The parallel alignment of an ensemble of colloidal nanorods may unleash their application as the optically anisotropic constituent in polarized fluorescent sheets or polarization-selective detectors. Here, we demonstrate that full alignment of colloidal CdSe/CdS nanorods in suspension can be achieved by applying AC electric fields. Alignment is monitored by the concurrent change of the optical transmission of the dispersion. By comparing the transmission measurements to a theoretical model encompassing both the permanent and induced dipole moments of the nanorods, we can attribute the alignment to the interaction between the electric field and the nanorod's permanent dipole moment. The permanent dipole moment, relaxation time, absorption anisotropy and critical frequency of the CdSe/CdS nanorods are determined. In addition, we show that the regime of full alignment enables the direct determination of the anisotropic absorption of CdSe/CdS nanorods. We find that the anisotropy in absorption for the CdSe dot is similar to that of the CdS rod, which we attribute to the similarity in dielectric constant and electric field in both materials.

We demonstrate the fabrication of a large-scale device allowing for electrical switching of polarized light with a polarization ratio of 0.45 over a 1.5 cm 2 area. To achieve this, silica-coated semiconductor nanorods were embedded in polymeric nanofibers by electrospinning. The uniaxial extensional flow experienced by the particles induces alignment of the nanorods within the nanofibers. A subsequent parallel alignment of the nanofibers themselves results in a large and flexible film of massively aligned nanorods that can conveniently be processed further. We demonstrate this by integrating the aligned nanofibers in a liquid crystal cell with a polarizer where applying a voltage allows switching the emitted light on and off.

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A wavelength shift of the photonic band gap of 141 nm is obtained by electric switching of a partly polymerized chiral liquid crystal. The devices feature high reflectivity in the photonic band gap without any noticeable degradation or disruption and have response times of 50 µs and 20 µs for switching on and off. The device consists of a mixture of photo-polymerizable liquid crystal, non-reactive nematic liquid crystal and a chiral dopant that has been polymerized with UV light. We investigate the influence of the amplitude of the applied voltage on the width and the depth of the reflection band.

Semiconductor nanorods have anisotropic absorption and emission properties. In this work a hybrid luminescent layer is produced based on a mixture of CdSe/CdS nanorods dispersed in a liquid crystal that is aligned by an electric field and polymerized by UV illumination. The film emits light with polarization ratio 0.6 (polarization contrast 4:1). Clusters of nanorods in liquid crystal can be avoided by applying an AC electric field with sufficient amplitude. This method can be made compatible with large-scale processing on flexible transparent substrates. Thin polarized light emitters can be used in LCD backlights or solar concentrators to increase the efficiency

This paper demonstrates a thin and transparent reflector film for the near infrared, based on chiral nematic liquid crystal (CLC) polymers. Two films reflect almost 50% of unpolarized incident light from 730 to 820 nm and from 880 to 1030 nm, while remaining completely transparent in the visible region with transmittance > 90 % . An efficient window uses the combination of two reflectors. After exposing two window-cubes for 2 h to direct sunlight, the temperature inside the cube with reflector windows was 4°C lower than in cube with plain windows. This reveals that the infrared (IR) reflectors can effectively control the indoor temperature. These films, which are 8 µm in thickness, can be detached from the glass substrates and used as a free-standing film, or be attached to a flexible optical foil or a solid window. The foils can be applied in buildings, offices, and automobiles to statically reduce the energy consumption required for air conditioning or lighting. The free-standing foils show acceptable resistance to polar protic solvents and are thermally stable up to 100°C.

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Methanol contamination of alcoholic drinks can lead to severe health problems for human beings including poisoning, headache, blindness, and even death. Therefore, having access to a simple and inexpensive way for monitoring beverages is vital. Herein, a portable, low cost, and easy to use sensor is fabricated based on the exploitation of chiral nematic liquid crystals (CLCs) and a textile grid for detection of methanol in two distinct alcoholic beverages: red wine and vodka. The working principle of the sensor relies on the reorientation of the liquid crystal molecules upon exposure to the contaminated alcoholic beverages with different concentrations of methanol (0, 2, 4, and 6 wt %) and the changes in the observed colorful textures of the CLCs as well as the intensity of the output light. The proposed sensor is label free and rapid.