Jai Prakash

• Ph. D. (IIT Delhi)
• Professor (Assistant) at Aligarh Muslim University

We present the concentration and temperature dependent optical textures, and dielectric properties of bismuth titanate (Bi 2 Ti 2 O 7 /Bi 4 Ti 3 O 12) (BT2/BT4) nanocomposite doped 4 0-octyl-4-biphenylcarbonitrile (8CB) liquid crystal (LC) mixtures using polarizing optical microscope and dielectric spectroscopic techniques. The optical textures of...

We demonstrate here the impact of doping of CsPbBr3 perovskite quantum dots (CsPbBr3 PQDs, diameter ∼ 7–9 nm) on the molecular alignment, dielectric and memory effect of nematic (N) and smectic A (SmA) phases of a thermotropic liquid crystal material, namely 4-octyl-4′-cyanobiphenyl (8CB) using polarising optical microscope and dielectric spectrosc...

The synthesis of vanadium-doped titanium oxide nanoparticles (VTO NPs) using the co-precipitation method has been reported in the present work. The newly synthesized VTO NPs (~ 93 nm) were characterized using XRD, FTIR, UV–Vis, FESEM, and EDX techniques. Further, these NPs were doped in 4’-octyl-4-biphenylcarbonitrile (commonly known as 8CB) liquid...

Dispersion of quantum dots (QDs) in liquid crystal (LC) medium can effectively modify their dielectric and electro-optical properties which can be useful in LC based display as well as non-display applications. Here, we reported the effect of doping of perovskite quantum dots (PQDs) on the dielectric properties of a nematic liquid crystal (NLC) mat...

Herein, we report the synthesis of ferroelectric layered perovskite Bi4Ti3O12 (BT4) nanoparticles (NPs) and the temperature-dependent dielectric and electro-optical (especially memory effect) properties of 4-pentyl-4'-cyanobiphenyl (5CB) nematic liquid crystal (NLC) doped with 1 wt % BT4 NPs (i.e. 5CB-BT4 composite) using polarising optical microsc...

The ability of light modulation has proved the liquid crystal (LC) materials as very potential candidates to be exploited in various display as well as non-display devices. The display applications of LC materials includes the display panels of digital watches, pocket calculators, information displays, computer monitors, television displays, virtua...

This work demonstrates the specific sensing of plant-pathogen by using a nematic liquid crystal (NLC) material. Nowadays, plant-pathogen is the main component for lowering crop production, hence its detection is a major concern in food safety and quality purposes. The recent developments of liquid crystal (LC) materials have been remarkable in the...

Recently nanoparticles (NPs) are extensively explored as the dopant in liquid crystal (LC) materials because of their phenomenal properties such as good guest–host interaction and high surface to volume ratio. Keeping this motivation into mind, we have observed the influence of newly synthesized cobalt oxide (CoO) NPs on the dielectric and optical...

Here, we demonstrate experimentally the existence oftemporally variable dielectric behavior of a nematic liquid crystal (NLC), the most widely used liquid crystal (LC) phase among all LCs materials, by mixing dimethylsulphoxide (DMSO) into former. The intermolecular interactions and nanosegregation of the molecular LC structures have influenced th...

In this research article, we have investigated the dielectric properties of a nematic liquid crystal (NLC), namely 4 cyano-4′- pentylbiphenyl (which is commonly known as 5CB), in sample cells of variable thickness. The dielectric behaviour has been studied through a LCR meter in the frequency ranging from 20 Hz to 1 MHz. It was observed that the re...

We report the impact of dispersion of bismuth ferrite nanoparticles (BF-NPs) on the helical structure of a ferroelectric liquid crystal (FLC) in two ways: on the surface and into the bulk of FLC. The optical textural observations of the FLC sample cell with BF-NPs on the surface of the substrate show a remarkable change of three different domains h...

We report the dielectric relaxation spectroscopy and textural observations in surface stabilized FLC (SSFLC), having thickness less than the pitch value of the FLC and non-SSFLC geometries, having thickness of sample cell more than the pitch value of same FLC material, namely SCE-13 to get a deeper understanding of the helicoidal structure at the s...

Liquid Crystals (LCs) are soft materials lying in the midway between solids and liquids which have enjoyed considerable success due to their tremendous display and non-display applications in various areas of science and technology such as physics, chemistry, biology, material science, telecommunication etc. On the other hand, nanotechnology, an em...

Here, we present the effect of copper (II) oxide nanoparticles (nCuO) on dielectric and electro-optical parameters of a newly prepared ferroelectric liquid crystal (FLC) mixture, namely W302. The FLC mixture, comprising of pyrimidine compounds, was characterised through dielectric spectroscopy, differential scanning calorimetry (DSC), polarising op...

