fields of anti-counterfeit detection and information hiding. However, generating a visually appealing design, logo, or image in the application typically requires an intricate fabrication process, such as the use of prefabricated molds and photomasks, which greatly limits the practical application of FCLC materials. Herein is reported a new method for spatially patterned liquid crystal (LC) microdroplet arrays using drop-on-demand inkjet printing technology. Through rational composition design, a spatial array composed of different liquid crystal microdroplets was established, and the array contains two entirely distinct but intact patterns at the same time, which can be reversibly switched under the irradiation of UV and natural light. This study provides a new method for the integrated preparation of different component liquid crystal materials.

High-Throughput Preparation and Machine Learning Screening of a Blue-Phase Liquid Crystal Based on Inkjet Printing.

Blue-phase liquid crystal (BPLC) is considered as the next-generation liquid crystal display material, but its practical application is seriously affected by a narrow temperature range and a long research period. In this paper, we used inkjet printing technology to prepare BPLC materials with high throughput, and try to use machine vision technology to test BPLC with high throughput. The "standard curve method" for establishing each printing channel and the "vector matching method" for searching the chromaticity value of the minimum distance were proposed to improve the accuracy of inkjet printing BPLC materials. For a large number of sample-phase images, we propose a machine learning method to identify the liquid crystal phase. In this paper, for the first time, the high-throughput preparation and high-throughput detection of 1080 BPLC samples with five common components by a comprehensive experimental method has been successfully realized. The results are helpful to improve the research efficiency of blue-phase materials and provide a theoretical basis and practical guidance for rapid screening of multi-component BPLC materials.

H-Bonding Room Temperature Phosphorescence Materials via Facile Preparation for Water-Stimulated Photoluminescent Ink.

Pure organic room-temperature phosphorescence (RTP) materials built upon noncovalent interactions have attracted much attention because of their high efficiency, long lifetime, and stimulus-responsive behavior. However, there are limited reports of noncovalent RTP materials because of the lack of specific design principles and clear mechanisms. Here, we report on a noncovalent material prepared via facile grinding that can emit fluorescence and RTP emission differing from their components' photoluminescent behavior. Exciplex can be formed during the preparation process to act as the minimum emission unit. We found that H-bonds in the RTP system provide restriction to nonradiative transition but also enhance energy transformation and energy level degeneracy in the system. Moreover, water-stimulated photoluminescent ink is produced from the materials to achieve double-encryption application with good resolution.

Highly Efficient Spin-Filtering Transport in Chiral Hybrid Copper Halides.

Chiral Pb(Sn)-I hybrid organic-inorganic perovskites exhibit outstanding chiral-induced spin selectivity (CISS) performance, but the nontoxic lead-free hybrid materials with high stability are still greatly desired for spin filtering in spintronic applications. We synthesize chiral hybrid copper halides (R/S-MBA)2 CuX4 (MBA=methylbenzylammonium; X=Cl, Br) with characteristic 0D CuX4 tetrahedral structural motifs, combining the low toxicity of Cu2+ and air stability of halide ions (Cl- and Br- ). Despite similar structural and electronic features, (R/S-MBA)2 CuBr4 shows much smaller chiroptical activity than the chloride counterpart. Magnetically conductive atomic force microscopy measurements display a typical spin-polarized charge-transport property with high efficiency up to 90 % for both copper halides. Our work expands the CISS effect into eco-friendly and stable metal-organic halides, which is promising for applications in spintronics based on transition-metal hybrid systems.

The application of small organic π-conjugated discotic derivatives in photoacoustic imaging and photothermal conversion.

Near-infrared absorbing dyes are catching people's attention as they are committed to find materials with greater photoacoustic (PA) and photothermal (PT) effect. In this study, a new series of organic π-conjugated discotic derivatives synthesized via [2 + 2] click chemistry were introduced. The PA intensity and PT conversion effect of the derivatives were monitored. It was found that the π-conjugated discotic derivatives had a proper absorption peak and PA intensity by introducing the click regents. Furthermore, the PA intensity remained relatively high, while B12 molecules were embedded in hydrophobic phospholipid bilayer of liposomes (B12⊂L). The application in biological therapy for tumors become possible as the toxicity of B12⊂L was low. What's more, when B12 molecules embedded in poly (N-isopropylacrylamide)-block-poly (2-nitrobenzyl methacrylate) (PNIPAM-b-PNBM) thermosensitive micelles were irradiated by laser, the molecules could take the place of direct temperature stimulus. This work affords us a way to solve the problem in which direct temperature stimulus is inapplicable.

Reversible solvent-sensitive actuator with continuous bending/debending process from liquid crystal elastomer-colloidal material.

