Browsing by Author "Ayushi Rastogi"

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Dielectric and electro-optical properties of zinc ferrite nanoparticles dispersed nematic liquid crystal 4’-Heptyl-4-biphenylcarbonnitrile
(Taylor and Francis Ltd., 2020) Fanindra Pati Pandey; Ayushi Rastogi; Rajiv Manohar; Ravindra Dhar; Shri Singh
In this work, comprehensive results on dielectric and electro-optical properties of pristine and zinc ferrite (ZnFe2O4) nanoparticles (NPs) dispersed in host nematic 4ʹ-Heptyl-4-biphenylcarbonnitrile (7CB) systems are reported. The dielectric and EO properties of pristine and NPs dispersed (concentrations 0.05, 0.1, 0.15, 0.2, 0.3 and 0.5 wt%) into the host nematic system have been studied. We have seen uniform NPs dispersion into nematic 7CB up to 0.15 wt% concentration of NPs by the POM. The NPs aggregation starts at 0.2 wt% dispersion. It is shown that the dielectric and electro-optical properties are strongly influenced by the concentration of NPs in host nematic and applied electric field. The dielectric anisotropy is maximum for the NPs dispersed system of 0.15 wt% concentration. The Birefringence, parallel and perpendicular components of permittivity and conductivity are found to be dependent on temperature and concentration of NPs into host matrix. In pure nematic material, small memory is seen but in NPs dispersed systems noticeable memory is found. In particular, pronounced memory is found for the dispersed system of 0.3 wt% concentration of NPs. © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group.
Effect of carbonaceous oil palm leaf quantum dot dispersion in nematic liquid crystal on zeta potential, optical texture and dielectric properties
(Springer Medizin, 2021) Ayushi Rastogi; Fanindra Pati Pandey; Avanish Singh Parmar; Shri Singh; Gurumurthy Hegde; Rajiv Manohar
In the present work, the dispersion of oil palm leaf based carbonaceous quantum dots (OPL QDs) in nematic liquid crystal (NLC) E 48 eutectic mixture has been reported. The dispersed systems with concentrations 0.1, 0.2, and 0.3 wt% are designated respectively, as MIX 1, MIX 2, and MIX 3. The objective of this study is to analyze the results on the zeta potential, optical texture, dielectric constant, dielectric loss, conductivity, dielectric strength, relaxation frequency, specific power loss and total power loss of pure and OPL QDs dispersed nematic E 48 system. Zeta potential measurement has been performed in the solution state to ensure dispersion stability. The optical textures and dielectric results are recorded after filling the respective samples in sample cells. The core findings in the present study show that the zeta potential varies from − 23.43 mV to + 28.07 mV that signifies the stability of OPL QDs suspension in LCs. Specific power loss (SPL) and total power loss (TPL) are found to be least for MIX 1 which shows that the problem of high power consumption in LCDs can be resolved by dispersing a small weight percent concentration of OPL QDs in LC medium (MIX 1). Improved molecular alignment in the dispersed system has been observed from the textural study which finds its application in good contrast display devices. The color change in the aligned textures with temperature has been attributed to the birefringence change. The porous nature of carbonaceous OPL QDs has its application in supercapacitors. The benchmark results of this study highlight the effect of temperature and frequency on dielectric parameters for both planar and homeotropic state of E 48 LCs. OPL QDs dispersed system display increased conductivity for MIX 3. The decrease in the activation energy for OPL QDs dispersed system in comparison to pure LC material E 48 is a consequential result of the potential barrier change. The increment in the dielectric strength and relaxation frequency of OPL QDs dispersed system is noticed in comparison to pure E 48. These outcomes open the door for the applicability of present LCs in the field of both display and non-display devices like sensors, supercapacitors, low power consumption displays, energy conversion, and electrical storage devices as well as advanced smart systems. Graphical abstract: [Figure not available: see fulltext.]. © 2021, Islamic Azad University.
