Topological defects (TDs) appear in all branches of physics due to the simplicity of generic mechanisms: The necessary condition for their existence is spontaneous symmetry breaking in a relevant ...physical field. Nematic liquid crystals (NLCs) represent an ideal testbed for their study and they can display point, line, textures, and in favorable conditions also wall defects. TDs in NLCs can be relatively easily created, controlled, and experimentally observed. This enables a detailed and controlled analysis of their physical properties, leading to the cross‐fertilization of knowledge among different areas of physics, including condensed matter, particle physics, and cosmology. Furthermore, TDs in NLCs could be exploited in diverse applications. Herein, some salient features of most common TDs in NLCs, their generic mechanisms, their importance for fundamental science, and possible applications based on them are illustrated.
Topological defects (TDs) appear in all branches of physics due to the simplicity of generic mechanisms. Nematic liquid crystals (NLCs) represent an ideal testbed for their study. In them, TDs can be relatively easily created, controlled, and observed, which enables a detailed and controlled analysis of their physical properties. Furthermore, TDs in NLCs can be exploited in diverse applications.
Topological defects (TDs) are a consequence of symmetry breaking phase transitions and are ubiquitous in nature. An ideal testbed for their study are liquid crystals (LCs) owing to their large ...response to external stimuli and their large electrical and optical anisotropies. In this paper, we perform numerical simulations of topological defects of
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enforced by the confining boundary. We use the Landau–de Gennes phenomenological model in terms of the tensor nematic order parameter and the Jones beam propagation model to simulate polarized optical microscopy images. We demonstrate the structure of closed disclination loops near the boundary known as boojums that can be topologically charged or chargeless. We show that pairs of chargeless disclination loops can interact repulsively or attractively depending on if they are arranged parallel or antiparallel, respectively. Sufficiently closely spaced antiparallel pairs can rewire while parallel pairs simply exhibit stronger bending due to the repulsion.
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Two dimensional (2D) graphene and its derivatives modification with nanomaterials for formation of hybrid/nanocomposites undergo stimulus-induced optical and electrical changes which are important ...for many new switchable device technologies. The feature article deals with a straight forward and versatile technique for the fabrication of semiconductor nanomaterials (CdS and TiO
2
) nanomaterials dispersed liquid crystals (NDLC) or graphene dispersed liquid crystal (GDLC) by stretching hydrogen bonds (H-) in the precursor droplets between two substrates to form a liquid bridge. Fewer liquid crystals (LCs) possess a conventional oriented nematic phase with optimal performances. Evolving advantages of thin-film nanocomposite materials and switchable devices have fueled several developments in the field of flexible electronics, high contrast ratio smart display and opto-electronics. These advantages have been complemented with the expansion of novel composite materials such as GDLC and NDLC as sensors to monitor the inflammability, explosive nature and toxicity of chemicals. This discussion also delves into the fabrication of graphene assembly polymer nanocomposites dispersed in LCs, the necessity for bio-polymer incorporation and their bio-sensing and antimicrobial applications. Additionally, discussed the issues and challenges associated with understanding and exploiting the potentials of smart switchable devices fabricated by nanomaterials or polymer/graphene hybrid composite matrix. Following substantial development and optimized over decades, a novel mechanism employed in smart switchable devices via GDLC hybrid nanocomposite matrix has been found to offer numerous benefits including being cost-effective, possessing a large area compatibility and large scalability in addition to seamless heterogeneous integration.
Topological Defects
The curvature of a closed manifold exhibiting orientational order has a strong impact on positions and the number of topological defects (TDs). The surface integrated Gaussian ...curvature determines the total winding number of TDs within the manifold. If a region possessing a large enough negative Gaussian curvature is introduced it can trigger pairs {defect, antidefect}, possessing opposite signs of the winding number. More details can be found in article number 2000752 by Mitja Kralj, Marko Kralj, and Samo Kralj.
