Browsing by Author "Chandran, A."

Now showing 1 - 5 of 5

Effect of nickel oxide nanoparticles on dielectric and optical properties of nematic liquid crystal
(American Institute of Physics Inc., 2015) Jamwal, G.; Prakash, J.; Chandran, A.; Gangwar, J.; Srivastava, A.K.; Biradar, A.M.
In the present paper, we have studied the improvement in dielectric and optical properties of nematic liquid crystal (NLC) by doping of nickel oxide (NiO) nanoparticles. We have observed the dielectric and optical properties of pure and doped cells in order to understand the influence of NiO nanoparticles in the pure NLC. The experimental results have been analyzed through dielectric spectroscopic and optical texural methods.Detailed studies of dielectric parameters such as dielectric permittivity, dielectric loss and dielectric loss factor as a function of frequency with temperature were carried out. It has been observed that on doping the nanoparticles in NLC, the value of dielectric parameters (dielectric permittivity, dielectric loss and dielectric loss factor) decreases. The impedance and resistance of both pure and nanoparticles doped NLC cells were studied and found that for doped NLC, these parameter have low value. In addition to this, optical textures of the pure and doped samples have also been observed with a polarizing optical microscope at room temperature. All the results i.e. related to the investigation of dielectric and electro-optic properties have been explained by using existing theory of NLC. ? 2015 AIP Publishing LLC.
Preparation and characterization of MgO nanoparticles/ferroelectric liquid crystal composites for faster display devices with improved contrast
(2014) Chandran, Achu; Prakash, Jai; Naik, Kush Kumar; Srivastava, Avanish; Dabrowski, Roma; Czerwinki, Michat; Biradar, A. M.; Chandran, A.; Prakash, J.; Naik, K.K.; Srivastava, A.K.; Da?browski, R.; Czerwi?ski, M.; Biradar, A.M.
In this article, we present the formulation and characterization of a ferroelectric liquid crystal (FLC) mixture W301 composed of pyrimidine compounds. We observed that upon doping magnesium oxide nanoparticles (MgO NPs) into the host FLC, the MgO NPs/FLC composite showed significantly faster response and improved optical tilt angle. The decreased response time in the MgO NPs/FLC composite has been attributed to the decrease in rotational viscosity and increase in surface anchoring energy. The decrease in rotational viscosity of the composite is due to the torque experienced by both MgO NPs and FLC in the presence of an electric field and perturbations of order parameters of FLC. Due to the enhanced surface interaction of MgO NPs having surface defects with mesogens, strong surface anchoring is experienced on the FLC molecules that not only increased the speed of the response but also improved the optical tilt angle of the MgO NPs/FLC composites, which ultimately resulted in improved contrast. A systematic approach has been followed to elucidate the idea of designing faster display devices with improved contrast based on MgO NPs/FLC composites. ? 2014 The Royal Society of Chemistry.
Role of cell thickness in tailoring the dielectric and electro-optical parameters of ferroelectric liquid crystals
(Taylor and Francis Ltd., 2015) Prakash, J.; Chandran, A.; Malik, A.; Biradar, A.M.
Here, we report thickness dependence of dielectric and electro-optical parameters in ferroelectric liquid crystals (FLCs) without surface stabilisation. The dependence of dielectric and electro-optical parameters on cell thickness is observed by dielectric spectroscopy and electro-optical measurements. The dielectric permittivity (Formula presented.) measured by varying the cell thickness showed increase of (Formula presented.) with increase of cell thickness which is attributed to the presence of more ions and larger contributions of Goldstone mode in thick cells. The spontaneous polarisation also shows increment with increase of cell gap up to certain thickness range. The rotational viscosity decreases with increase in the cell thickness whereas the response time is more for thicker cells. The decrease in the rotational viscosity is attributed to lowering of elastic deformation with increase in cell thickness and the response time is directly proportional to cell gap. These studies would be utilised to understand the effect of cell thickness on dielectric and electro-optical properties of FLC materials and optimising the material parameters with cell thickness for better and efficient liquid-crystal-based devices. ? 2015 Taylor & Francis.
Self assembled monolayer based liquid crystal biosensor for free cholesterol detection
(American Institute of Physics Inc., 2014) Tyagi, M.; Chandran, A.; Joshi, T.; Prakash, J.; Agrawal, V.V.; Biradar, A.M.
A unique cholesterol oxidase (ChOx) liquid crystal (LC) biosensor, based on the disruption of orientation in LCs, is developed for cholesterol detection. A self-assembled monolayer (SAM) of Dimethyloctadecyl[3-(trimethoxysilyl)propyl] ammonium chloride (DMOAP) and (3-Aminopropyl)trimethoxy-silane (APTMS) is prepared on a glass plate by adsorption. The enzyme (ChOx) is immobilized on SAM surface for 12 h before utilizing the film for biosensing purpose. LC based biosensing study is conducted on SAM/ChOx/LC (5CB) cells for cholesterol concentrations ranging from 10mg/dl to 250 mg/dl. The sensing mechanism has been verified through polarizing optical microscopy, scanning electron microscopy, and spectrometric techniques. ? 2014 AIP Publishing LLC.
Zirconia nanoparticles/ferroelectric liquid crystal composites for ionic impurity-free memory applications
(2013) Chandran, A.; Prakash, J.; Ganguly, P.; Biradar, A.M.
We observed an ionic impurity-free memory effect using a zirconia nanoparticles (ZNPs)/ferroelectric liquid crystal (FLC) composite. The pure and ZNPs doped FLC cells have been analyzed by means of dielectric spectroscopy, polarizing optical microscopy and electrical resistance/conductivity measurements. The memory behavior in ZNPs/FLC composite was confirmed by dielectric dispersion, electrical, and optical studies, whereas dielectric loss spectra confirmed the disappearance of the low-frequency relaxation peak, which appears due to the presence of ionic impurities in FLC materials. The observed memory effect has been attributed to minimization of the depolarization field and ionic charges, whereas the reduction of ionic effects has been attributed to the strong adsorption of ionic impurities on the surface of ZNPs. The ZNPs dispersed in FLCs may play a role in trapping the impurity ions (minimize the depolarization fields) under applied voltage and cause a better memory effect in ZNPs doped FLC material. Moreover, the ion adsorption capability of ZNPs is found to be almost independent of temperature as the value of resistance did not change remarkably on increasing the temperature. The reduction of ionic impurities of FLCs by doping ZNPs did not show degradation over time, as we repeated the experiments on the same sample cells after many days and did not find ionic effects in the ZNPs doped FLC materials. These studies would be helpful to provide an idea for designing ionic impurity-free memory devices. ? 2013 The Royal Society of Chemistry.