Inorganic Liquid Crystals Research Articles

Preparation and optical properties of one-dimensional magnetically oriented halloysite@Fe3O4 nanomaterials

Clay minerals with composite magnetic particles offer potential as magnetically oriented nanomaterials for application in inorganic liquid crystals. However, the instability of magnetically oriented clay@Fe3O4 materials, caused by the easy detachment of Fe3O4 particles from the clay minerals surfaces and the corrosivity of the HCl dispersant on Fe3O4 particles, has limited their development. In this work, hollow tubular halloysite (Hal) was used as the carrier for Fe3O4 particles to obtain halloysite@Fe3O4 (Hal@Fe3O4), in which Fe3O4 particles were uniformly coated on the outer surface of Hal and located in the Hal tubular lumen. In addition, LiCl was employed as a dispersant instead of HCl in Hal@Fe3O4 dispersions. They collaboratively enhanced the stability of magnetically oriented Hal@Fe3O4 nanomaterials compared to magnetically oriented palygorskite@Fe3O4 nanomaterials. The stable one-dimensional magnetically oriented Hal@Fe3O4 nanomaterials demonstrated liquid crystal properties that were adjustable by a magnetic field, and photonic crystal properties. As a result, these functional materials could be used in many fields, such as inorganic liquid crystals, photonic crystals, and photonic switches.

Exploring Colloidal Phase Transitions of Imogolite Nanotubes by Evaporation Induced Self‐Assembly in Levitation

AbstractEvaporation‐induced self‐assembly (EISA) is a versatile method for generating organized superstructures from colloidal particles, offering diverse design possibilities through the manipulation of colloid size, shape, substrate nature, and environmental conditions. While some work highlighted the potential of EISA to investigate phase transitions of inorganic liquid crystals, the influence of sample environment to determine their phase diagrams is often overlooked. In this work, the self‐assembly of lyotropic liquid crystals is compared by EISA on substrates, and by acoustic levitation (absence of substrate). The focus is on imogolite nanotubes, a model colloidal system of 1D charged objects, due to their tunable morphology and rich liquid‐crystalline phase behavior. It demonstrates the feasibility to obtain phase transitions in levitating droplets and on soft hydrophobic substrates, whereas self‐assembly is limited on rigid hydrophilic supports. Moreover, the aspect ratio of the nanotubes proves to be a pivotal factor, influencing both transitions and the resulting materials shape and surface. Besides material shaping, acoustic levitation emerges as a promising method for studying phase transitions by EISA, toward the rapid establishment of phase diagrams from diluted to highly concentrated states using a limited volume of sample.

Introduction of CdSe/ZnS Quantum Dots into Liquid Crystalline Matrix

An important aspect of modern materials science, namely the possibility of combining inorganic nanoparticles and liquid crystals in composite materials is discussed. These systems make it possible to combine liquid crystal properties of matrix and luminescent properties of quantum dots. A five-component mixture consisting mainly of 4-cyanobiphenyl derivatives used as a matrix. The substitution of ligands formed during the synthesis of quantum dots with derivatives of organic acids is shown. Using two new optically active ligands, the chiralization of the nematic matrix was demonstrated by introducing quantum dots into it.

Multimodal-Responsive Circularly Polarized Luminescence Security Materials.

Nations, industries, and aspects of everyday life have undergone forgery and counterfeiting ever since the emergence of commercialization. Securing documents and products with anticounterfeit additives shows promise for authentication, allowing one to combat ever-increasing global counterfeiting. One most-used effective encryption strategy is to combine with optical-security markers on the required protection objects; however, state-of-the-art labels still suffer from imitation due to their poor complexity and easy forecasting, as a result of deterministic production. Developing advanced anticounterfeiting tags with unusual optical characters and further incorporating complex security features are desired to achieve multimodal, unbreakable authentication capacity; unfortunately, this has not yet been achieved. Here, we prepare a series of stable circularly polarized luminescence (CPL) materials, composed of toxicity-free, high-quality-emitting inorganic quantum dots (QDs) and liquid crystals, using a designed helical-coassembly strategy. This CPL system achieves a figure of merit (FM, assessing the performance of both luminescence dissymmetry and quantum yield) value of 0.39, fulfilling practical demands for anticounterfeiting applications. Based on these CPL structures, we produce a type of multimodal-responsive security materials (MRSMs) that exhibits six different stimuli-responsive modes, including light activation, polarization, temperature, voltage, pressure, and view angle. Thus, we show a proof-of-principle blockchain-like integrated anticounterfeiting system, allowing multimodal-responsive, interactive/changeable information encryption-decryption. We further encapsulate the obtained security materials into a fiber to expand our materials to work on flexible fabrics, that is, building an intelligent textile with a color-adaptable function along with environmental change.

