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Phase diagrams showing the dependence of the high temperature phases of CE8 on (a) C60, (b) SWCNT and (c) graphene oxide concentration. The uncertainty of the temperature measurements is of the order of the data points, $0.1 K. The solid lines are a guide to the eye.
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The thermal stabilization of blue phases is a subject that has been of scientific and technological interest since their discovery. Meanwhile, carbonaceous nanomaterials such as C60 fullerenes, carbon nanotubes and graphene have generated interdisciplinary interest spanning across solid-state physics, organic chemistry, colloids, all the way to sof...
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... ( Fig. 3(b), middle image). The addition of graphene oxide sheets to CE8 to rid the mixture of the N* phase to only observe a BP-SmA* phase sequence is seemingly more efficient than adding fullerenes, since it takes more than ten times the concentration by weight of fullerenes to completely form the BP phase at the expense of the N* phase (Fig. 4). In both cases, the temperature width of blue phases ceases to increase further with the addition of nanomaterials aer the BP-N*-SmA* triple point is observed. The SmA* phase is observed approximately 1 K higher in temperature as compared to the pure compound. In the case of the SWCNTs, the N* phase never completely disappears at any ...
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Citations
... Thermal stabilization is further improved by the inclusion of 0D fullerenes, 1D nanotubes, and 2D graphene oxide sheets [84], to name a few other examples. On the other hand, the use of CoPt nanoparticles allows the stabilization of one particular BP phase over the other two [85]. ...
Tunable circular devices made of liquid crystals or other materials, like lenses, axicons, or phase plates, are often constrained by limitations in size, tunability, power, and other parameters. These constraints restrict their use and limit their applicability. In this review, a thorough study of the use of light’s orbital angular momentum in the manufacturing of liquid crystal (LC) devices is presented. Twisted light fosters the simultaneous optimization of most critical parameters. Experimental demonstrations of the unmatched performance of tunable LC lenses, axicons, and other elements in parameters such as lens diameter (>1″), power and tunability (>±6 diopters), fill factor (>98%), and time response have been achieved by reversible vortex generation created by azimuthal phase delay. This phase delay can eventually be removed within the optical system so that lens performance is not affected.
... Further efforts showed the ways for various CLC-based materials, where doping with CNT allowed temperature-and irradiation-induced writing and erasing effects [175]. Carbon nanotubes were also reported to stabilize the "blue phase" as a promising phase state observed in cholesterics close to the isotropic transition [176]. Additionally, just to be mentioned-there are several reports of CNTs in more exotic media possessing cholesteric-like structures of molecular arrangements, such as DNA [177] or cellulose LCs [178]. ...
The current state of the study of different liquid crystalline (LC) systems doped with carbon nanotubes (CNTs) is discussed. An attempt is endeavored to outline the state-of-the-art technology that has emerged after two past decades. Systematization and analysis are presented for the integration of single- and multi-walled carbon nanotubes in thermotropic (nematic, smectic, cholesteric, ferroelectric, etc.) and lyotropic LCs. Special attention is paid to the effects of alignment and supramolecular organization resulting from orientational coupling between CNTs and the LC matrix. The effects of the specific inter-molecular and inter-particle interactions and intriguing microstructural, electromagnetic, percolation, optical, and electro-optical properties are also discussed.
... Because of the inhomogeneous electric field, the o and e rays bend and focus after passing through the biased PS-BPLC. Some new ways of demonstrating PS-BPLC consisting of nanoparticles are worthy of studying for the improvement of optical performance (Wang et al., 2013;Xu et al., 2015;Adam et al., 2020). Our calculated focal length is 11.6 cm based on the Kerr constant derived from the experimental data (Lin et al., 2010), which is close to the experimentally measured focal length of 13.1 cm. ...
