Browsing by Author "Abhishek Kumar Misra"

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Dielectric and electro-optical properties of polymer-stabilized liquid crystal system
(Springer Verlag, 2016) Mukti Pande; Pankaj Kumar Tripathi; Abhishek Kumar Misra; Shashwati Manohar; Rajiv Manohar; Shri Singh
In this work, we report the results of dielectric and electro-optical properties as a function of temperature for both pure liquid crystal matrix and polymer-stabilized liquid crystal (PSLC). The threshold and saturation voltages have been determined from transmission–voltage curves. We have studied the polymer domains formation in PSLC with variation of concentration of polymer in liquid crystal matrix. It is observed that the dielectric anisotropy of PSLC is significantly influenced by the polar order present in the polymer domains environment. A delicate interplay between the orientational order of liquid crystal and polymeric domains determines the molecular orientations of PSLC with respect to the director of the LC system. © 2016, Springer-Verlag Berlin Heidelberg.
Effect of UV light irradiation on the dielectric behaviour of liquid crystal/nano composite
(Taylor and Francis Inc., 2017) Kamal Kumar Pandey; Alok Chandra Dixit; M. Saleem khan; Pankaj Kumar Tripathi; Abhishek Kumar Misra; Rajiv Manohar
In this work, we investigate the effect of UV light irradiation on the dielectric parameters of the nematic liquid crystal (5CB) containing dispersed ZnO nanoparticles. With addition of nanoparticles, nematic LC's are promising new materials for a variety of applications in energy harvesting, displays and photonics including the liquid crystal laser. To realize many applications, however one must optimize the properties of liquid crystal and understand how UV light irradiation interacts with the nanoparticles and LC molecules in dispersed/doped LC. The dielectric permittivity and loss factor are discussed for the pure nematic LC and dispersed/doped system after, during and before UV light exposure. Dielectric relaxation spectroscopy was carried out in the frequency range 100 Hz-10 MHz in the nematic mesophase. © 2017 Taylor & Francis Group, LLC.
Electro-optic switching and memory effect in suspension of ferroelectric liquid crystal and iron oxide nanoparticles
(Institute of Physics Publishing, 2019) Abhishek Kumar Misra; Pankaj Kumar Tripathi; Kamal Kumar Pandey; Fanindra Pati Pandey; Shri Singh; Abhilasha Singh
In this work, impact of dispersion of iron oxide nanoparticles (Fe2O3 NPs) into ferroelectric liquid crystal (FLC) SCE-13 mixture on the electro-optical and dielectric properties has been studied. It has been found that the dispersion of Fe2O3 NPs in host FLC matrix exhibits pronounced influence on response time, spontaneous polarization, rotational viscosity and voltage required for switching the FLC molecules. Also dispersed system shows memory effect as confirmed by the optical texture and dielectric permittivity studies. Effort has been made to explain the experimental results as for as possible. © 2019 IOP Publishing Ltd.
Estimation of spectroscopic parameters and TL glow curve analysis of Eu3+-activated CaY2O4 phosphor
(Royal Society of Chemistry, 2023) Tirath Ram; Neeraj Verma; Jagjeet Kaur; Abhishek Kumar Misra; Vikas Dubey; Neha Dubey; Marta Michalska-Domańska; Janita Saji; Ram Sagar Yadav
The solid-state reaction method was utilised to create a down-conversion phosphor in an air environment in CaY2O4:Eu3+ nanocrystalline material. The calcination temperature was set at 1000 °C, and the sintering temperature was set at 1300 °C. Following annealing, confirmation of the crystallinity quality of the phosphor was accomplished by the use of X-ray diffraction analysis. The particle size was predicted to be 43.113 nm using Scherrer's formula. To produce down-conversion luminescence spectra, an excitation wavelength of 247 nm was applied with a fluorescence spectrophotometer. The PL got increasingly intense as the concentration of the dopant increased. The maximum intensity was measured at 2.0 mol% of Eu3+ ion, which gradually decreased as the concentration increased because of concentration quenching. To analyse spectrophotometric peak determinations, the approach developed by the Commission Internationale de l'Éclairage (CIE) was used. Thermoluminescence (TL) glow curve analysis of the CaY2O4:Eu3+-doped phosphor manufactured here revealed a wide TL centred at 225 °C, which comprised of so many peaks that may be extracted by the computerised glow curve deconvolution (CGCD) approach using glow-fit software. The associated kinetic parameters were then determined. The prepared phosphor may be useful for application in various display devices upon excitation by 247 nm; the prominent 613 nm peak of the Eu3+ ion (5D0 → 7F2) electric dipole transition features a red component. CaY2O4:Eu3+ phosphors show promise as materials for potential use in phosphor-converted white LEDs in the field of solid-state lighting technology. The linear connection that the TL glow curve has with UV dose provides evidence for its possible use in dosimetry. © 2023 The Royal Society of Chemistry.
Exploring the photoluminescence behavior of antiferroelectric liquid crystals through graphene oxide dispersion
(Elsevier B.V., 2025) Shishir Shukla; Pankaj Kumar Tripathi; Ayushi Rastogi; Ehsan Shakerzadeh; Vijay Singh; V. K. Mishra; Thakur Prasad Yadav; Mithlesh Tiwari; Abhishek Kumar Misra
The photoluminescence properties of antiferroelectric liquid crystal (AFLC) dispersed with graphene oxide (GO) were studied. AFLC-based composites were prepared by dispersing various weight concentrations (0.1 % and 0.3 % wt./wt.) of GO into AFLC. UV absorbance studies were performed using spectrum, time scan, and overlay modes. The decrease in UV absorbance was observed in all of these modes. Red shifts in absorbance bands were observed for both pure AFLC sample and GO/AFLC composite. The UV absorbance maxima for AFLC dispersed with GO shifted from 317.27 nm to 324.57 nm. This shift was attributed to the varying concentrations of GO in the AFLC medium. A significant improvement in the luminescence intensity of AFLC dispersed with GO nanoparticles mixtures was observed. The luminescence intensity increased from 0.3 (pure AFLC) to 1.0 (0.3 % wt./wt.). Furthermore, the luminescence intensity of the AFLC mixture was observed to increase with the concentration of GO for the fixed weight of the AFLC sample. © 2025 Korean Physical Society
Fluorescent dye doped ferroelectric liquid crystal: An anchoring energy, electro-optical and fluorescence study
(Elsevier B.V., 2016) Abhishek Kumar Misra; Pankaj Kumar Tripathi; Rajiv Manohar
In this study anchoring energy parameters, electro-optical (E-O) study along with UV absorption and fluorescence study have been performed for pure ferroelectric liquid crystal (FLC) and three different concentrations i.e. 1%, 3% and 5% of fluorescent dye in pure FLC. The UV absorption has been shifted towards lower frequency side for fluorescent dye doped system in comparison to the pure FLC. Excitation wavelength, emission wavelength and quantum yield have been determined for all the mixtures from fluorescence study. Anchoring energy parameters, spontaneous polarization and response time have been determined by E-O study. The values of these parameters are strongly changed by the concentration of fluorescent dye. © 2015 Elsevier B.V.