Other rarer polymorphs of TiO2 are known including anatase, akaogiite, and brookite
. Titanium dioxide (TiO2) is the standard white pigment used principally in paints, paper, and plastics.
, anatase and rutile are three basic crystalline structures of TiO2 (Testino et al., 2007).
We used seven different Ti[O.sub.2] structures: Polyethylene glycol (PEG)-amorph Ti[O.sub.2], amorph Ti[O.sub.2], PEG-brookite, rutile, anatase, amorph bovine serum albumin (BSA), and brookite
titania  or hydrate titania  peaks at 59.2 and 60.6 may be due to titania and acid presence in the sol.
Jolivet, "Synthesis of brookite
Ti[O.sub.2] nanoparticles by thermolysis of Ti[Cl.sub.4] in strongly acidic aqueous media," Journal of Materials Chemistry, vol.
It is noteworthy that no extra peaks corresponding to rutile or brookite
phase were observed [12, 13].
Well-known phases of Ti[O.sub.2] are anatase, rutile, and brookite
. Rutile is a tetragonal (a = 4.5937 [Angstrom], c = 2.9587 A), anatase is also a tetragonal (a = 3.7845 [Angstrom], c = 9.5143 [Angstrom]), and brookite
is an orthorhombic crystal (a = 5.4558 [Angstrom], b = 9.1819 [Angstrom], c = 5.1429 [Angstrom]).
Ti[O.sub.2] can be associated with presence of rutile, which is the most common mineral of titanium dioxide; however, polymorphs rarely include brookite
and anatase, both form unique and distinctive crystals on the earth, and this is typical in felsic rocks .
This compound have three crystalline phases: rutile (tetragonal structure), anatase (octahedral structure), brookite
(orthorhombic structure), which according to the requirement of the electrostatic valence rule, each oxygen atom is shared by three octahedra.
Ti[O.sub.2] is a well-known semiconductor and a versatile compound that exists in three crystalline forms, anatase, rutile, and brookite
[14, 21], which can only be activated with UV light due to its high band gap energy (3.0 eV for rutile phase and 3.2 eV for anatase phase).