Effect of doping ofcd1−xznxs/zns core/shell quantum dots in negative dielectric anisotropy nematic liquid crystal p-methoxybenzylidene p-decylaniline
(MDPI AG, 2021) Ayushi Rastogi; Fanindra Pandey; Rajiv Manohar; Shri Singh
We report the effect of the doping of Cd1−xZnxS/ZnS core/shell quantum dots (CSQDs) in nematic liquid crystal p-methoxybenzylidenep-decylaniline (MBDA) at 0.05 wt/wt%, 0.1 wt/wt%, 0.15 wt/wt%, 0.2 wt/wt%, 0.25 wt/wt%, and 0.3 wt/wt% concentrations of CSQDs in MBDA. Dielectric parameters with and without bias with respect to frequency have been investigated. The change in electro-optical parameters with temperature has also been demonstrated. The increase in the mean dielectric permittivity was found due to the large dipole moment of CSQDs, which im-pose stronger interactions with the liquid crystal molecules. The dielectric anisotropy changes sign on doping CSQDs in MBDA liquid crystal. It was concluded that the CSQD doping noticeably increased the dielectric permittivity of nematic MBDA in the presence of an electric field. The doping of CSQDs in nematic MBDA liquid crystal reduced the ion screening effect effectively. This phe-nomenon is attributed to the competition between the generated ionic impurities during the as-sembling process and the ion trapping effect of the CSQDs. The rotational viscosity of nematic liquid crystal decreased with increasing concentration of the CSQDs, with a faster response time observed for the 0.05 wt/wt% concentration. The birefringence of the doped system increased with the inclusion of CSQDs in MBDA. These results find application in the field of display devices, phase shifters, LC – gratings, TIR waveguide, industries, and projectors. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
Enhancing physical characteristics of thermotropic nematic liquid crystals by dispersing in various nanoparticles and their potential applications
(Institute for Ionics, 2023) Ayushi Rastogi; Archana Mishra; Fanindra Pati Pandey; Rajiv Manohar; Avanish Singh Parmar
Herein, we have summarized the doping of thermotropic nematic liquid crystals (LCs) with different nanoparticles (NPs) and its consequences on dielectric, optical, and electro-optical properties. The challenging task is to improve the physical properties of nematic LCs for its applications in nanotechnology, which include sophisticated and highly advanced modern displays, tunable lenses, sensors, etc. The negative effects that affect the overall performance of LCs devices are image sticking problem, image flickering, and slow response time which is mainly affected by ions and alignments. The trapping of charged ionic impurities and suppression of screening effect through NPs in LC medium produces strong electric field and van der Waal forces linked with the LC molecules and the alignment layers. The electric field controls the orientation of LC molecules and thus transforms its physical behavior. In this article, we have summarized and discussed the physical properties of thermotropic nematic LCs with the dispersion of NPs. These thermotropic LCs require improvement in their properties for the better functioning of LC products. A decade of enthusiastic research has designed the lane to the suspension of NPs in LC matrix for resolving the issues on nanotechnology. NPs (guest) that are embedded in LCs (hosts) influence its material parameters. The present article focuses on the review of published articles which report various types of NPs (metal oxide NPs, carbon-based NPs, semiconducting NPs, ferroelectric (FE) such as BaTiO3, magnetic NPs, and metallic NPs) as dopants and its sound realization on the physical properties of thermotropic nematic LCs. The topological defects and the effect of dispersion of colloidal particles in nematic LCs have been discussed. The decrease in the anchoring energy with decreasing radius of particles has been revealed. This review considers the significant role of NP self-assembly in LC medium which depends on its shape, size, and surface chemistry that affect the orientation order of LC molecules. From the application point of view, this review provides the literature support where the mixing of LCs and NPs solves the technological problems. The explanation on the improvement in the performance/material parameters is well supported by the experimental literature study reported in this review. © 2022, Qatar University and Springer Nature Switzerland AG.