The analytical distribution of the electric field in a micro-lens made of polymer-stabilized blue phase liquid crystals (PS-BPLCs) between two electrodes has been derived, and ray bending and focusing for the o (ordinary) and e (extraordinary) rays caused by the field-induced extended Kerr effect on the PS-BPLC have also been calculated. Those calculations show that the focal lengths of most o rays are longer than those of e rays. The o and e rays result in a focal length of 11.6 cm at a Kerr constant of 2.3768 nm/V ² close to the experimental data, and the calculated focal spot diameter is about 80.0 μm. If the Kerr constant is decreased to 2.14 nm/V ² , we can obtain a focal length of 13.1 cm, the same as the experimental data. This reduction in the Kerr constant is reasonable because it is still within the experimental error. In summary, our calculations reveal an efficient and accurate way to discuss the focusing phenomena in the PS-BPLC micro-lens.
... In fact, much work has been done on LC-nano composites inferring that NPs do play a key role in modifying the properties of LC including the phase transition temperatures [19,20]. Of relevance here are the observations that the thermal range of BP is influenced by composite systems consisting of polymers and LCs [10], dispersion of different types of nanoparticles and spherical/rod-shaped colloidal nanoparticles [9,14,21], as well as the combination of polymer-stabilization and addition of NPs [22]. Perturbation of the LC ordering around the NPs is envisaged to be the cause for the modification of the properties. ...
We report the influence of a small concentration (0.1 wt%) of ZnO nanoparticles (NPs) on the birefringence of the liquid crystal Blue phase. The measurements carried out using the field-induced birefringence technique show that the inclusion of NP diminishes the magnitude of the Kerr constant. We propose that the field-induced disclination networks act as trapping centres for the NPs and enhance the elastic constant leading to a diminution in the birefringence.
... However, the exploitation of BPs for technological purposes is severely constrained because of their narrow temperature range. Several strategies have been used to enlarge the BP range to make them viable for device applications like using mixtures of bimesogens and a helical twisting power agent; 13 using composite systems consisting of LCs and polymers; 14,15 incorporation of gold nanoparticles, 16 semiconductor nanocrystals, 17,18 and carbon nanotubes, 19 and doping with LCs made of achiral bent-core (BC) molecules. [20][21][22] BP LCs have attracted immense attention because of their possible use as tunable photonic bandgap materials. ...
Electro-optic and photonic devices that are robust against external stresses and deformation offer several technological advantages. A variety of device applications based on chiral liquid crystals (LCs) exhibiting blue phases (BPs), chiral nematic (N * ), and ferroelectric Smectic (SmC * ) phases have already been demonstrated. Chiral LC-gels are, therefore, among the best soft materials that can further extend device performance and functionality by combining electro-optic and photonic properties with mechanical stability. In view of this, a composite material composed of two highly chiral calamitic LCs and a low-molecular-weight organogelator was developed and investigated using a variety of experimental techniques. Optical microscopy, selective reflection, and x-ray diffraction studies show that the LC characteristics are very well retained in the chiral LC-gels, namely, BPIII-gel, BPII-gel, BPI-gel, N * -gel, twist grain boundary A phase (TGB A )-gel, and SmC * -gel, which form sequentially as the sample is gradually cooled from the isotropic phase. Rheological studies establish that the chiral LC-gels exhibit several features of a soft viscoelastic solid. This has been understood in terms of the mode of self-assembly of the gelator fibers and the ubiquitous defects pertinent to different LC phases. The major highlights of the study are the formation of a defect-mediated strong N * -gel with enhanced viscoelastic moduli and the induction of a TGB A -gel. The stretchable nature of a free-standing film of the BPI-gel that retains its shape over time is another interesting aspect of the present work.
... Recently, NPs such as gold, silica, alumina nanowire, quantum rods, quantum dots (CdSe, PbS, InP/ZnS) etc. have been dispersed to widen the temperature range of BPLCs [27][28][29][30][31][32]. These NPs not only stabilize the BPs, but are rather helpful in tuning and improving the driving voltage, switching voltage, Kerr constant, hysteresis etc. [27][28][29][30][31][32][33][34][35][36][37]. Effect of varying dimensionality and shape of NPs on BPLCs stability was also reported [37]. ...
