Electrophoretic deposition and optical property of titania nanotubes films
Introduction
Titania is an exceptional material and has many important applications in areas such as environmental purification, photocatalyst, gas sensors, and high efficient solar cell [1], [2], [3], [4]. In recent years, titania nanotubes (TNTs) are of particular interest, since they have large surface area and particular tubular structure, moreover, their potential breakthrough in high efficient dye-sensitized solar cells would come true [5], [6], [7].
Electrophoretic deposition (EPD) is an effective method to fabricate thin and thick coatings on conductive substrates. EPD is a process whereby charged particles in an aqueous or non-aqueous suspension are deposited onto a shaped electrode with opposite charge under the action of an applied electric field. It can offer rigid control of film thickness, uniformity and deposition rate. It is especially attractive owing to its low cost of equipment and starting materials. Due to its advantages, EPD has been widely investigated in areas such as structural and functional coatings, as well as forming of superconductors, laminar composites and fuel cells [8].
Despite the large amount of reports on EPD in the literature for various materials, the investigation on the application of this technique to the fabrication of TNTs films hasn't been found up to the present.
The objectives of the present work are to search for the optimal EPD condition of TNTs suspension and to prepare TNTs films with homogeneous porous structure and controllable thickness.
Section snippets
Experimental details
All chemicals are analytical grade and used without further purification. The powders used in the present work are TNTs powders synthesized by ion exchange approach and all nanotubes are open-ended with 3∼5 nm in inner diameter, 8∼12 nm in outside diameter and 200∼400 nm in length [9]. TNTs powders (0.5 g), ethyl alcohol (30 ml) as a solvent, and polyvinyl butyral (PVB, 0.066 g, average molecular weight (Mw) : 19,000) as a dispersant, were put into a 50 ml beaker. Nitric acid (0.1 M) was used to
The dispersion of TNTs suspension
Fig. 1 shows the zeta potential value as a function of the pH value of the TNTs suspension in ethanol. Generally speaking, high absolute zeta potential value indicates a high degree of particle dispersion in the suspension, thus high absolute zeta potential value is mostly desired for the forming of a uniform and steady suspension. It can be seen from Fig. 1 that the isoelectric point (IEP) of the TNTs suspension is at pH = 5.3, where there is no excess surface charge and the zeta potential value
Conclusions
The TNTs films have been fabricated successfully by electrophoretic deposition on Nesa glass. The optimal experimental condition is carried out by using 0.2 wt.% PVB as a dispersant, adjusting the pH value to around 5 and depositing at the applied electric field of 10 V/cm for 2 min. At the applied electric field of 10 V/cm, TNTs film surface has minimum porosity and pore size which is resulted from less amount of evolved hydrogen gas and better particles packing on the cathode during
Acknowledgement
The authors would like to express their gratitude to the support from the National High Technology Research and Development Program of China (863 Program, 2002AA332060).
References (15)
- et al.
Adv. Environ. Sci.
(1997) - et al.
Nature
(1972) - et al.
J. Am. Ceram. Soc.
(1990) - et al.
Nature
(1991) - et al.
J. Cryst. Growth
(2001) - et al.
J. Electrochem. Soc.
(2003) - et al.
J. Photochem. Photobiol., A Chem.
(2004)