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
Investigation of dielectric and optical properties of pure and diamond nanoparticles dispersed nematic liquid-crystal PCH5
(Taylor and Francis Ltd., 2021) Dhananjay Kumar Gaur; Ayushi Rastogi; Harshita Trivedi; Avanish Singh Parmar; Rajiv Manohar; Shri Singh
In the present work, we have dispersed diamond nanoparticles (DNPs) in nematic liquid crystal 4-(Trans-4ʹ-n-Pentylcyclohexyl) Benzonitrile (PCH5) and studied the dielectric and optical properties of pure and DNPs dispersed nematic systems. We have investigated the effect of dispersion of DNPs (concentrations 0.5 and 1.0 wt%) in nematic liquid crystals (NLC) PCH5 on the dielectric permittivity, dielectric loss, dielectric anisotropy, photoluminescence, UV-Vis absorbance. It has been found that these properties are influenced by the dispersion of DNPs in nematic PCH5 system and applied electric field. Due to the dispersion of DNPs (1.0 wt% concentration) in PCH5, a significant decrease in the relative permittivity occurs. The relaxation peaks of dielectric loss shifts towards higher frequency side for NLC-DNPs composites. The dielectric anisotropy has been found to decrease with the dispersion of DNPs into pure NLC. The PL emission and UV-Vis absorbance for the dispersed systems have been decreased. An effort has been made to explain the observed results on the basis of interaction between nematic molecules and diamond NPs. The possible applications have also been suggested for the dispersed systems in this study. © 2020 Informa UK Limited, trading as Taylor & Francis Group.
Investigation of dielectric, optical and zeta potential properties of pure and zinc ferrite nanoparticles dispersed nematic liquid crystal PCH5
(Springer Science and Business Media Deutschland GmbH, 2022) Dhananjay Kumar Gaur; Fanindra Pati Pandey; Ayushi Rastogi; Avanish Singh Parmar; Rajiv Manohar; Shri Singh
The present work reports the results on dielectric and optical properties, and zeta potential of pure and zinc ferrite magnetic nanoparticles (ZnFe2O4 NPs) dispersed nematic liquid crystals (NLC) 4-(trans-4'-n-pentylcyclohexyl) benzonitrile (PCH5). The ZnFe2O4 NPs of three different concentration 0.25, 0.5 and 1.0 wt% have been dispersed in host nematic. The effect of ZnFe2O4 NP dispersion in NLC PCH5 on dielectric permittivity, dielectric anisotropy, ac conductivity, photoluminescence, Raman spectra and zeta potential has been studied. It has been observed that these properties are influenced by the concentrations of NPs in host nematic and applied electric field. Significant decrease in dielectric permittivity and dielectric anisotropy due to the presence of NPs in host nematic matrix has been observed. For the NP concentrations of 0.25 and 0.5 wt% in PCH5, photoluminescence intensity is increased, but it is decreased for the 1.0 wt% concentration of NPs in host nematic matrix. The numerical values of zeta potential are decreased with the concentrations of NPs. This result provides useful information on the stability and aggregation dynamics of the dispersed systems. In the profile of Raman spectra, variation in intensities is found for different orientations. An effort has been made to explain the observed results on the basis of interaction between NPs and nematic molecules. © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.
Optical properties and zeta potential of carbon quantum dots (CQDs) dispersed nematic liquid crystal 4′- heptyl-4-biphenylcarbonitrile (7CB)
(Elsevier B.V., 2020) Fanindra Pati Pandey; Ayushi Rastogi; Shri Singh
In this work, carbon quantum dots (CQDS) of three concentrations 0.1, 0.2 and 0.5 wt% have been dispersed in nematic liquid crystal 4′-Heptyl-4-biphenylcarbonitrile (7 CB). The results on the optical properties and zeta potential of pure and CQDs dispersed nematic 7CB have been reported. It has been observed that the dispersion of CQDs in host nematic matrix induces quenching of photoluminescence and reduces the Ultra-Violet-Visible (UV–Vis) absorbance of pure nematic at a lower wavelength. From the result of fluorescence decay profile, the fluorescence life time of pristine and dispersed nematic systems have been obtained. No remarkable changes in nematic lifetime in the presence of CQDs have been observed, which confirm that no energy is transferred from nematic to CQDs. Further, it has been found that due to dispersion of CQDs the numerical values of zeta potential are increased for the dispersed systems with 0.1 and 0.2 wt% concentrations of CQDs as compared to pure 7 CB. This result demonstrates that the study of zeta potential provides useful information on the stability and aggregation of the CQDs dispersed nematic systems. © 2020 Elsevier B.V.
