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