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1 Electronic Supplementary Material (ESI) for Chemical Communications. This journal is The Royal Society of Chemistry 2015 Transparent Free-standing Film of 1-D Rutile/Anatase TiO 2 Nanorod Array by One-step Hydrothermal Process Li Cheng Kao, a Chin Jung Lin, b Chung Li Dong, c Chi Liang Chen, d and Sofia Ya Hsuan Liou* a a Department of Geosciences, National Taiwan University, P.O. Box , Taipei 106, Taiwan Fax: ; Tel: ; yhliou@ntu.edu.tw b Department of Environmental Engineering, National Ilan University, 1, Sec. 1, Shen-Lung Road, I-Lan 260, Taiwan c National Synchrotron Radiation Research Center (NSRRC), Hsinchu 30076, Taiwan d Institute of Physics, Academia Sinica, Taipei 11529, Taiwan Electronic Supplementary Information

2 S1 The observation of materials Fig. S1 Images of (a) M-TiO2 detached from FTO substrates, the substrate has no conductibility after the detachment (b) The comparison betweenn M-TiO2 and S2 The hydrothermal method of and morphology measurements The FTO substrates were ultrasonically cleaned in methanol, ethanol, and deionized water for each 10 min, then dried in the air. The samples were synthesized by hydrothermal method containing 30 ml deionized water, 30 ml hydrochloric acid, and 1 ml titanium butoxide (97% Aldrich), as reported elsewhere e (Liu and Aydil, 2009). The experiments were performed at 150 C for 4-20 h in an electric oven. After synthesis, the autoclave was cooled under room temperature for about 20 min and the FTO substratess were rinsed with deionized water and dried in air. Fig. S2 FESEM images of side view of TiO2 nanorod arrays were grown on FTO substrate in 30 ml of deionized water, 30 ml of hydrochloric acid, and 1 ml of titanium butoxide for (a) 4 h and (b) 20 h.

3 S3 The M-TiO2 morphology y observation under different growth time In a typical synthesis process, 0.15 g of Ti foil with two pieces of FTO substrates were added to an autoclave containing 1 ml titanium butoxide, 300 ml deionized water, and 30 ml HCl. The hydrothermal synthesis was conducted at 150 forr 1-4 h in an electric oven. The FTO substrate remained transparent for M-TiO2-1 h, and no TiO2 nanorod arrays weree observed when the growth time was w less than 1 h at 150 C. It was obvious that M-TiO2-2 h was still stuck on FTO, and the FESEM morphology of it was similar to R-TiO2@FTO. After Ti foil dissolving, TiO2 nanorod arrays grew in two-side well aligned, and M-TiO2-3 h could easily detach from the substrate. Up to 4 h, the TiO2 films are densely packed and formed in intact structure. Fig. S3 FESEM images of M-TiO2 under different growth time for r (a) 2 h, (b)) 3 h, and (c) 4; (d) No TiO2 nanorod arrays weree observed on o FTO of M-TiO2-1 h, M-TiO2-2 h was still stuck on FTO, and both M-TiO2-33 h and M-TiO2-4 h were detachable.

4 S4 The TEM imagess of rutile phase TiO2 through one-step o hydrothermal process According to XRD results (Fig. 1 (d)) showed that the diffraction peakss of R-TiO2@FTO agreed well with the tetragonal rutile phasee (JCPDS file no ). TiO2 nanorod arrays were highly oriented with respect too the substrate surface and grows along with the [0 0 1] direction which perpendicular to the substrate, so some s diffraction peaks including (1 1 0) and (1 1 1). However, adding a Ti foil as precursors gradually dissolving the nucleation layer caused the disappeared signal of rutile TiO2 to reappear. The SAED pattern (Figure S4 (c) and (e)) of the rutile nanorod confirmed the tetragonal phase and its i adjacent lattice fringe distances were d 110 = 0.33 nm and d 001 = 0.29, respectively. Accordingg to the research by Andreas A et al. 1, while the reflexes in the diffraction pattern of the bottom of the rodd were spots (Fig. S4 (e)), streaks were observed in the diffraction patterns of the middle m and top part off the nanorod (Fig. S4 (c)). The streaks arised due to elongated rods in reciprocal space which were caused by the small width of the fingers compared to their length. The direction of the streaks is perpendicul lar to the (1 1 0) surface of the fingers, i.e., along the directions. Fig. S4 TEM images of M-TiO2-4 h (rutile phase) (a)) tetragonalal rutile phase TiO2 nanorod grows along with the [0 0 1] direction. HRTEM images of (b) top part of the nanorod and (d) bottom of the rod. SAEDs of (c) streaks in the diffraction patterns of the top and (e) spots in the bottom.