2D material inorganic liquid crystals for tunable deep UV light modulation.

2D material inorganic liquid crystals for tunable deep UV light modulation.

2D Functional Minerals as Sustainable Materials for Magneto‐Optics (Adv. Mater. 16/2022)

Sustainable Optics Ores are everywhere on our earth and other planets, and many of them possess layered structures. In article 2110464, Baofu Ding, Bilu Liu, and co-workers develop a seawater-assisted green method to produce 2D minerals in large quantities from bulky ores. These 2D minerals are used as inorganic liquid crystals for color optics. This work creates novel opportunities of using abundant naturally minerals for advanced technological applications.

2D Functional Minerals as Sustainable Materials for Magneto-Optics.

Liquid crystal devices using organic molecules are nowadays widely used to modulate transmitted light, but this technology still suffers from relatively weak response, high cost, toxicity and environmental concerns, and cannot fully meet the demand of future sustainable society. Here, an alternative approach to color-tunable optical devices, which is based on sustainable inorganic liquid crystals derived from 2D mineral materials abundant in nature, is described. The prototypical 2D mineral of vermiculite is massively produced by a green method, possessing size-to-thickness aspect ratios of >103 ,in-plane magnetization of >10emu g-1 , and an optical bandgap of >3eV.These characteristics endow 2D vermiculite with sensitive magneto-birefringence response, been several orders of magnitude larger than organic counterparts, as well as capability of broad-spectrum modulation. The finding consequently permits the fabrication of various magnetochromic or mechanochromic devices with low or even zero-energy consumption during operation. This work creates opportunities for the application of sustainable materials in advanced optics.

Amplifying inorganic chirality using liquid crystals.

Chiral inorganic nanostructures have drawn extensive attention thanks to their unique physical properties as well as multidisciplinary applications. Amplifying inorganic chirality using liquid crystals (LCs) is an efficient way to enhance the parented inorganic asymmetry owing to chirality transfer. Herein, the universal synthetic methods and structural characterizations of chiral inorganic-doped LC hybrids are introduced. Additionally, the current progress and status of recent experiment and theory research about chiral interactions between inorganic nanomaterials (e.g. metal, semiconductor, perovskite, and magnetic oxide) and LCs are summarized in this review. We further present representative applications of these new hybrids in the area of encryption, sensing, optics, etc. Finally, we provide perspectives on this field in terms of material variety, new synthesis, and future practice. It is envisaged that LCs will act as a pivotal part in the amplification of inorganic chirality with versatile applications.

Collective Behavior Induced Highly Sensitive Magneto-Optic Effect in 2D Inorganic Liquid Crystals.

Collective behavior widely exists in nature, ranging from the macroscopic cloud of swallows to the microscopic cloud of colloidal particles. The behavior of an individual inside the collective is distinctive from its behavior alone, as it follows its neighbors. The introduction of such collective behavior in two-dimensional (2D) materials may offer new degrees of freedom to achieve desired but unattained properties. Here, we report a highly sensitive magneto-optic effect and transmissive magneto-coloration via introduction of collective behavior into magnetic 2D material dispersions. The increase of ionic strength in the dispersion enhances the collective behavior of colloidal particles, giving rise to a magneto-optic Cotton-Mouton coefficient up to 2700 T-2 m-1 which is the highest value obtained so far, being 3 orders of magnitude larger than other known transparent media. We also reveal linear dependence of magneto-coloration on the concentration and hydration ratios of ions. Such linear dependence and the extremely large Cotton-Mouton coefficient cooperatively allow fabrication of giant magneto-birefringent devices for color-centered visual sensing.

