Annealing of bimetal doped and pure nanotitania: A comparative analysis

Abstract

Titania (TiO2) is a compound that is both familiar and abundant, having seen many applications in diverse areas such as cosmetics, coatings and water purification. Some common phases of titania are anatase (tetragonal), brookite (orthorhombic) and rutile (tetragonal). These phases occur naturally in minerals and are regularly extracted and separated from said ores. The size of titania particles are also paramount in determining its characteristics and potential application. The smaller the particle gets, the more diverse its potential application can be. With today's focus on nanotechnology, interest in how titania can play a role in this field is being pursued by many scientist and researchers. As a result of this fervor, we see nanosized titania being used in areas previously thought unfeasible, such as electrochromic devices, electronic sensors and photovoltaic cells. The inclusion of titania into these devices produces effects such as lengthening of process cycles and increased efficiency. The fabrication method mentioned above needs to be routinely modified to produce products that are deemed to be ‘nano’ in size, with determining factors such as crystallite/grain size and thickness being given special attention. Nanotitania also gives way to the significance of doping, where previously doping is seen as moderately affective; with nanotitania, it effect is profound and almost radical. Generally, doping in titania is divided into three categories, the first is a pure, undoped titania, the second is a metal-doped titania (Na, Mg, Li, Cr), dubbed a second generation titania, and the third is a nonmetal doped titania (F, Cl, Br), known as the third generation titania. Each doping, at the micron level or below, slightly alter properties such as reactivity and surface area by about 10–20%, or offer no changes, such as seen in the case of doping titania with iron, where no changes occurred in its photocatalytic activity level, while doping nanotitania will increase or decrease properties such as surface area by close to almost 40%.