Smart electronic materials 'nanographene' stated, its significant authentication has undergone massive improvements and has emerged as a 'material of the century' in materialize fields of 'Chemical ...Biology' and 'Materials Chemistry'. 'Graphene' as a wonder material has been proposed to possess a high surface area (∼2600 m
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), high portability of charge carriers and excellent mechanical qualities. Moreover, the long-extend π-conjugation of graphene is an essential photocatalytic property enabling wide ranging biosensor activities. Herein, critical review article reflects well known yet a brand-new novel material 'nanographene' and its versatile integrations, utilized for substantial enrichment of desired properties. Target cost-effectiveness, plasticity, and environment-friendliness of melt mixing/compounding fabrication strategy employed to utilize in-vivo, in-vitro, and in- situ, pharmaceutical, nano-imaging protocols. Owing to nanographene's wide range expansion, summarized latest breakthroughs in Materials Science as well as Biomedical utilizations including cancer nanotechnology, drug delivery, tissue manufacturing, scaffold, photo-thermal therapy, antimicrobial activities, made up of exploring the significant opportunities and key challenges in this novel emerging field.
We study numerically curvature and electric field driven domain formation and reorientations in two-dimensional nematic liquid crystals within square confinement. We use the Landau-de Gennes ...description in terms of the nematic tensor order parameter. We show that on increasing the amplitude of a sinusoidally shaped confining wall, pairs {defect, antidefect} are formed, which enable insertion of domains displaying significantly different average orientational order with respect to the surrounding nematic body. Furthermore, we study E-driven transformation between two competing degenerate domain-type structures. We show that transformations could be mediated via qualitatively different intermediate structures possessing topological defects.
It is well known that positions of topological defects (TDs) in liquid crystals can be manipulated experimentally by locally distorting the liquid crystalline (LC) order, as for example by melting ...induced by optical tweezers. In this work, we study numerically the nematic ordering profiles and the corresponding topological defect configurations in thin nematic liquid crystalline shells controlled by imposed local distortion of LC order. We demonstrate that within curved LC films such manipulations could be strongly affected by local Gaussian curvature if it exhibits strong spatial variations. We use mesoscopic approach in which the shell geometry and LC orientational order are described by curvature of the surface and nematic order parameter tensor. For illustration purposes, we consider LC shells exhibiting spherical topology. We show that on increasing prolateness of shells, which imposes spatially inhomogeneous Gaussian curvature, TDs are relatively strongly “glued” to a local Gaussian curvature.
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Plasmonic nanomaterials (PNMs) and catalytically active surfaces, when combined, provide novel opportunities for a wide range of potential applications of catalysis. When stimulated by the right kind ...of light, surface plasmons can be put to use to either directly cause or indirectly facilitate a wide variety of chemical reactions. PNMs are currently the center of extensive research that is being conducted for the purpose of determining whether or not they could be utilized to improve the efficiency of catalytic reactions. This is due to the fact that PNMs have the alluring ability to interact with light in a powerful fashion. These structures exhibit the singular property of localised surface plasmon resonance, which transforms light of a particular wavelength ranges into hot charge carriers, together with high local electromagnetic fields, or heat, which may all contribute in different ways to increasing the reaction efficiency. Plasmon-mediated catalysts, which go beyond the highly influential application of supported gold nanomaterials (NMs) to photo-oxidation reactions, can be utilised to create a greater variety of visible-light induced catalysts by combining various metals and supports with available Au, Ag, and Cu NMs and PNMs photocatalysts. Plasmon-mediated catalysts go beyond the highly influential application of supported gold nanomaterials (NMs) to photo-oxidation reactions. This would make it possible to develop a greater diversity of photocatalysts, which are catalysts that can be powered by visible light. This review will focus on the PNMs-based catalyst for alcohol oxidation, which will be addressed within the framework of this research.
The impact of the intrinsic curvature of in-plane orientationally ordered curved flexible nematic molecules attached to closed 3D flexible shells was studied numerically. A Helfrich-Landau-de ...Gennes-type mesoscopic approach was adopted where the flexible shell's curvature field and in-plane nematic field are coupled and concomitantly determined in the process of free energy minimisation. We demonstrate that this coupling has the potential to generate a rich diversity of qualitatively new shapes of closed 3D nematic shells and the corresponding specific in-plane orientational ordering textures, which strongly depend on the shell's volume-to-surface area ratio, so far not predicted in mesoscopic-type numerical studies of 3D shapes of closed flexible nematic shells.
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