Titanium dioxide (B)
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Titanium dioxide (B) or TiO2(B) is the monoclinic allotrope of titanium dioxide. The mineral is found in weathering rims on tektites and perovskite and as lamellae in anatase from hydrothermal veins and has a density lower than that of the other three allotropes.

In the laboratory anatase can be converted in a hydrothermal route to TiO2(B) nanotubes and nanowires [1] which are of potential interest as catalytic supports and photocatalysts. For this to happen anatase is mixed with 15M sodium hydroxide and heated at 150 °C for 72 hours. The reaction product is washed with dilute hydrochloric acid and heated at 400 °C for another 15 hours. the yield of nanotubes is quantitative and the tubes have an outer diameter of 10 to 20 nanometres and an inner diameter of 5 to 8 nanometres and have a length of 1 micrometres. A higher reaction temperature (170 °C) and less reaction volume gives the corresponding nanowires.
referneces:
    * [1] "Stem Cell Attachment to Layer-by-Layer Assembled TiO2 Nanoparticle Thin Films" Dinesh S. Kommireddy, Shashikanth M. Sriram, Yuri M. Lvov, David K. Mills, Biomaterials, 2006, 27, 4296-4303.

    * [2] "Layer-by-Layer Assembly of TiO2 Nanoparticles for Stable Hydrophilic Biocompatible Coatings” Dinesh S. Kommireddy, Amish A. Patel, Tatsiana G. Shutava, David K. Mills, Yuri M. Lvov. Journal of Nanoscience and Nanotechnology, 2005, 5, 1081-1087.

    * [3] Nanotubes with the TiO2-B structure Graham Armstrong, A. Robert Armstrong, Jesús Canales and Peter G. Bruce Chemical Communications, 2005, (19), 2454 - 2456 Abstract

    * [4] Titanium dioxide (TiO2) as photocatalyst, Green Quest Technology Inc.[1]