Photonic band gap materials have the ability to modulate light. When they can be dynamically controlled beyond static modulation, their versatility improves and they become very useful in scientific and industrial applications. The quality of photonic band gap materials depends on the tunable wavelength range, dynamic controllability, and wavelength selectivity in response to external cues. In this paper, we demonstrate an electrically tunable photonic band gap material that covers a wide range (241 nm) in the visible spectrum and is based on a monodomain blue-phase liquid crystal stabilized by nonmesogenic and chiral mesogenic monomers. With this approach, we can accurately tune a reflection wavelength that possesses a narrow bandwidth (27 nm) even under a high electric field. The switching is fully reversible owing to a relatively small hysteresis with a fast response time, and it also shows a wider viewing angle than that of cholesteric liquid crystals. We believe that the proposed material has the potential to tune color filters and bandpass filters.

conquered the large-area display market owing to its advantages such as higher resolution and longer lifetime, but faced challenges from OLED devices in terms of module thickness, response time, and vivid colors. [1] The traditional LCD technology uses blue light-emitting diodes (LEDs) coupled with a yellow phosphor to originate a white light which is transmitted through an assembly of devices comprising polarizers, thin-film transistor array, liquid crystals, and color filters. [2] However, the wide transmission through the color filters and broad emission spectrum of yellow phosphor practically inhibits the realization of wider color gamut in such LCD devices. [3] Semiconductor quantum rods (QRs), owing to their higher brightness, [4] color purity, [5] and polarized light emission [6] features, are lending prominent prospects for their application in display technology. The use of quantum dots in the backlight unit in the form of quantum-dot enhancement film has already been demonstrated [7] ; however, the emission from these spherical particles is isotropic. A unidirectional aligned array of QRs coupled with LCD backlight can be foreseen as a viable option to attain wider color gamut and light polarization. [8] A polarized blue light coming from either laminated conventional polarizer or in-cell coated polarizer can stimulate the QRs to provide narrow red and green polarized emission (Figure 1). This can result in reduced color crosstalk, and hence LCD with high color gamut and contrast ratio can be realized.The alignment of QRs is crucial to attain maximum polarized light emission. Several approaches have been demonstrated in the past on this pathway such as by utilizing photoalignment technology, [9] mechanical rubbing, [10] assembly in liquid crystal defects, [11] and solvent evaporation-assisted assembly. [12] Furthermore, QRs embedded in nanofibers sheets using electrospinning [13] and mechanical stretching of polymer film [14] have been reported with higher degree of alignment. The use of external electric field has been well known to arrange QRs as both parallel [15,16] and perpendicular [17] to the substrate. Herein, we report a simplistic approach for unidirectional alignment of CdSe/CdS QRs by utilizing external electric field after mixing in solvent-based reactive mesogen (RM). The QRs showed higher Harnessing the unique polarized light emission characteristic from semiconductor quantum rods (QRs) necessitates their large-area unidirectional alignment. Herein, the aligned assembly of CdSe/CdS QRs is demonstrated by fabricating a functional film on a micrometer-spaced interdigitated electrodes substrate over an area of ≈1.3 cm 2 . The external electric field is used to control the position and orientation of QRs which is later frozen by the polymerization of reactive mesogen under the exposure of UV light.Under the fluorescence microscope, a judicious change in the QRs emission intensity with the polarizer axis positioned parallel and perpendicular to the alignment direction suggests the optica...

Self-assembled and surface decorated PANI nanotubes with rectangular hallow core with high electrical and dielectric properties.

We report on the preparation and physical characterization of the colloidal suspension of conducting polyaniline (PANI) nanofibres and a nematic liquid crystal (5CB). The ac electrical conductivity anisotropy increases significantly and the rotational viscosity decreases with increasing wt. % of PANI nanofibres, while other physical properties such as birefringence, dielectric anisotropy, splay, and bend elastic constants are changed moderately. The high conductivity anisotropy of liquid crystal nano-composites is very useful for magnetically steered liquid crystal-nanofibre switch.

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We prepared nanocomposites of a nematic liquid crystal and nanofibers of a conducting polymer (polyaniline). All the nanocomposites exhibit a discontinuous surface anchoring transition from planar to homeotropic in the nematic phase on a perfluoropolymer coated surface with a thermal hysteresis (≈ 5.3 °C). We observe a relatively large bistable conductivity and demonstrate a light driven switching of conductivity and dielectric constant in dye doped nanocomposites in the thermal hysteresis (bistable) region. The experimental results have been explained based on the reorientation of the nanofibers driven by the anchoring transition of the nematic liquid crystal. We show a significant enhancement of the bistable temperature range (≈ 13 °C) by an appropriate choice of compound in the binary system.

We have demonstrated an electrically tunable less polarization sensitive and fast response nanostructured polymer dispersed liquid crystal (nano-PDLC) diffraction grating. Fabricated nano-PDLC is optically transparent in visible wavelength regime. The optical isotropic nature was increased by minimizing the liquid crystal droplet size below visible wavelength thereby eliminated scattering. Diffraction properties of in-plane switching (IPS) and fringe-field switching (FFS) cells were measured and compared with one another up to four orders. We have obtained a pore-type polymer network constructed by highly interlinked polymer beads at which the response time is improved by strong interaction of liquid crystal molecules with polymer beads at interface. The diffraction pattern obtained by transparent nano-PDLC film has several interesting properties such as less polarization dependence and fast response. This device can be used as transparent tunable diffractor along with other photonic application.

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