... These NPs not only stabilize the BPs, but are rather helpful in tuning and improving the driving voltage, switching voltage, Kerr constant, hysteresis etc. [27][28][29][30][31][32][33][34][35][36][37]. Effect of varying dimensionality and shape of NPs on BPLCs stability was also reported [37]. Indeed, a considerable amount of work on BP stabilization and electro-optical properties is reported in NPs-BPLCs systems. ...
... Indeed, a considerable amount of work on BP stabilization and electro-optical properties is reported in NPs-BPLCs systems. However, the effect of size and concentration of NPs, particularly magnetic NPs on BP widening, interaction mechanism and display parameters are rarely studied [32,37]. ...
Blue phase liquid crystal material having a wide blue phase range of 7 °C was prepared in a binary mixture of nematic and chiral nematic liquid crystals with optimization of chiral dopant concentration. Magnetic nanoparticles of size 20 nm, 40 nm in varying concentrations (<0.5 wt %) could successfully stabilize the blue phase temperature range. Interestingly, the BP stability increases approximately 7.8 °C with an increase in nanoparticles concentration up to a critical concentration (0.1 wt %) and then gradually decreases at higher concentrations of nickel nanoparticles. A detailed comparative electro-optical study of pure blue phase liquid crystal and size dependent nickel nanoparticles doped blue phase liquid crystals is accomplished. The transmission of light increases up to 42–45% for nickel nanoparticles doped blue phase liquid crystal samples than pure blue phase liquid crystal with negligible residual birefringence. An increase in isotropic temperature was noticed in 40 nm nickel nanoparticles doped sample. Also an improvement in threshold voltage, induced birefringence, contrast ratio and Kerr constant with doping of nickel nanoparticles was observed. The present study is a synergistic correlation of size and concentration of nickel nanoparticles with blue phase liquid crystals and sufficiently productive for developing nanoparticles doped blue phase liquid crystal optical devices in future.
... Further simulation studies could assist in revealing the energetically favored configurations as a function of size and anchoring. In a recent study, Draude et al. [99] have reported BP stabilization by means of substantially larger graphene oxide sheets, in the range of few µm. Sheets of such a large size are likely to assemble in the boundaries between BP platelet domains. ...
... Upon further cooling, the mixture into the SmA phase, the grain boundaries with screw dislocations disappear, and the nanosheets remain between the smectic layers. Nevertheless, for essentially larger sheets sizes, such as the ones in µm scale used in other studies [99], a preferable assembly along the surfaces of the grain boundaries cannot be excluded. Regarding using other types of NP geometries, a recent study by Sahoo et al. [103] reports the TGB C * phase stabilization by a small concentration of dispersed Au nanorods. ...
Recent advances in experimental studies of nanoparticle-driven stabilization of chiral liquid-crystalline phases are highlighted. The stabilization is achieved via the nanoparticles' assembly in the defect lattices of the soft liquid-crystalline hosts. This is of significant importance for understanding the interactions of nanoparticles with topological defects and for envisioned technological applications. We demonstrate that blue phases are stabilized and twist-grain boundary phases are induced by dispersing surface-functionalized CdSSe quantum dots, spherical Au nanoparticles, as well as MoS2 nanoplatelets and reduced-graphene oxide nanosheets in chiral liquid crystals. Phase diagrams are shown based on calorimetric and optical measurements. Our findings related to the role of the nanoparticle core composition, size, shape, and surface coating on the stabilization effect are presented, followed by an overview of and comparison with other related studies in the literature. Moreover, the key points of the underlying mechanisms are summarized and prospects in the field are briefly discussed.