Photonic crystals (PCs) have achieved significant attention of researchers due to their ability of self-assembly arrangement. The PCs exhibit physical properties such as photonic bandgaps, high reflectance/transmittance, low loss and lasing in the visible range of wavelengths needed for optical systems of desired performance. For application of the...

The memory behavior in liquid crystals (LCs), although rarely observed, has made very significant headway over the past three decades since their discovery in nematic type LCs. It has gone from a mere scientific curiosity to application in variety of commodities. The memory element formed by numerous LCs have been protected by patents, and some com...

We present a low voltage driven electro-optical memory device fabricated by dispersing nano-sized nickel oxide (nNiO) composed of short length nanorods into a ferroelectric liquid crystal (FLC) host material. The nNiO/FLC composite showed a tremendous decrease in saturation voltage compared to the pristine FLC material along with non-volatile memor...

Here, we report thickness dependence of dielectric and electro-optical parameters in ferroelectric liquid crystals (FLCs) without surface stabilization. The dependence of dielectric and electro-optical parameters on cell thickness is observed by dielectric spectroscopy and electro-optical measurements. The dielectric permittivity ( ) measured by va...

The invention relates to an optical memory device and method for the preparation of the optical memory device based on glycerol, a very common and versatile solvent, mixed deformed helix ferroelectric liquid crystal (DHFLC) having applications in ferroelectric liquid crystal based devices, the said method comprising the steps of forming patterns of...

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 h...

We present the characterization and dielectric spectroscopic investigations of a ferroelectric liquid crystal (PLC) material, namely KCFLC 10S. We experimentally demonstrate the observation of a low frequency dielectric relaxation mode along with Goldstone mode in the smectic C* phase of the FLC material under investigation. The behavior of low fre...

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. T...

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...

We present the characterization and dielectric spectroscopic investigations of a ferroelectric liquid crystal (FLC) material, namely KCFLC 10S. We experimentally demonstrate the observation of a low frequency dielectric relaxation mode along with Goldstone mode in the Smectic C* phase of the FLC material under investigation. The behavior of low fre...

We demonstrate a new class of synthetic colloidal suspensions capable of exhibiting negative polarizabilities, and observe for the first time robust propagation and enhanced transmission of self-trapped light over long distances that would have been otherwise impossible in conventional suspensions with positive polarizabilities. Such light penetrat...

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 wa...

In this article, a newly synthesised ferroelectric liquid crystal (FLC) material, namely LAHS 22, has been characterised. The characterisation of the FLC material has been performed using dielectric relaxation spectroscopy, differential scanning calorimetry and polarisation optical microscopy. We observed an enhancement in the dielectric and electr...

We report the development of a common-path and nonmechanical scanning phase-shifting lateral shearing interferometer based on a homogeneous gap and wedge-shaped gap liquid-crystal (LC) cell. The modified cell consists of semi-reflecting and fully reflecting glass plates with LC material sandwiched between them so that the amount of reflected light...

Thus far, focusing a single beam and combining multi-optical Gaussian beams have become two major methods of locally enhancing output laser intensity. In this paper, we propose a method of generating free space auto-focusing beams by combining multiple one-dimensional Airy beams. By employing split-step beam propagation method, auto-focusing beams...

Thus far, focusing a single beam and combining multi-optical Gaussian beams have become two major methods of locally enhancing output laser intensity. In this paper, we propose a method of generating free space auto-focusing beams by combining multiple one-dimensional Airy beams. By employing split-step beam propagation method, auto-focusing beams...

We observed ionic impurities free memory effect using 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 c...

The collective dielectric relaxation studies have been carried out on nanoparticles/ isotropic fluid mixed ferroelectric liquid crystals (FLCs). It has been observed from the dielectric loss spectra that the mixing of nanoparticles (Graphene Oxide and ZnO) and isotropic fluid (Water) into FLCs possesses two dielectric relaxations in low frequency r...

We present faster display devices based on copper oxide decorated multi-walled carbon nanotubes (MWCNTs) doped ferroelectric liquid crystal (FLC) material. The fastening of the response has been attributed to decrease in rotational viscosity of the FLC material. The ionic impurities were also reduced by doping copper oxide decorated MWCNTs into the...

We present faster display devices based on copper oxide decorated multi-walled carbon nanotubes (MWCNTs) doped ferroelectric liquid crystal (FLC) material. The fastening of the response has been attributed to decrease in rotational viscosity of the FLC material. The ionic impurities were also reduced by doping copper oxide decorated MWCNTs into the...

We demonstrate stable self-trapping and self-induced transparency of light in nano-suspensions with negative polarizabilities. Comparing to colloidal systems with positive polarizabilities, a fivefold increase in transmission ratio is achieved.