Optimization of Chemical Structure of Compatibilizers Based on Liquid Crystalline Diblock Copolymers for Reconciliation Between Inorganic Quantum Dots and Organic Cholesteric Liquid Crystals

Optimization of Chemical Structure of Compatibilizers Based on Liquid Crystalline Diblock Copolymers for Reconciliation Between Inorganic Quantum Dots and Organic Cholesteric Liquid Crystals

Novel thermochromic (TC) and electrochromic (EC) characteristics of the V4O7 liquid crystal for LCDs and versatile optoelectronic applications

To form an electrochromic cell, the chemical reaction procedures were obeyed to prepare the V4O7 crystal suspended in a strong electrolytic HCl solution. Some of these suspended V4O7 crystals were injected between two sealed parallel ITOs/glass' slabs to construct an optoelectronic cell. A spray system technique was used to deposit the residue of the V4O7 solution as thin-film over glass' slabs. X-ray diffraction pattern (XRD), Field Emission Scanning electron microscopy (FESEM) with Energy Dispersive Analysis X-Ray (EDAX), and optical characterizations were used to inspect the obtained crystals. The structural investigations confirmed the hexagonal crystalline nature of the V4O7 crystal. The thermochromic (TC) and the electrochromic (EC) measurements showed that the studied V4O7 liquidus crystals have high sensitivity for the external either heat or the applied electric field. The applied thermal and electrical influences caused the direct optical band gap to change from 3.8 eV to 3.98 and 4.03 eV under EC and TC tests, respectively. The third-order nonlinear optical susceptibilities reached their maxima about 4.4 × 10−11 esu and 5.9 × 10−11 esu under TC and EC effects. The nonlinear refractive index was varied till reached 5.26 × 10−10 and 6.91 × 10−10 under TC and EC, respectively. Such properties plus optoelectronic response time about 1.5 mSec and high stability all qualifies this inorganic cell to be nominate for light modulation applications, i.e., optical filters, inorganic liquid crystals display (LCD), smart windows, optical switching, and optical fibers.

Smectic Liquid Crystalline Titanium Dioxide Nanorods: Reducing Attractions by Optimizing Ligand Density

AbstractCrystalline titanium dioxide (TiO2) semiconductor nanorods (NRs) feature several optical properties, such as birefringence combined with high refractive indexes and a wide bandgap precluding optical absorption in visible‐light spectrum, making them attractive for many applications such as optoelectronics. Dispersing these NRs in suitable solvents creates inorganic liquid crystals (LCs) offering enhanced collective and orientation‐dependent properties, which can additionally be utilized to manipulate optical behavior. Herein, a synthetic procedure from literature is scaled up and coupled with an important post‐synthesis‐treatment step such that self‐assembled NRs dried onto a liquid interface and in bulk can be investigated. Comprehensive characterizations confirm the vital role of surface ligand density of the NRs in reducing the effects of attractions between them and thus increasing the range of volume fractions in which these dispersions can be exploited. Various symmetries (hexagonal or tetragonal) can be achieved in the smectic layers of NRs by tuning the aspect ratios of the NRs from 4.8 to 8.5. Experiments show that external fields such as shear flow or electric fields can easily either induce a reversible nematic order in isotropic dispersions or order existing LC phases over much longer regions, opening many opportunities to manipulate light for optical applications.

Non-aqueous liquid crystals of hydroxyapatite nanorods

Hydroxyapatite (HA) nanorods in the collagen matrix of bone have a macroscopically ordered structure that has many similarities to the ordered structure of anisotropic nano-units in inorganic liquid crystals (LCs). Inspired by these similarities, we conducted the first (to our best knowledge) synthesis of HA LCs in non-polar solvents (such as cyclohexane and toluene), thus expanding the range of applicable monomers and polymers. We synthesized HA nanorods by a simple, effective, and oleic-acid-assisted hydrothermal route. The hydrothermal temperature directly modulates the aspect ratio of the HA nanorods, and indirectly modulates their LC behavior. The LC phase transition has no size limitation. Thus, our approach may be used to develop high solid content, macroscopically assembled, large-scale polymer-based bio(mimetic)-materials.

Novel Trends in Lyotropic Liquid Crystals

We introduce and shortly summarize a variety of more recent aspects of lyotropic liquid crystals (LLCs), which have drawn the attention of the liquid crystal and soft matter community and have recently led to an increasing number of groups studying this fascinating class of materials, alongside their normal activities in thermotopic LCs. The diversity of topics ranges from amphiphilic to inorganic liquid crystals, clays and biological liquid crystals, such as viruses, cellulose or DNA, to strongly anisotropic materials such as nanotubes, nanowires or graphene oxide dispersed in isotropic solvents. We conclude our admittedly somewhat subjective overview with materials exhibiting some fascinating properties, such as chromonics, ferroelectric lyotropics and active liquid crystals and living lyotropics, before we point out some possible and emerging applications of a class of materials that has long been standing in the shadow of the well-known applications of thermotropic liquid crystals, namely displays and electro-optic devices.

Organic-inorganic hybrid liquid crystals of azopyridine-enabled halogen-bonding towards sensing in aquatic environment.

