Orientation control of two-dimensional (2D) colloidal
liquid crystals
in both microscopic and macroscopic scales holds massive promise for
improved multifield applications. In this respect, graphene oxide
(GO) is used as a platform substance for 2D carbon-based lyotropic
liquid crystal (LC) materials. Here, we design the directed alignment
of aqueous GO-LC dispersion confined in a rectangular capillary tube.
The isotropic GO dispersion is loaded into a horizontal capillary
and subsequently concentrated to the LC phase by slow water evaporation
at open ends of the tube. An obtained surprising result, GO layers
organize normal to the inner surfaces of the capillary with a highly
ordered orientation of the optic axis over tens of millimeters. Such
transverse orientation of GO layers originates from the meniscus region
and then moves toward the center, caused by the interfacial effect
and the sequential isotropic-to-nematic transition. This aligned mesomorphic
system is characterized via optical retardation,
nematic order parameter, absorption, and modified Cauchy’s
transmission equation about the dependency of both birefringence and
wavelength with concentration. Finally, the aligned GO-LC layers are
preserved in a polymer composite matrix by photopolymerizing the evaporation-aligned
GO/acrylamide-LC dispersion confined in a capillary. This composite
shows higher thermal stability than polyacrylamide until 500 °C
of about 6.1%. Our experimental findings provide efficient advantages
for controlling the orientation of GO-LC and 2D materials, beneficial
for diverse optical applications due to their directional ordering.
Air pollution is a severe concern globally as it disturbs the health conditions of living beings and the environment because of the discharge of acetone molecules. Metal oxide semiconductor (MOS) nanomaterials are crucial for developing efficient sensors because of their outstanding chemical and physical properties, empowering the inclusive developments in gas sensor productivity. This review presents the ZnO nanostructure state of the art and notable growth, and their structural, morphological, electronic, optical, and acetone-sensing properties. The key parameters, such as response, gas detection limit, sensitivity, reproducibility, response and recovery time, selectivity, and stability of the acetone sensor, have been discussed. Furthermore, gas-sensing mechanism models based on MOS for acetone sensing are reported and discussed. Finally, future possibilities and challenges for MOS (ZnO)-based gas sensors for acetone detection have also been explored.
Here, we study the dielectric and optical properties of two‐dimensional (2D) WX2 monolayers, where X is Cl, O, S, Se, and Te. First principle electronic band structure calculations reveal that all materials are direct band gap semiconductors except WO2 and WCl2, which are found to be indirect band gap semiconducting 2D materials. The dielectric response of these materials is also systematically investigated. The obtained results suggest that these materials are suitable as dielectric materials to suppress unwanted signal noise. The optical properties of these 2D materials, such as absorption, reflection and extinction coefficients, refractive index, and optical conductivity, are also calculated from the dielectric function. It is found that these materials exhibit excellent optical response. The present electronic, dielectric, and optical findings indicate that WX2 monolayers have an opportunity in electronic, optical, and optoelectronic device applications.
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