A reversible solvent-sensitive actuator with a continuous bending/debending process is fabricated by over-infiltration of liquid crystal monomers into a colloidal template and subsequent photopolymerization. The fabricated actuator exhibits a maximum bending angle of 1080° in 1.58 s in dichloromethane, accompanied with successive debending in 0.32 s. The behavior of the actuator can be modulated by changing the solvent type, film thickness/length and molar ratio of A6OCB/C6M. This study will provide an important experimental and theoretical basis for the development of novel actuators.

Broadband reflection in polymer stabilized cholesteric liquid crystal films with stepwise photo-polymerization.

In this study, we demonstrate a novel method for fabricating polymer stabilized cholesteric liquid crystal (PSCLC) films with non-uniform pitch distribution by utilizing two kinds of photo-induced processes. Based on the large HTP temperature dependence of a chiral dopant, polymer networks were formed at two distant temperature points in sequence. The influence of the polymerization conditions on the reflectance properties of PSCLCs before and after polymerization was investigated. The results strongly suggest that the location and bandwidth of the reflection band can be controlled preferably by adjusting the ultraviolet light intensity and irradiation time of UV-light. In addition, the morphology of the polymer network in the composites was studied using scanning electron microscopy (SEM). A general correlation between polymerization conditions, the network morphology, and the reflective region will be outlined.

Click chemistry functionalization improving the wideband optical-limiting performance of fullerene derivatives.

A novel kind of monodonor-bisacceptor (D-A-A) C60 charge-transfer complex was synthesized by the high-yielding [2+2] click chemistry reaction and the Prato reaction. Both electrochemical and UV-vis spectra studies were carried out and they proved that the side groups of the fullerene derivatives played an important role in the energy gaps, and also affected the third-order non-linear optical response. The experimental investigation on the third-order non-linear optical phenomena of the fullerene derivatives was measured using the Z-scan technique at different wavelengths (532 nm and 1064 nm). All the compounds exhibited very special non-linear optical properties when pumped by 21 ps pulses at 532 nm which suggested that there were two different types of reversible photo-isomerization. The optical-limiting performance has also been studied which proved indirectly the mechanism models of the reversible photo-isomerization.

Preparation and optical properties of Fe3O4 nanoparticles-doped blue phase liquid crystal.

The magnetic Fe3O4 nanoparticle-doped blue phase liquid crystal (BPLC) was found to have a relatively strong contrast ratio in magnetic-addressed display performance compared to the composites in other phases; this is a new application of the BPLC and a way to prepare a new type of power-free magnetically-driven LC flexible display.

Optoelectronic and self-assembly properties of porphyrin derivatives with click chemistry modification.

A series of functionalized porphyrin molecules containing electron-rich alkynes, synthesized by means of the Sonogashira coupling reaction were further modified by reacting the ethynyl groups with click reagent through a formal [2+2] click reaction. The photophysical and electrochemical properties of the porphyrin derivatives were studied by UV/Vis spectroscopy and cyclic voltammetry. We show that the optoelectronic properties are affected by the click reagent groups and central metal ions. The functionalized porphyrin molecules show strong charge-transfer (CT) bands in the visible region (near-IR region) and potent redox activities. Through a phase-exchange self-assembly method, the highly organized morphologies were observed by scanning electron microscopy (SEM). The functionalized porphyrin molecules represent an interesting set of candidates for optoelectronic device components. The effect of the metal ions or click reagent groups on the self-assembly properties were also studied by the UV/Vis spectroscopic titration experiments.

Flexible H-bonded liquid-crystals with wide enantiotropic blue phases.

Novel cinnamic-acid-derived H-bonded liquid crystals with enantiotropic BP*s were facilely prepared. When simply modifying the donor-acceptor ratio, the proportion of (S)-4-(2-octanyloxy) cinnamic acid to 4-(4-propylcyclohexyl) phenyl isonicotinate, the generated BP temperature ranges were consequentially extended with the widest range of about 10 °C, which is seldom found in enantiotropic BP materials. The optimized results of density-functional-theory calculations show that cinnamic-acid-derived mesogens have a bent shape and thus could be beneficial to stabilize enantiotropic blue phases.

Serum brain-derived neurotrophic factor levels in type 2 diabetes mellitus patients and its association with cognitive impairment: A meta-analysis.

