Quantum Rods Made of Cadmium Selenide (CdSe): Anistropy
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Semiconductor nanocrystals, also known as “quantum dots,” have been intensively studied because of their novel properties caused by quantum confinement and their potential to be used in making electro-optical devices. The colloidal nanocrystals synthesized by wet chemistry methods have in particular drawn much attention because of their chemical processibility and their capability to be incorporated into various matrices such as conducting polymer and biological systems. Studies of CdSe nanocrystals with the wurtzite lattice structure have played an important role in our understanding of quantum confinement and of the growth mechanism of nanocrystals. The recent advances in synthesizing rodlike, disclike, and more exotically shaped nanocrystals have opened a new field to study the shape dependence of their properties. In this article, we review some of the work on CdSe nanorods (or “quantum rods”) that has been done recently in our group. First, we talk about the synthesis of CdSe quantum rods with tightly controlled variable lengths and diameters and second, their optical and dielectric properties. Because the alignment of the quantum rods is desirable for both fundamental studies and applications, we will also cover our work on the formation of the lyotropic nematic phase of these geometrically anisotropic objects in solution, and the large-scale alignment of the quantum rods by taking advantage of the liquid crystalline phase. Then we will finish by briefly discussing some of their potential applications.