The structural and optical band gap energy evaluation of nano TiO 2 powders by diffuse reflectance spectroscopy prepared
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ORIGINAL ARTICLE
The structural and optical band gap energy evaluation of nano TiO2 powders by diffuse reflectance spectroscopy prepared via combustion method Pedram Rashidi1 · Misagh Ghamari1 · Mahdi Ghasemifard1 Received: 31 July 2020 / Accepted: 30 September 2020 © Islamic Azad University 2020
Abstract Nanocrystalline TiO2 powders with different optical band gap have been successfully prepared using solution combustion method starting directly from titanium metal. The emphasis is placed on the role of fuel urea on the variations of optical band gap which is obtained from DRS data in the range of 190–1100 nm. The samples were characterized with XRD, FTIR, FESEM, and DRS. It is shown that the powders calcined at 800 ℃ are predominantly anatase and minor rutile according to XRD results where the crystallite size ranges from 13.2 nm to 22 nm. The size of powders can affect the photo catalytic activity of T iO2 where the surface/ volume ratio determines the available sites for electrons to migrate. The micronized aggregated powders composed of sub-particles in the order of less than 100 nm have no preferred morphology based-on FESEM images. FTIR analysis satisfactorily matched with the standard data. The results of diffuse reflectance spectroscopy (DRS) accompanied with mathematical calculations extracted the values of optical direct band gap of TiO2 powders in the range of 3.53 to 3.6 eV which is in the border of UV and Vis part of electromagnetic radiation. Overall, optical band gap and crystallite size can be controlled by fuel in combustion method. Keywords TiO2 · Urea · Band gap · Combustion · Anatase
Introduction Titanium dioxide (titania) is one of the most environmentally compatible, chemically stable, and functionally versatile material. Nanostructured titania has been proven to be a potentially worthwhile material because of possessing splendid features specifically in the photo catalytic applications [1]. Nowadays, nano-titania has been located in the heart of different researches due to non-toxicity, interesting physicochemical properties, and cost effective availability. Many applications of TiO2 especially in photo catalytic uses depends on the value of optical band gap which is a * Misagh Ghamari [email protected] Pedram Rashidi [email protected] Mahdi Ghasemifard [email protected] 1
Nano Laboratory, Faculty of Engineering, Esfarayen University of Technology, Esfarayen, Iran
function different parameters [2]. One of the most important parameters assigns to the synthesis route in which different chemical reactions can alter electronic structure of titanium dioxide products. Among synthesis routes the combustion method has found the prominent role in wet chemical based experiments [3]. Since the final reactions in solution combustion synthesis are exothermic, there is no need to supply extra energy that is a benefit to these kinds of reactions from economic point of view. The final properties of the product can be controlled easily by manipulation of reactant such a
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