Single chain contraction and re-expansion of polystyrene sulfonate: A study on its re-entrant condensation at single molecular level J. Chem. Phys. 131, 231103 (2009) Concentration-dependent two-photon absorption and subsequent excited-state absorption in 4-methoxy-2-nitroaniline J. Appl. Phys. 106, 033511 (2009) Temperature effects on quasi-isolat...

We demonstrate for the first time stable self-trapping and self-induced transparency of light propagating in colloidal nano-suspensions with negative polarizabilities. Comparing to “polystyrene-water”-colloidal systems with positive polarizabilities, a fivefold increase in transmission ratio is achieved.

We report a method for the measurement of nematic liquid crystal (NLC) cell parameters i.e., switching voltage, birefringence, retardation, dielectric anisotropy, average tilt angle and change in refractive index with applied DC voltage to LC material. The proposed method is based on optical interferometry and Fourier transform fringe analysis tech...

We demonstrate self-trapping of light in nonlinear nano-suspensions. In particular, self-induced transparency up to four diffraction lengths is observed in colloidal suspensions with induced negative polarizability.

We demonstrate self-trapping of light in nonlinear nano-suspensions. In particular, self-induced transparency up to four diffraction lengths is observed in colloidal suspensions with induced negative polarizability.

We report optical interferometric studies of a wedge-shaped nematic liquid crystal cell. Interference fringes were observed when a nematic liquid crystal cell was placed in one of the arms of Mach–Zehnder interferometer. In the case of homogenous gap cell, the fringe contrast remained unaffected on applying voltage. However, in the case of wedge-sh...

We demonstrate analytically and experimentally that a circular abruptly autofocusing (AAF) Airy beam can be generated by Fourier-transforming an appropriately apodized Bessel beam whose radial oscillations are chirped by a cubic phase term. Depending on the relation between the chirp rate and the focal distance of the Fourier- transforming lens, it...

We observe optical trapping and manipulation of dielectric microparticles using autofocusing radially symmetric Airy beams. This is accomplished by exploiting either the inward or outward transverse acceleration associated with their chirped wavefronts. We experimentally demonstrate, for the first time to our knowledge, that such Airy beams morph i...

We observed that the doping of alumina nanoparticles (AL-NPs) has suppressed the undesired ionic effect in ferroelectric liquid crystals (FLCs). The pure and AL-NPs doped FLC cells were analysed by means of dielectric spectroscopy and electrical resistivity/conductivity measurements. Dielectric loss spectra confirmed the disappearance of the low-fr...

Observation of non-zero spontaneous polarization in paraelectric phase in multiwalled carbon nanotubes doped deformed helix ferroelectric LC is reported. Electro-optical response, spontaneous polarization, rotational viscosity, dielectric permittivity, dielectric loss factor, and electrical resistance of pure and multiwalled carbon nanotubes doped...

We demonstrate optical trapping and manipulation of C60 nano-aerosols with optical bottle beams. This method based on the Moiré technique can be used for trapping a variety of absorbing nano-particles suspended in air.

We demonstrate optical beam auto-focusing without the need of a focusing lens or nonlinearity. Radial Airy beams with inward and outward accelerations are used and an abrupt transition between Airy and Bessel behavior is observed.

We demonstrate optical beam auto-focusing without the need of a focusing lens or nonlinearity. Radial Airy beams with inward and outward accelerations are used and an abrupt transition between Airy and Bessel behavior is observed.

We demonstrate optical trapping and manipulation of aerosols with an optical bottle beam generated by the moiré techniques. We observe stable trapping and back-and-forth transportation of a variety of absorbing carbon particles suspended in air, ranging from clusters of nanosized buckminsterfullerene C 60 to micrometer-sized carbon powders.

We demonstrate optical trapping and manipulation of C60 nano-aerosols with optical bottle beams. This method based on the Moire technique can be used for trapping a variety of absorbing nano-particles suspended in air.

We present the characterisation and dielectric relaxation spectroscopy of a ferroelectric liquid crystal (FLC), namely KCFLC 7S. It was observed that the studied FLC material possesses the tendency of homeotropic alignment on glass substrates coated with indium tin oxide. A low frequency dielectric mode, along with the Goldstone mode, was observed...

A pronounced memory effect has been observed in cadmium telluride quantum dots �CdTe-QDs� doped ferroelectric liquid crystals �FLCs� by using dielectric and electro-optical methods. The memory effect has been attributed to the charge storage on the CdTe-QDs upon the application of dc bias across the sample cell. The FLC molecules remain in the swit...

The characterization of a newly synthesized deformed helix ferroelectric liquid crystal (DHFLC) namely LAHS18 has been presented. The material LAHS18 has been found to possess ultrashort helical pitch, large optical tilt, high spontaneous polarization and large rotational viscosity. A long-lasting memory effect has been shown in this material by el...