... BPs that exhibit over a wide range of temperature were obtained by adding a small amount of photo-reactive monomers and in situ polymerization, providing a temperature range of BPs over 50 °C including room temperature [25,26]. Other strategies have also been proposed to extend the temperature range of BPs, by dispersing nanoparticles [27,28], bent-core molecules [6,29], and T-shaped molecules [30], by confining BPs in the microsized walls [31][32][33], and by designing the chemical structure of LC molecules [34]. Second, cubic BPs generally exhibit polycrystalline structures, which are composed of small platelet domains with different crystallographic orientations. ...
Blue phase (BP) liquid crystals, which self-assemble into soft three-dimensional (3D) photonic crystals, have attracted enormous research interest due to their ability to control light and potential photonic applications. BPs have long been known as optically isotropic materials, but recent works have revealed that achieving on-demand 3D orientation of BP crystals is necessary to obtain improved electro-optical performance and tailored optical characteristics. Various approaches have been proposed to precisely manipulate the crystal orientation of BPs on a substrate, through the assistance of external stimuli and directing self-assembly processes. Here, we discuss the various orientation-controlling technologies of BP crystals, with their mechanisms, advantages, drawbacks, and promising applications. This review first focuses on technologies to achieve the uniform crystal plane orientation of BPs on a substrate. Further, we review a strategy to control the azimuthal orientation of BPs along predesigned directions with a uniform crystal plane, allowing the 3D orientation to be uniquely defined on a substrate. The potential applications such as volume holograms are also discussed with their operation principle. This review provides significant advances in 3D photonic crystals and gives a huge potential for intelligent photonic devices with tailored optical characteristics.
... Recently, inorganic perovskite quantum dots (CsPbBr 3 ) reduce the phase transition temperature with widened BP temperature range [40]. A carbon-based NPs (C 60 , CNTs,) could also increase the BP-I, BP-II by a factor of 5 [41]. Varying concentrations of nickel NPs (size -50 nm) were also studied and observed an improvement in the BP temperature range [42]. ...
Blue phases (BPs) in chiral nematic liquid crystals (LC) remained a field of ample research interest due to their exotic optical properties. In the present work, we report the doping effect of dimensionality varying NPs (alumina nanowires [ANWs] and citrate buffer stabilized gold nanoparticles [GNPs]) on the phase transition temperatures and stability of the BP temperature range using polarizing optical microscopy. An increase in the BP thermal stability after the dispersion of NP is observed than an undoped sample. Doping of GNPs and ANWs could expand the BP temperature range of ∼8.0°C and ∼4.5°C respectively at an optimum concentration of dopants. A decrease in BP temperature range is noticed beyond a critical concentration of doped NPs. A platelet type texture, which corresponds to BP-I/BP-II is clearly seen.
... The pattern of red lines that are also shown in the texture are the domain boundaries that can be determined experimentally from the microphotograph. (Credits: left part of (a) is reproduced by permission after ref. [29], the texture is reproduced from ref. [30]. The oilystreaks schematic of (b) is reproduced by permission from ref. [31], while the oily streaks texture, as well as the polygonal texture of (c) are used by permission from Bohdan Senyuk, taken from his website https://www.personal.kent.edu/~bisenyuk/liquidcrystals/textures2.html, last accessed 04.01.2021). ...
An inverse Voronoi tessellation algorithm is developed that can be applied to a large variety of liquid crystalline textures, yielding the seed positions of individual cells. The patterns formed via Voronoi tessellation describe those observed in the texture micrographs very well, with a similarity in excess of 80%, when employing a harsh numerical measure to describe the similarity between experimental and calculated patterns. This is shown for a number of very different liquid crystalline systems, such as nematics on polymer surfaces, chiral materials like frustrated Blue Phases and cholesteric defect structures, discotics, bolaamphiphiles with columnar phases and metallomesogens. Discrepancies between calculated Voronoi patterns and experimental textures are mainly due to inevitable temperature gradients and nucleation fluctuations, which can in principle not be accounted for by the Voronoi algorithm. The methodology can be used for example in materials optimisation, the construction of complex photonic or diffraction devices and even for electronics with molecular wires based on columnar phases.
