Preparation, characterization and application of phase-pure anatase and rutile TiO2 nanoparticles by new green route

Abstract

some distinct properties of TiO 2 , among which high redox potential, high chemical stability, low cost, and no toxicity stand out. These properties depend on many factors, such as the crystal structure, crystallite size, particle shape, and specific surface area, which are also strongly dependent on the method of synthesis. In terms of its crystal structure, TiO 2 exists as three important polymorphs: rutile (tetragonal), anatase (tetragonal), and brookite (orthorhombic) [6]. Rutile is the only stable phase; anatase and brookite are metastable at all temperatures and can be converted to rutile after heat treatment at high temperatures. Dependent on structure and particle size, each crystalline phase exhibits different physical properties best suited to different applications. For example, the anatase phase has a band gap of 3.2 eV, which means that it can be activated by UV light illumination. This is one of the reasons why it is often preferred for applications in photocatalysis [7-9]. The photocatalytic activity of TiO 2 originates from the presence of photo-generated electrons (e −) in the conduction band and holes (h +) in the valence band under irradiation with UV light. These holes have high oxidation power, thus they can easily react with adsorbed hydroxide ions to produce hydroxyl radicals, the main oxidizing species that are responsible for the photo-oxidation of organic compounds. The photocatalytic performance of anatase is considered superior to the more stable rutile (3.0 eV); this is attributed to a higher density of localized states and slower charge carrier recombination [10]. On the other hand, it has been reported that the presence of a small fraction of the rutile phase in intimate contact with anatase TiO 2 can improve its photocatalytic performance [11-13]. Pure anatase phase can be synthesized by many methods, such as the hydrothermal method, the sol gel method, the chemical method, and electrodeposition [14-19]. While all these methods have their own important benefits, the

Biogenic Photo-Catalyst TiO2 Nanoparticles for Remediation of Environment Pollutants

“…Therefore, on increasing the temperature from 300 to 800 °C, the band gap energy of the TDO NPs tremendously changes, and this change might be attributed to the crystal defects in the materials. The current results are strongly analogous to reported results . Earlier studies on TiO 2 NP-mediated aloe vera plant extracts estimated band gap energy to be 3.62 eV …”

“…The current results are strongly analogous to reported results. 21 Earlier studies on TiO 2 NP-mediated aloe vera plant extracts estimated band gap energy to be 3.62 eV. 22 …”

Green Synthesis and Applications of ZnO and TiO2 Nanostructures

“…Similarly, Spada et al [ 133 ] used annealing temperature variations of 400–1000 °C (4 h) to control the crystalline phase and the particle size of TiO 2 NPs. The XRD data show that at temperatures above 600 °C, the anatase phase started a transition to the rutile phase, and at temperatures above 1000 °C pure rutile was found.…”

Photocatalytic and antimicrobial efficacy of PVDF/TiO2 membranes fabricated by solution blow spinning

“…It exists mainly in three different crystal forms: rutile (tetragonal), anatase (tetragonal), and brookite (orthorhombic). 31,32 The photocatalytic performance of anatase is considered to be superior to other phases; however, much experimental evidence supports the existence of a synergistic effect of enhancing photocatalytic activity in crystalline TiO 2 containing anatase/rutile. 33 The mixed phase of TiO 2 reduces the recombination of photogenerated electrons and holes, thereby enhancing photocatalytic activity.…”