Synthesis of Nano-Anatase to Produce Small ETS-10 Crystals for Enhanced Textile Properties

Textile production, properties and its end-use have changed beyond recognition over the last decade.¹ Hence, functionalized textiles present a growing niche in the global textile market² which was estimated in 2005 to be worth $400 billion.³ Coating textiles with nano sized photocatalytic material, titanosilicate ETS-10, would impart useful functionalities, e.g., stain-resistant, odor repellant, bactericidal⁴ and enhanced UV protection⁵ on the composite material.

Typically, small ETS-10 crystals are in the range of ~ 500 - 800 nm, and are synthesized using solid titania (e.g., anatase or P25 a mixture of anatase and rutile) sources.^6,7 However, smaller ETS-10 crystallites are required to generate a smooth uniform surface coating with a highly effective surface area. The rate of dissolution of the anatase is considered to be the rate determining step in ETS-10 crystallization.⁷ Thus, it is hypothesized that by incorporating nano-anatase in ETS-10 synthesis, multiple ETS-10 nucleation points can be generated and anatase dissolution rate would be increased, resulting in the growth of uniform, highly crystalline ETS-10 products with fine particle size less than 500 nm.

Colloidal TiO₂ suspensions with the average hydrodynamic particle diameter of ~ 12 nm has been successfully prepared from titanium isopropoxide.^8,9,10 X-ray powder diffraction analysis of anatase powder obtained by drying these colloidal suspensions in air at low temperatures showed phase-pure anatase with the average crystallite size in the 4 - 5 nm range. Scanning electron microscopy and particle size distribution analysis both confirmed the presence of nano-sized particles in all prepared TiO₂ sols. Preliminary investigations have shown that the size of anatase particles influenced the pH of ETS-10 synthesis mixture, thereby giving rise to impurities such as ETS-4. An optimum pH of ~10.6 has been shown to favor ETS-10 formation.⁷ Based on these facts reaction mixture compositions that would yield highly crystalline ETS-10 materials with fine particle size were investigated.

1          T. L. Vigo; Textile Processing and Properties 11, U.S. Dept of Agriculture, 1994

2          W. Chang, P. Kilduff; Small Business & Technology Development Center, May 2002

3.         B. Mahltig, H. Haufe, H. Bottcher; J. of Mater. Chem. 2005, 15, 4385–4398 

4.         K. Qi, W.A. Daoud, J.H. Xin, C.L. Mak, W. Tang, W.P Cheung; J. Mater. Chem. 2006, 16, 4567 - 4574.

5          W.A. Daoud, S.K. Leung, W.S. Tung, J.H. Xin, K. Cheuk, K. Qi; Chem. Mater. 2008, 20, 1242-   1244

6          L. Lv, Fabing Su, X.S. Zhao; Micropor. Mesopor. Mater. 76, 2004, 113-122

7          J. Rocha, A. Ferreira, Z. Lin, M.W. Anderson;  Micropor. Mesopor. Mater. 23, 1998, 253-263

8          K. Qi, X. Chen, Y. Liu, J.H. Xin, C.L. Mak, W.A Daoud; J. Mater. Chemi. 17, 2007, 3504

9          W.A Daoud, J.H. Xin; Chem.Commun. 16, 2005, 2110

10        K.Qi, W.A Daoud, J.H. Xin, C.L. Mak, W. Tang, W.P. Cheung; J.  Mater. Chem. 16, 2006, 4567- 4574