Highly Crystalline Nanoparticle Suspensions for Low-Temperature Processing of TiO2 Thin Films

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• 作者：Jonathan Watté ; Petra Lommens ; Glenn Pollefeyt ; Mieke Meire ; Klaartje De Buysser ; Isabel Van Driessche
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：May 25, 2016
• 年：2016
• 卷：8
• 期：20
• 页码：13027-13036
• 全文大小：647K
• 年卷期：0
• ISSN：1944-8252

文摘

In this work, we present preparation and stabilization methods for highly crystalline TiO₂ nanoparticle suspensions for the successful deposition of transparent, photocatalytically active TiO₂ thin films toward the degradation of organic pollutants by a low temperature deposition method. A proof-of-concept is provided wherein stable, aqueous TiO₂ suspensions are deposited on glass substrates. Even if the processing temperature is lowered to 150–200 °C, the subsequent heat treatment provides transparent and photocatalytically active titania thin layers. Because all precursor solutions are water-based, this method provides an energy-efficient, sustainable, and environmentally friendly synthesis route. The high load in crystalline titania particles obtained after microwave heating opens up the possibility to produce thin coatings by low temperature processing, as a conventional crystallization procedure is in this case superfluous. The impact of the precursor chemistry in Ti⁴⁺-peroxo solutions, containing imino-diacetic acid as a complexing ligand and different bases to promote complexation was studied as a function of pH, reaction time and temperature. The nanocrystal formation was followed in terms of colloidal stability, crystallinity and particle size. Combined data from Raman and infrared spectroscopy, confirmed that stable titanium precursors could be obtained at pH levels ranging from 2 to 11. A maximum amount of 50.7% crystallinity was achieved, which is one of the highest reported amounts of anatase nanoparticles that are suspendable in stable aqueous titania suspensions. Decoloring of methylene blue solutions by precipitated nanosized powders from the TiO₂ suspensions proves their photocatalytic properties toward degradation of organic materials, a key requisite for further processing. This synthesis method proves that the deposition of highly crystalline anatase suspensions is a valid route for the production of photocatalytically active, transparent films on heat-sensitive substrates such as polymers.