We present the results based on electro-optical properties of zinc oxide nanoparticles (ZnO-NPs) doped ferroelectric liquid crystal (FLC). It is observed that ZnO-NPs-FLC system has low operating voltage and improved optical contrast. The lowering in operating voltage and improvement in optical contrast has been attributed to larger dipole moment o...

The decrease in Goldstone mode relaxation frequency with applied dc electric field in a deformed helix ferroelectric liquid crystal (DHFLC) is observed at room temperature. This decrement in relaxation frequency is observed at very low dc electric fields (below the threshold voltage, i.e. around 2 V). This behaviour is compared with that of convent...

The influence of conducting polymer, poly(3-hexylthiophene) (P3HT), on the memory behavior of ferroelectric liquid crystal material has been investigated by textural, electro-optical, and dielectric spectroscopic methods. It has been observed that the memory effect decreases as concentration of P3HT is increased. The good memory effect has been obs...

Here, we report the polymeric (copolymer of benzene and pentacene) nanoparticles (PNPs) induced vertical alignment in ferroelectric liquid crystals (FLCs). The nanoparticles used in this study have been synthesized via chemical route method. The PNPs have been doped in FLC mixture. It has been observed that pentacene molecules (presented in PNPs us...

The effect of surface anchoring on the optical bistability in deformed helix ferroelectric liquid crystal (DHFLC) has been investigated by electro-optical and textural methods. The threshold voltage studies have been carried out in strongly and weakly treated DHFLC cells. The long lasting memory effect has been observed in weakly treated DHFLC cell...

We report the characterization and photoluminescence (PL) of newly synthesized deformed helix ferroelectric liquid crystal (DHFLC) material having short pitch and high spontaneous polarization. We observed ninefold enhancement in PL intensity in gold nanoparticles doped DHFLC material. This enhancement in the PL intensity has been attributed to the...

We present the results of the fast electro-optic response of multiwalled carbon nanotubes (MWCNTs)-doped deformed helix ferroelectric liquid crystal (DHFLC). The fastening of the response in MWCNTs-doped DHFLC has been attributed to the decrease in rotational viscosity and increase in anchoring energy. The decrease in the former is due to the exper...

The optical memory effect based on glycerol mixed deformed helix ferroelectric liquid crystal (DHFLC) material has been investigated. The observed memory effect has also been compared with the glycerol mixed ferroelectric liquid crystals (FLCs). The observance of memory effect has been verified by experimental data using dielectric spectroscopy, el...

Optical and textural studies have been carried out on special class of ferroelectric liquid crystals (FLCs) known as de Vries electroclinic liquid crystals (ELCs) in conjunction with ethanol (C2H5OH). Ethanol shifts the threshold voltage to a low value of 3 V and nearly doubles the optical tilt in the ELC under study. Addition of ethanol shifts the...

An unusual switching phenomenon in the region outside conducting patterned area in ferroelectric liquid crystal (FLC) containing about 1–2 wt % of water has been observed. The presence of water in the studied heterogeneous system was confirmed by Fourier transform infrared spectroscopy. The observed optical studies have been emphasized on the “spat...

The influence of ethanol ( C ₂ H ₅ OH ) doping in the electroclinic liquid crystal has been investigated using dielectric spectroscopy. A giant shift in ferroelectric ( SmC ^*) to paraelectric (SmA) phase transition has been observed. After analyzing collective relaxation processes, it is confirmed that Curie–Weiss l...

Nonvolatile memory effect based on gold nanoparticles (GNPs) doped deformed helix ferroelectric liquid crystal (DHFLC) has been observed. This observed memory effect has been attributed to electric field induced charge transfer from liquid crystal molecules to the GNPs and the stabilization of helix deformation of DHFLC material, which occurs on th...

The behavior of soft mode range with respect to the temperature width of smectic A (Sm A ) phase has been studied in four different ferroelectric liquid crystal (FLC) materials in the frequency range 10 Hz –10 MHz . The studies have been carried out in a planarly well aligned cells at different temperatures and different bias fields in Sm C<sup>*</...

A wide-range memory effect in deformed helix ferroelectric liquid crystals (DHFLCs) has been investigated by electro-optical and textural methods. A comparative study has been performed on strongly and weakly anchored surfaces of DHFLC cells. The saturation voltage has been compared in both types of cells by studying the variation of tilt angle and...

The dynamics of bistability in deformed helix ferroelectric liquid crystal have been investigated by electro-optical method. The threshold value of the voltage required to switch the molecules of deformed helix ferroelectric liquid crystals (DHFLC) material has been studied by applying triangular wave pulse and texture observation under polarizing...

Dielectric, textural, and electro-optical investigations have been carried out on a material exhibiting de Vries smectic A phase transition in sample cells of various thicknesses. Thickness independent memory effect has been observed in this special class of ferroelectric liquid crystals (FLCs) known as de Vries electroclinic liquid crystals. Unlik...