Search query: Semiconductor Nanorod Liquid Crystals

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abstract: Rodlike molecules form liquid crystalline phases with orientational order and positional disorder. The great majority of materials in which liquid crystalline phases have been observed are comprised of organic molecules or polymers, even though there has been continuing and growing interest in inorganic liquid crystals. Recent advances in the control of the sizes and shapes of inorganic nanocrystals allow for the formation of a broad class of new inorganic liquid crystals. Here we show the formation of liquid crystalline phases of CdSe semiconductor nanorods. These new liquid crystalline phases may have great importance for both application and fundamental study.
author_names: L Li

Joost Walda

Liberato Manna

A Paul Alivisatos
title: Semiconductor Nanorod Liquid Crystals
year: 2002

author_names: L Li

A Paul Alivisatos
title: Semiconductor nanorod liquid crystals and their assembly on a substrate
year: 2003

abstract: Abstract In this project we developed a new type of material system for use in opto electronic applications. It consists of an array of nanorods. The nanorods are quantum semiconductor structures with high fluorescence quantum yields, and with their bandgap emission energy controlled by the diameter of the rod. These quantum rods are coated with a monolayer of organic surfactant which renders them highly soluble in organic liquids. We demonstrated a method by which these nanorods can be deposited from solution in the presence of an electric field, such that the nanorods are oriented perpendicularly to the substrate.
author_names: A Paul Alivisatos
title: Electro Optic Materials Based Upon Inorganic Semiconductor Nanorod Liquid Crystals
year: 2006

abstract: Photonic crystals (PCs) have many applications in order to control light wave propagation. A novel type of two dimensional anisotropic PC is investigated band gap and optical properties as a hollow semiconductor nanorod with nematicliquid crystals (LC) The PC structure composed of an anisotropic nematicLC in semiconductor square hollow nanorod is designed using the plane wave expansion (PWE) method and finite difference time domain (FDTD) method. It has been used 5CB (4 pentyl 4` cyanobiphenyl) as LC core, and Tellurium (Te) as square hollow nanorod material.The PC with hollow Tenanorod with nematicLC is compared with the PC with solid Tenanorodand the PC with hollow Tenanorod.
author_names: Filiz Karaomerlioglu

Sevket Simsek

Amirullah M Mamedov

Ekmel Ozbay
title: 2D Anisotropic Photonic Crystals of Hollow Semiconductor Nanorod with Liquid Crystals
year: 2013

abstract: We studied the electro optical property and photorefractive effects in a semiconductor CdSe nanorod doped neamtic liquid crystal [NLC] system. The nonlinear index coefficient is measured to be n2=2.05x10 2cm2/W, which is 10 times larger than that of an equivalent pure liquid crystal system. Electro optical switching investigation shows that the Freedericksz transition voltage of this system is also noticeably lower than that of un doped NLC. These enhanced electro and nonlinear optical properties are attributed to the photoconductivity of CdSe nanorods and the enlarged electric conductivity and dielectric anisotropies of the doped system. An AC field assisted photorefractive effect in CdSe nanorod doped liquid crystal system has also been studied.
author_names: Y Williams

Kan Chan

Jae-Hong Park

Iam-choon Khoo

B A Lewis

Thomas E Mallouk
title: Electro optical and nonlinear optical properties of semiconductor nanorod doped liquid crystals
venue: SPIE Optics Photonics
year: 2005

abstract: Monolayer WS2 has interesting properties as a direct bandgap semiconductor, photocatalyst, and electrocatalyst, but it is still a significant challenge to prepare this material in colloidal form by liquid phase exfoliation (LPE) Here, we report the preparation of 1 2 layer semiconducting WS2 nanosheets in a yield of 18 22 wt by a modified LPE method that involves preintercalation with substoichometric quantities of n butyllithium. The exfoliated WS2 nanosheeets are n type, have a bandgap of ~1.78 eV, and act as a cocatalyst with CdS nanorods in photocatalytic hydrogen evolution using lactate as a sacrificial electron donor. Up to a 26 fold increase in H2 evolution rate was observed with WS2/CdS hybrids compared with their pure CdS counterpart, and an absorbed photon quantum yield (AQE) of >60% was measured with the optimized photocatalyst.
author_names: Danyun Xu

Pengtao Xu

Yuanzhi Zhu

Wenchao Peng

Yulian Li

Guoliang Zhang

Fengbao Zhang

Thomas E Mallouk

Xiaobin Fan
title: High Yield Exfoliation of WS2 Crystals into 1 2 Layer Semiconducting Nanosheets and Efficient Photocatalytic Hydrogen Evolution from WS2/CdS Nanorod Composites.
venue: ACS applied materials interfaces
year: 2018

abstract: Photoalignment technology provides high alignment quality with an exceptional control over the local director of liquid crystals. Because of the reorientation ability of sulfonic azo dye molecules, they offer high azimuthal and polar anchoring energy with a low pretilt angle for the orientation of liquid crystals and liquid crystal composites. In this work, we make use of this approach to align thin film composites of light emitting semiconductor nanorods dispersed in a liquid crystal polymer into both one dimensional and two dimensional microscale patterns. After unidirectional alignment, the patterns are fabricated by a second irradiation with different polarization azimuth and the employment of a photomask. Fluorescence micrographs reveal the nanorod pattern alignment in domain sizes down to 2 mm. Apart from demonstrating the possibility of controlling the orientation of anisotropic nanocrystals with strongly polarized emission on microscopic scale, our results are promising for the fabrication of complex nanostructures for photonic applications.
author_names: Julian Schneider

