**2. Experimental methods**

TiO2 nanowires (TNWs), nanorods (TNRs) and nanoporous films were grown on ITO glass substrates using hydrothermal method. The hydrothermal synthesis of TNWs, TNRs and nanoporous was carried out in a Teflon-lined stainless steel autoclave. Titanium n-butoxide (TNB) solution was used as precursor for the production of TiO2 films. In a typical synthesis process, TNB (0.5 – 1.0 ml) was used with different amounts of HCl (15 - 23 ml), HNO3 (5 – 15 ml) and deionized water (DI=35-45 ml). Finally, the resulting solution was transferred into an autoclave. Here ITO-coated glass was used as a substrate. The autoclave was sealed and then placed into an electric oven. The synthesis process was carried out for different reaction times as well as temperatures. After completion of the reaction, the autoclave was cooled down to room temperature. Finally, the substrates were thoroughly washed with deionized water, fol‐ lowed by drying overnight at ambient temperature. Nanocrystalline indium tin oxide (ITO) thin films were prepared on glass substrates by ion beam sputter deposition method. The dep‐ osition procedure of nanocrystalline ITO thin films can be found elsewhere [5]. The TiO2 films were characterized by X-ray diffraction (XRD) using Cu Kα radiation (λ=1.54056 Å) at 40 kV and 30 mA, with a Rigaku; RINT 2200VK/PC diffractometer. Transmission through the films was measured using an UV-VIS-NIR spectrophotometer (UV-3150, Shimadzu). The surface morphologies of the TiO2 films were observed by field emission scanning electron microscopy (FE-SEM, S4800, Hitachi). In order to prepare the DSC devices, the TiO2 electrodes were im‐ mersed in ethanol solution containing N-719 dye. Then the dye-anchored TiO2 electrodes were rinsed with ethanol solution and dried in air. The liquid electrolyte was prepared by dissolv‐ ing 0.05 M of iodine (I2) and 0.5 M of potassium iodide (KI) in 10 ml of ethylene glycol. Mean‐ while, platinum film was prepared by ion-beam sputter deposition method and the Ptsputtered ITO/Glass was used as a counter-electrode. Surlyn spacer film with a thickness of 60 μm was used as a spacer. I-V measurements were performed using Keithley High Resistance Meter/Electrometer 6517A at room temperature.

**Figure 1.** XRD patterns of TiO2 films prepared using different volume of HCl. (a) H.T-1[HCl=15 ml; DI=45 ml], (b) H.T-2 [HCl=20 ml; DI=40 ml], (c) H.T-3 [HCl=23 ml; DI=30 ml] and (d) H.T-4 [H.T-2 annealed at 450°C for 30 min]. Here TNB (1

Preparation and Characterization of Nanostructured TiO2 Thin Films by Hydrothermal and Anodization Methods

http://dx.doi.org/10.5772/51254

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**Figure 2.** SEM images of TiO2 films prepared with TNB of 1 ml, HCl of 15 ml, DI of 45 ml, reaction time of 17 h and at a

Figure 1 shows the XRD patterns of TiO2 films prepared using different volumes of HCl. A very strong rutile peak is observed at 2θ of 27.37°, assigned to (110) plane (see Fig.1). Other

ml), reaction time (17 h) and reaction temperature (160°) were kept constant.

reaction temperature of 160°C.
