Available online at www.sciencedirect.com Journal of the European Ceramic Society 31 (2011) 1067–1074 Original Article Inkjet printing of photocatalytically active TiO 2 thin films from water based precursor solutions Melis Arin a , Petra Lommens a , Nursen Avci b , Simon C. Hopkins c , Klaartje De Buysser a , Ioannis M. Arabatzis d , Ioanna Fasaki d , Dirk Poelman b , Isabel Van Driessche a,∗ a SCRIPTS, Department of Inorganic and Physical Chemistry, Ghent University, Krijgslaan 281 (S3), 9000 Ghent, Belgium b LUMILAB, Department of Solid State Sciences, Ghent University, Krijgslaan 281 (S1), 9000 Ghent, Belgium c Department of Materials Science and Metallurg, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ, United Kingdom d NanoPhos SA, PO Box 519, Science & Technology Park of Lavriou, Lavrio 19500, Attica, Greece Received 27 August 2010; received in revised form 10 December 2010; accepted 21 December 2010 Available online 28 January 2011 Abstract In this work, aqueous chemical solution deposition route suited for inkjet printing is used for the synthesis of photocatalytically active TiO 2 coatings. Environmentally friendly precursor solutions with electromagnetic ink-jet printing, allows cheap and simple processing of TiO 2 films on glass. The hydrolysis reaction of water sensitive titanium alkoxide (Ti-alkoxide) precursor is controlled by adding complexing agents as citric acid and triethanolamine prior to water addition, and aqueous stable solutions are achieved. The pH of the solutions is brought to neutral to guarantee flexible processing, avoid damage to substrates and equipment. Solution parameters are adapted to obtain optimal gelation conditions and good jettability. The influence of processing parameters on the phase formation and surface morphology is studied by thermogravimetric analysis and differential thermal analysis (TGA/DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The photocatalytic activity of the films is evaluated by the degradation of methyl orange. © 2011 Elsevier Ltd. All rights reserved. Keywords: Films; Chemical properties; Sol–gel processes; TiO 2 ; Inkjet printing 1. Introduction In recent years, titanium dioxide, a high energy band gap semiconductor, has received considerable interest due to its pho- tocatalytic activity under UV-irradiation. As TiO 2 layers are transparent and colorless, more and more applications become available for TiO 2 . Thin TiO 2 coatings can be used to cre- ate self-cleaning, antifogging, and superhydrophilic surfaces. 1–7 Combined with its high refractive index, it is one of the most promising wide band gap semiconductors for use in optoelec- tronics such as solar cells. 1,8–10 TiO 2 films prepared by chemical solution deposition methods are attracting much attention, because of the relatively simple production of large area, high purity films at low cost and high scalibility. 11–14 At this time, most of the sol–gel chemistry lit- ∗ Corresponding author. Tel.: +32 9 264 44 33; fax: +32 9 264 49 83. E-mail address: Isabel.VanDriessche@UGent.be (I. Van Driessche). erature on TiO 2 focuses on controlled hydrolysis in alcoholic media. 15–19 However, industrial demands encourage the devel- opment of water based precursor designs. The difficulty lies in the high reactivity of Ti-alkoxide towards H 2 O. In organic media, hydrolysis is often induced by adding small amounts of H 2 O. Yet, we want to avoid this hydrolysis and the resultant precipitation by blocking the hydrolysis reaction in pure aque- ous media, using complexing ligands as stabilizing agents. We choose triethanolamine (TEA) and citric acid (CA) which are used in cosmetics and food industry respectively and thus are environment-friendly. So far there are a limited number of publi- cations on aqueous TiO 2 solutions starting from alkoxides such as the study of Ohya et al. where different complexing agents like amines and carboxylic acids were used to create precursor solu- tions suited for spincoating on glass. 4 In Sheng’s study, 20 H 2 O was used in high molar ratios for the hydrolysis of Ti alkoxide, however peptization was done with HNO 3 at very low pH values (1–2). This is in line with a number of studies, 15–20 where the pH levels of the solutions necessary to stabilize Ti 4+ ion, are below 0955-2219/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jeurceramsoc.2010.12.033