Wanlong Zhang

Abhishek K Srivastava

Vladimir G Chigrinov

H S Kwok

Andrey L Rogach
title: Photoinduced Micropattern Alignment of Semiconductor Nanorods with Polarized Emission in a Liquid Crystal Polymer Matrix.
venue: Nano letters
year: 2017

abstract: This report describes how doping liquid crystals (LC) with rod like hexagonal semiconductor nanoprisms alters the dielectric and elastic properties of the composites as compared with a pristine nematic liquid crystal (NLC) Cadmium sulfide nanorods were synthesized via the solvothermal process and blended with a NLC. Nanorods were highly miscible with NLC and produced a topological defect free texture up to a certain limit. A good dark state was achieved during the homeotropic configuration of the cell within that limit. Appreciable changes in splay and bend elastic constants of the LCs were observed after blending with nanorods. Long range order was established in the hybrid system, and consequently the anisotropy was increased. The threshold voltage decreased dramatically by ?31% Dielectric study revealed a high frequency mode, which might be due to anchoring of the LC with nanorods.
author_names: Prasenjit Nayek

Santanu Karan

Sudarshan Kundu

Seung Hee Lee

Sudeshna Das Gupta

Soumen Kumar Roy

Subir Kumar Roy
title: Effect of cadmium sulfide nanorod content on Freedericksz threshold voltage, splay and bend elastic constants in liquid crystal nanocomposites
year: 2012

abstract: ZnO nanorod polymer hybrids (i.e. ZnO nanorods coated with a block copolymer with a short anchor block (dopamine) and a longer solubilizing block of polystyrene (PS) form liquid crystalline (LC) phases if they are dispersed at high concentration e.g. in a PS oligomer matrix. Due to the high mobility of the low T(g) matrix the nanorod polymer hybrids show a switching behavior under an applied AC electric field. Hence, the orientation of the nanorod mesogens can be changed from planar (parallel to the substrate) to homeotropic (perpendicular) in full analogy to the switching of low molecular liquid crystals in an electric field. Dielectric measurements show that such a switching is mainly due to the cooperative LC behavior, because the rods themselves exhibit only a very small effective dipole moment. The process can be investigated by polarizing microscopy. SEM images show the orientations of the individual nanorods, which correspond to the Fredericks transition well known for liquid crystals aligned in an electric field. This was the first time such a transition could be visualized by electron microscopy due to the large nanorod mesogens. The observation is interesting to orient nanorods perpendicular to an electrode and can help to improve optoelectronic devices.
author_names: Matthias Zorn

Muhammad Nawaz Tahir

Bjorn Bergmann

Wolfgang Tremel

Christos Grigoriadis

George Floudas

Rudolf Zentel
title: Orientation and Dynamics of ZnO Nanorod Liquid Crystals in Electric Fields.
venue: Macromolecular rapid communications
year: 2010

abstract: Biominerals such as bones and teeth have elaborate nanostructures composed of aligned anisotropic hydroxyapatite (HAp) nanocrystals, which results in excellent mechanical properties. Construction of such ordered structures of HAp nanocrystals in synthetic materials is challenging. Recently, we reported that HAp nanorod based colloidal liquid crystals could be obtained. In the present study, the static structure and dynamics of liquid crystalline (LC) colloidal dispersions of HAp nanorods are investigated by using small angle X ray scattering (SAXS) and X ray photon correlation spectroscopy (XPCS) The SAXS results reveal that the interparticle distance decreases with increasing HAp concentration, phHAp, and the decrease of the interparticle distance for the short axis direction is significantly smaller in the LC phase than the interparticle distance in the isotropic phase. In the dynamical studies of the LC phase using XPCS, we observe the diffusive motion of the HAp colloids, with the diffusion coefficient being dependent on the wave number. The diffusive motion slows down with increasing phHAp. We observe anisotropic dynamics after long term storage (160 days after sealing) whereas only isotropic dynamics are observed in the initial XPCS measurements after short term storage (14 days after sealing) Moreover, we have found that the dynamics slows down with increasing storage time.
author_names: Taiki Hoshino

Masanari Nakayama

So Fujinami

Tomotaka Nakatani

Yoshiki Kohmura

Takashi Kato
title: Static structure and dynamical behavior of colloidal liquid crystals consisting of hydroxyapatite based nanorod hybrids.
venue: Soft matter
year: 2019