OBJECTIVE: To compare the serum levels of brain-derived neurotrophic factor (BDNF) in type 2 diabetes mellitus (T2DM) patients with healthy controls (HC) and evaluate the BDNF levels in T2DM patients with/without cognitive impairment. METHODS: PubMed, EMBASE, and the Cochrane Library databases were searched for the published English literature on BDNF in T2DM patients from inception to December 2022. The BDNF data in the T2DM and HC groups were extracted, and the study quality was evaluated using the Agency for Healthcare Research and Quality. A meta-analysis of the pooled data was conducted using Review Manager 5.3 and Stata 12.0 software. RESULTS: A total of 18 English articles fulfilled with inclusion criteria. The standard mean difference of the serum BDNF level was significantly lower in T2DM than that in the HC group (SMD: -2.04, z = 11.19, P <0.001). Besides, T2DM cognitive impairment group had a slightly lower serum BDNF level compared to the non-cognitive impairment group (SMD: -2.59, z = 1.87, P = 0.06). CONCLUSION: BDNF might be involved in the neuropathophysiology of cerebral damage in T2DM, especially cognitive impairment in T2DM.

Insights into the circular: The cryptic plasmidome and its derived antibiotic resistome in the urban water systems.

Plasmids have been a concern in the dissemination and evolution of antibiotic resistance in the environment. In this study, we investigated the total pool of plasmids (plasmidome) and its derived antibiotic resistance genes (ARGs) in different compartments of urban water systems (UWSs) in three European countries representing different antibiotic usage regimes. We applied a direct plasmidome approach using wet-lab methods to enrich circular DNA in the samples, followed by shotgun sequencing and in silico contig circularisation. We identified 9538 novel sequences in a total of 10,942 recovered circular plasmids. Of these, 66 were identified as conjugative, 1896 mobilisable and 8970 non-mobilisable plasmids. The UWSs' plasmidome was dominated by small plasmids (≤10 Kbp) representing a broad diversity of mobility (MOB) types and incompatibility (Inc) groups. A shared collection of plasmids from different countries was detected in all treatment compartments, and plasmids could be source-tracked in the UWSs. More than half of the ARGs-encoding plasmids carried mobility genes for mobilisation/conjugation. The richness and abundance of ARGs-encoding plasmids generally decreased with the flow, while we observed that non-mobilisable ARGs-harbouring plasmids maintained their abundance in the Spanish wastewater treatment plant. Overall, our work unravels that the UWS plasmidome is dominated by cryptic (i.e., non-mobilisable, non-typeable and previously unknown) plasmids. Considering that some of these plasmids carried ARGs, were prevalent across three countries and could persist throughout the UWSs compartments, these results should alarm and call for attention.

Research Progress of Electrically Driven Multi-Stable Cholesteric Liquid Crystals.

Electrically driven multi-stable cholesteric liquid crystals can be used to adjust the transmittance of incident light. Compared with the traditional liquid crystal optical devices, the multi-stable devices only apply an electric field during switching and do not require a continuous electric field to maintain the various optical states of the device. Therefore, the multi-stable devices have low energy consumption and have become a research focus for researchers. However, the multi-stable devices still have shortcomings before practical application, such as contrast, switching time, and mechanical strength. In this article, the latest research progress on electrically driven multi-stable cholesteric liquid crystals is reviewed, including electrically driven multi-stable modes, performance optimization, and applications. Finally, the challenges and opportunities of electrically driven multi-stable cholesteric liquid crystals are discussed in anticipation of contributing to the development of multi-stable liquid crystal devices.

Near-Infrared Reflective Polymer Films Based on UV-327-Doped Zinc Oxide Nanoparticles.

We prepared cholesteric liquid crystal (CLC) films with broadband reflective properties by admixing organic dye UV-327 into inorganic zinc oxide nanoparticles (ZnO NPs), utilizing the principle of pitch distribution from a large to a small gradient along the film thickness direction, leading to broadband reflection. ZnO NPs are poorly dispersed and easy to gather, but they do not decompose easily. The addition of UV-327 makes up for the above shortcomings. UV-327 is an organic compound with good compatibility and dispersion with liquid crystal systems. Therefore, we used the method of mixing two UV-absorbing dyes (UV-327 and ZnO NPs) to obtain CLC films. UV-absorbing dyes (UV-327 and ZnO NPs) made the liquid crystal films form a UV intensity gradient in the direction of thickness, prompting the polymerizable monomers to polymerize faster on the stronger side of the light, leading to the relative diffusion of chiral molecules and polymerizable monomers, forming the concentration gradient of chiral molecules in the direction of thickness. The pitch has a gradient distribution as the chiral concentration varies. Then, anchored by the polymer network, the pitch gradient distribution no longer changes. Broadened reflective bandwidth can reach up to 881 nm. Furthermore, the film covers the near-infrared wavelength band well, which can be applied to future smart windows or laser shielding for medical and military applications. It is also believed that this achievement will optimize the preparation technology of broadband reflective CLC films in the future.