Carbon nanotubes have useful absorption, photoluminescence (fluorescence), and Raman spectroscopy properties. Spectroscopic methods offer the possibility of quick and non-destructive characterization of relatively large amounts of carbon nanotubes. There is a strong demand for such characterization from the industrial point of view: numerous parameters of the nanotube synthesis can be changed, intentionally or unintentionally, to alter the nanotube quality. As shown below, optical absorption, photoluminescence and Raman spectroscopies allow quick and reliable characterization of this "nanotube quality" in terms of non-tubular carbon content, structure (chirality) of the produced nanotubes, and structural defects. Those features determine nearly any other properties such as optical, mechanical, and electrical properties.
Carbon nanotubes are unique "one-dimensional systems" which can be envisioned as rolled single sheets of graphite (or more precisely graphene). This rolling can be done at different angles and curvatures resulting in different nanotube properties. The diameter typically varies in the range 0.440 nm (i.e. "only" ~100 times), but the length can vary ~10,000 times, reaching 55.5 cm. The nanotube aspect ratio, or the length-to-diameter ratio, can be as high as 132,000,000:1, which is unequalled by any other material. Consequently, all the properties of the carbon nanotubes relative to those of typical semiconductors are extremely anisotropic (directionally dependent) and tunable.
Whereas mechanical, electrical and electrochemical (supercapacitor) properties of the carbon nanotubes are well established and have immediate applications, the practical use of optical properties is yet unclear. The aforementioned tunability of properties is potentially useful in optics and photonics. In particular, light-emitting diodes (LEDs) and photo-detectors based on a single nanotube have been produced in the lab. Their unique feature is not the efficiency, which is yet relatively low, but the narrow selectivity in the wavelength of emission and detection of light and the possibility of its fine tuning through the nanotube structure. In addition, bolometer and optoelectronic memory devices have been realised on ensembles of single-walled carbon nanotubes.
Crystallographic defects also affect the tube's electrical properties. A common result is lowered conductivity through the defective region of the tube. A defect in armchair-type tubes (which can conduct electricity) can cause the surrounding region to become semiconducting, and single monatomic vacancies induce magnetic properties.
The Czech Republic lies mostly between latitudes 48 and 51 N (a small area lies north of 51), and longitudes 12 and 19 E.
The Czech landscape is exceedingly varied. Bohemia, to the west, consists of a basin drained by the Elbe (Czech: Labe) and the Vltava rivers, surrounded by mostly low mountains, such as the Krkonoe range of the Sudetes. The highest point in the country, Snka at 1,602 m (5,256 ft), is located here. Moravia, the eastern part of the country, is also quite hilly. It is drained mainly by the Morava River, but it also contains the source of the Oder River (Czech: Odra).
Water from the landlocked Czech Republic flows to three different seas: the North Sea, Baltic Sea and Black Sea. The Czech Republic also leases the Moldauhafen, a 30,000-square-metre (7.4-acre) lot in the middle of the Hamburg Docks, which was awarded to Czechoslovakia by Article 363 of the Treaty of Versailles, to allow the landlocked country a place where goods transported down river could be transferred to seagoing ships. The territory reverts to Germany in 2028.
Phytogeographically, the Czech Republic belongs to the Central European province of the Circumboreal Region, within the Boreal Kingdom. According to the World Wide Fund for Nature, the territory of the Czech Republic can be subdivided into four ecoregions: the Western European broadleaf forests, Central European mixed forests, Pannonian mixed forests, and Carpathian montane conifer forests.
There are four national parks in the Czech Republic. The oldest is Krkonoe National Park (Biosphere Reserve), and the others are umava National Park (Biosphere Reserve), Podyj National Park, Bohemian Switzerland.
The three historical lands of the Czech Republic (formerly the core countries of the Bohemian Crown) correspond almost perfectly with the river basins of the Elbe (Czech: Labe) and the Vltava basin for Bohemia, the Morava one for Moravia, and the Oder river basin for Czech Silesia (in terms of the Czech territory).