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Dispersion of fluorescent dye in the nematic liquid crystal : enhanced photoluminescence and high birefringence

Pathak G., Agrahari K., Roy A., Srivastava A., Strzezysz O., Garbat K., Manohar R.

Opto-Electronics Review

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2018

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Vol. 26, No. 4

317--324

EN

In the present investigation optical, electro-optical and dielectric properties have been measured for nematic liquid crystal (NLC) material 1550C which is consisted of 4’-(trans, trans-4-alkylbicyclohexyl) carbonates and 4’-(4-(trans,trans-4-alkyl)-4-cyanobicyclohexane, dispersed with fluorescent dye (Benzo 2,1,3 Thiadiazole) in two different concentrations. Photoluminescence has been enhanced for dye dispersed system which is the key finding of this investigation. UV absorbance study has also been performed and found to be increased for composite system. Enhanced birefringence after dispersion of dye into pure NLC is also a prominent result of this investigation. Relative permittivity, threshold voltage and dielectric anisotropy have also been measured and found to be increased. The outcome of the present work may be very useful in the construction of liquid crystal displays (LCDs).

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Analysis of birefringence property of three different nematic liquid crystals dispersed with TiO₂ nanoparticles

Pathak G., Katiyar R., Agrahari K., Srivastava A., Dabrowski R., Garbat K., Manohar R.

Opto-Electronics Review

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2018

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Vol. 26, No. 1

11--18

EN

In the present work TiO₂ nanoparticles (NPs) have been dispersed into three different nematic liquid crystals (2020, 1823A and 1550C) in different concentration. The value of the birefringence (Δn) has been calculated by the transmitted intensity method at a 632.8 nm wavelength. NLC 2020 used in the present study is a high birefringent material (Δn = 0.44), NLC 1550C is a low birefringent material (Δn = 0.067) and NLC 1823A is a mid birefringent material (Δn = 0.14). An increased value of birefringence has been found after dispersion of TiO₂ NPs in all three NLCs but this increment depends upon the concentration of the dopant material, temperature range and chemical character of the mixtures. It is suggested that this LC materials can be applicable in making of phase shifters, compensators and many more photonic devices.

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Effect of radiation on unsteady free convection flow bounded by an oscillating plate with variable wall temperature

Pathak G., Maheshwari C., Gupta S. P.

International Journal of Applied Mechanics and Engineering

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2006

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Vol. 11, no 2

371-382

EN

The object of the paper is to study the radiation effects on an unsteady free convective flow through a porous medium bounded by an oscillating plate with a variable wall temperature. The momentum and energy boundary layer equations have been solved by taking series expansions of velocity and temperature function in powers of product of magnetic field and time. The analytical solution of resulting ordinary differential equations has been obtained in terms of repeated integrals of complementary error functions. Also, the velocity and temperature profiles, for different values of the parameters, have been drawn and discussed.