5 S5 Scanning photoelectron microscopy at Ti L-edge Scanning photoelectron microscopy (SPEM) at Ti L-edge was measured at the beamline BL09A at the National Synchrotron Radiation Research Center (NSRRC) in Hsinchu, Taiwan, using a spherical grating monochromater with four interchangeable gratings and the photoelectrons were collected by a hemispherical analyzer with a 16-channel multichannel detector.

6 S6 The oxidation / reduction potential between Ti 3 + and SnO 2 SnO 4H 2e Sn 2H O E Reduction Ti 2H O 2TiO 4H 2e E Oxidation 0.1 SnO 2Ti 2TiO Sn E 0 Since the E 0 demonstrated that this reaction between Ti 3+ andd SnO 2 will be spontaneous under standard condition by calculated the Gibbs freee energy G nfe, where n is the number of moles, and F is the Faraday constant. However, the oxidation / reduction potential was affected by temperature and the concentration of each reactants, needs to calibrate through The Nernst equation. Although 0.15 g Tii foil seemed a few amount mass, the concentration of Ti 3+ which originated from f dissolving Ti foil in the solution (Fig. S5) was almost the same as using 1 ml titanium(iii) chloride solution (12%, SIGMA-ALDRICH) as precursors which also caused Ti 3+ reduced the conductive layers of FTO. Because of Ti Sn and the higher temperature, the corrected potential was largerr than that under standard condition. 2 Fig. S5 The remaining solutionn after the hydrotherm mal methodd with Ti foil.

7 S6 The growth mechanism of M-TiO 2 Liquid Precursor Solid Precursor Ti 4+ as precursor to grow rutile TiO2 on FTO Start dissolving Ti 3+ Rutile TiO 2 Formation SnO 2 as nucleation F T O F T O Rutile Anatase Formation Anatase TiO2 Ti 4+ as precursor to grow rutiletio2 on FTO M-TiO2 detached from FTO, remaining glass Two-sided oriented mixed phase TiO 2 Formation Ti 3+ Ti 3+ reduced SnO2 and also contributed to fabricate TiO2 G l a s s F T O Fig. S5 Growth procedure of M-TiO 2.

8 S8 The degradation of methyl blue (MB) by UV irradiation The M-TiO2 or with active areas of about 1.5 cm was placed vertically in a quartz cell ( cm 3 ) containing 3 mll of 100 mgg L -1 methylene blue, and put inside a Rayonet RPR-100 Photoreactor equipped e with sixteen UV lamps (350 nm, 16 W). The concentration of methylene blue in the solution was measured using UV-Vis spectroscopyy through the intensityy of the 6655 nm absorption peak. The film was immersed in the MB solution and kept in i the dark for 30 min,, and then the UV light was turned on. A first-order rate model,, effectively describes the photocataly ytic degradation of thee methylenee blue solution, where k obs is the observed rate constant. m 2 Fig. S6 The degradation of MB by M-TiO2. References 1. A. Wisnet, S. B. Betzler, R. V. Zucker, J. A. Dorman, P. Wagatha, S. Matich, E. Okunishi, L. Schmidt-Mende, C. Scheu, Cryst. Growth Des., 2014, 14, S. G. Bratsch, J. Phys. Chem. Ref., 1989, 18, 1.