Performance benchmarking of different convolutional neural network architectures on COVID-19 dataset
(Bentham Science Publishers, 2024) Harsh Kumar Mishra; Anand Singh; Ayushi Rastogi
The utilization of chest X-rays could offer valuable assistance in the initial screening of patients before undergoing RT-PCR testing. This potential approach holds promise within hospital environments grappling with the challenge of categorizing patients for either general ward placement or isolation within designated COVID-19 zones. This study investigates the use of chest X-rays as a preliminary screening technique for suspected COVID-19 cases in hospital settings, given the limited testing capacity and probable delays for RT-PCR testing. We assess how well several neural network architectures perform in automated COVID-19 identification in X-rays with the goal of locating a model that has the highest levels of sensitivity, low latency, and accuracy. The results reveal that InceptionV3 exhibits better robustness while MobileNet obtains the maximum accuracy. This strategy may help healthcare organisations better manage patients and allocate resources optimally, especially when radiologists are hard to come by. This will help in choosing an architecture that has better accuracy, sensitivity, and lower latency. The chosen models are pre-trained using the technique of transfer learning to save computation power and time. After the training and testing of the model, we observed that while MobileNet gave the best accuracy among all the models (VGG16, VGG19, MobileNet and InceptionV3), IncpetionV3 was still better when it comes to robustness. © 2024, Bentham Books imprint. All rights reserved.
Thermodynamic model to study the structural and electro-optical properties of chiral antiferroelectric smectic C phase exhibited by mesogenic homologous series 3FnHBM6(s) and W-316 mixture
(Taylor and Francis Ltd., 2023) Abhilasha Singh; Ayushi Rastogi; Shri Singh
Using a thermodynamic model developed by us to study the structural and electro-optical properties of (Formula presented.) phase, we investigate the temperature dependence of helical pitch, tilt angle and spontaneous polarization of a homologous series of fluorinated biphenyl benzoate esters (3FnHBM6, n = 2, 5, 7) and one of the series W-316-3 obtained from the mixture of two chiral liquid crystalline compounds 6F2OBi and 3F6HBM6. The free-energy density of the system exhibiting (Formula presented.) phase is written as an expansion series in terms of all the relevant degrees of freedom: (Formula presented.), ψ, P, q and the resulting coupling terms between these order parameters. The values of Landau coefficients are determined from the experimental data of antiferroelectric mesogens 3FnHBM6 (n = 2, 5, 7) and W-316-3 in the (Formula presented.) phase. Using these coefficients, the electro-optical and structural properties have been studied. We have found good agreements between the theoretical and experimental results. © 2023 Informa UK Limited, trading as Taylor & Francis Group.
Time-resolved fluorescence and UV absorbance study on Elaeis guineensis/oil palm leaf based carbon nanoparticles doped in nematic liquid crystals
(Elsevier B.V., 2020) Ayushi Rastogi; Fanindra Pati Pandey; Gurumurthy Hegde; Rajiv Manohar
Time resolved fluorescence measurement and UV absorbance study on oil palm leaf based nanoparticles (OPL) doped with nematic liquid crystal E 48 in 0.1, 0.2 and 0.3 wt/wt% concentration abbreviated as mixture 1 (MIX 1), mixture 2 (MIX 2) and mixture 3 (MIX 3) were conducted. OPL biomolecule loaded graphene oxide –nematic E 48 liquid crystal system has been fabricated for biosensor application. The interaction of OPL nanoparticles with E 48 nematic liquid crystal having different concentration of nanoparticles has been explored. Pure nematic E 48 and its doped system have been examined by time- resolved fluorescence spectroscopy (TRFS) technique. Variation in the nanoparticles concentration strappingly affects the fluorescence emissions. Lack of Förster resonance energy transfer (FRET) was found in all composites. This manuscript unveils the purpose of a range of factors, such as dipolar interface between donor and acceptor molecules, nanoparticles orientation and its proximity distance that may be accountable for the non-appearance of FRET. Nematic nanoparticles doped system forms an antique composition of luminescent material even though the fluorescence characteristics of host are customized in the existence of nanoparticles by the molecular alignment modification. Variation in lifetimes of nematic nanoparticles doped system has been observed. These results find its applicability in photonic displays, photovoltaic devices, biosensors etc. © 2020