In this study, organic–inorganic hybrid mesogens of silver nanoparticles (Ag NPs) and azopyridines (AzoPys) enabled by halogen bonding were prepared. Triple functions of the degree of orientation change, metal-enhanced fluorescence, and surface-enhanced Raman scattering were observed in Ag⋯Br–Br⋯AzoPy nanoparticles (12Br–Ag), which were induced by the in situ synthesis of Ag NPs in AzoPy. The bromine molecules were then linked by halogen bonding and electrostatic interaction resulting in the smectic A phase of 12Br–Ag. To demonstrate the potential of Br–Br⋯AzoPy (12Br) as a practical sensor, we used the 12Br compound to detect silver in an aqueous condition, and significant signals of the halogen-bonded complex-silver system were observed in the X-ray diffraction pattern and Raman spectra. Herein, we provide a novel perspective and design principle for the practical applications of organic–inorganic hybrid liquid crystals in environmental monitoring.

Bio-Inspired Synthesis of Non-Aqueous Liquid Crystals of Hydroxyapatite Nanorods

Hydroxyapatite (HA) nanorods in the collagen matrix of bone have a macroscopically ordered structure that has many similarities to the ordered structure of anisotropic nano-units in inorganic liquid crystals (LCs). Inspired by these similarities, we conducted the first (to our best knowledge) synthesis of HA LCs in non-polar solvents (such as cyclohexane and toluene), thus expanding the range of applicable monomers and polymers. We synthesized HA nanorods by a simple, effective, and oleic-acid-assisted hydrothermal route. The hydrothermal temperature directly modulates the aspect ratio of the HA nanorods, and indirectly modulates their LC behavior. The LC phase transition has no size limitation. Thus, our approach is a unique platform for developing high solid content, macroscopically assembled, large-scale polymer-based bio(mimetic)-materials.

Bio-inspired synthesis of aqueous nanoapatite liquid crystals

The macroscopically ordered structure of rod-like nanoapatites within the collagen matrix is of great significance for the mechanical performance of bones and teeth. However, the synthesis of macroscopically ordered nanoapatite remains a challenge. Inspired by the effect of citrate molecules on apatite crystals in natural bone and the similarities between these ordered rod-like nanoapatites and the nematic phase of inorganic liquid crystals (LCs), we synthesized aqueous liquid crystal from rod-like nanoapatites with the aid of sodium citrate. Following a similar procedure, aqueous Mg(OH)2 and Mg3(PO4)2 LCs were also prepared. These findings lay the foundation for the fabrication of macroscopically assembled nanoapatite-based functional materials for biomedical applications and offer a green chemical synthesis platform for the development of new types of inorganic LCs. This process may reduce the difficulties in synthesizing large quantities of inorganic LCs so that they can be applied to the fabrication of functional materials.

3a04 極性有機溶媒分散型無機ナノシート液晶の物性・構造に対する微量の塩および水の影響(ソフトマター,口頭発表,2012年日本液晶学会討論会)

3a04 極性有機溶媒分散型無機ナノシート液晶の物性・構造に対する微量の塩および水の影響(ソフトマター,口頭発表,2012年日本液晶学会討論会)

Inorganic gel and liquid crystal based smart window using silica sol-gel process

A controllable transparent device using an inorganic glass gel-dispersed liquid crystal (GDLC) was fabricated using the sol-gel method to overcome the limitations of conventional polymer-dispersed liquid crystals, such as haziness and yellowing. In this study, silica gel and titanium dioxide acted as a matrix holding the liquid crystal droplets, and the optical properties of the proposed GDLC were then studied in a silica solution by mixing tetra ethyl ortho-silicate, methyltriethoxysilane, isopropyl alcohol, and nitric acid in an aqueous solution. A titanium solution with titanium isopropoxide and acetylacetone was also mixed with the silica solution, with the further addition of a nematic liquid crystal. A parameter study was carried out by varying the concentration to obtain the best sample, with fast response times of ~0.5 and 3ms, respectively for the on and off processes, high contrast, and low haziness when compared with previously reported results. The GDLC samples exhibited low scattering, a clear colorless state, and a low driving voltage, which are all very important advantages for applications. For demonstration, our glass-based smart window was also applied as a rear-view mirror in a vehicle for anti-dazzling purposes at night, which has not been reported by others.

Успехи в изучении неорганических лиотропных жидких кристаллов

Успехи в изучении неорганических лиотропных жидких кристаллов