Structure, stability and electronic properties of TiO₂ nanostructures

Abstract

PACS 61.46.+w, 71.15.Mb, The structural properties, the stability and the electronic properties of various nanostructures based on the titania layer modifications (anatase and lepidocrocite) are studied using the density-functional-based tightbinding method (DFTB). The anatase nanotubes were found as the most stable nanostructure of TiO 2 . Based on the results of the calculations of the anatase nanostructures a model of their stability was developed. All anatase nanoforms are semiconductors with a direct band gap (~4.2 eV). The lepidocrocite nanotubes are semiconductors with an indirect band gap (~4.5 eV).

Symmetry and models of single-walled TiO2 nanotubes with rectangular morphology

“…We consider here three types of the nanotubes constructed from initial anatase slabs. The 3-layer model of the anatase (101) slab consists of three atomic layers (O-Ti-O), however, its structural optimization results in formation of fluorite-type (111) slab [17,19] in which the symmetry can be attributed to the layer group 72 (P3 1). It is the same for 3-layer slab with both anatase and fluorite structures, although the space symmetry of fluorite TiO 2 bulk crystal is described by cubic space group 225 (F 3 ).…”

“…For 2D structure, a slab model of thermodynamically stable anatase TiO 2 (101) surface [1] was mainly applied, which can be easily organized in double sub-sheets consisting of the two formula units with sixlayer O-Ti-O_O-Ti-O structure with a centered rectangular morphology [13]. Nevertheless, the latter was very scarcely considered for simulation on TiO 2 NTs, during the last three years only [14][15][16], while a number of earlier and recent simulations on TiO 2 NTs were limited by triplelayered O-Ti-O structure, with optimization resulted in a hexagonal fluorite-like morphology [17][18][19][20][21]. This is not only due to computational limitations, , insufficient application of formalism of rotohelical symmetry in ab initio calculations, but also due to a presence of 3-layer fragments in structural units of separate walls in MW TiO 2 NTs [8].…”

“…As to anatase TiO 2 (001) surface, it was found to be considerably less stable than (101) surface [1]. According to theoretical simulations [22,23], the former can be reconstructed to a surface with lepidocrocite structure used for ab initio simulations on the corresponding TiO 2 nanotubes [17,24]. Only SW TiO 2 NTs were simulated so far.…”

The Effect of Gold Nano Particles Compared to Dioxide Titanium Nano Particles on Vital Factors of Isolated Candida albicans in Patients with Oral Candidiasis in Vitro

“…As you know photo catalyst is a material that in light radiation resulted into chemical reaction but itself never changes and just provide proper conditions to perform a reaction [22,23]. Titanium dioxide is in the Nano metrical size of an ideal photo catalyst and the most important reason for the presence of this feature is the ability of absorbing ultra-violet rays [24][25][26][27][28][29].…”

First-principles study of thinTiOxand bulklike rutile nanowires

“…13 Structural, electronic and vibrational properties of titania chains embedded in ETS-10 have been studied using ab initio methods. 14 Moreover, Enyashin et al 15,16 have studied the stability and electronic structure of various TiO 2 nanotubes governed from anatase and lepidocricite layer modifications by using density-functional-based tightbinding method. Futhermore, ab initio calculations are reported that investigates atomic scale 17 as well as the rutile 18 TiO 2 nanowires.…”