Visible light responsive TiO2 nanotubes synthesized by electrochemical anodization method

Elizabeta Stojcheva¹, Metka Benčina²*, Ita Junkar², Tomaž Lampe³, Matjaz Valant^{4, 5}, Veronika Kralj-Iglič³, Aleš Iglič^{2, 6}

¹Laboratory of Biophysics, Faculty of Electrical Engineering, University of Ljubljana, Tržaška 25, SI 1000 Ljubljana, Slovenia

²Jožef Stefan Institute, Department of Surface Engineering and Optoelectronics, Jamova 39, SI-1000 Ljubljana, Slovenia

³Laboratory of Clinical Biophysics, Faculty of Health Sciences, University of Ljubljana, Zdravstvena 5, SI-1000 Ljubljana, Slovenia

⁴Materials Research Laboratory, University of Nova Gorica, Vipavska 13, SI-5000 Nova Gorica, Slovenia

⁵Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, China

⁶Laboratory of Clinical Biophysics, Faculty of Medicine, University of Ljubljana, Zaloška 9 5, SI-1000 Ljubljana, Slovenia

Adv. Mater. Lett., 2018, 9 (10), pp 708-714

DOI: 10.5185/amlett.2018.2024

Publication Date (Web): Jul 18, 2018

E-mail: metka.bencina@ijs.si

Full Article

Abstract

The photocatalytic activity of TiO₂ nanotubes (NTs) makes these materials promising candidates for a variety of applications, including photocatalytic degradation, water splitting and biomedical devices. The large band gap of TiO₂ (anatase ∼3.2 eV; rutile ∼ 3.0 eV) requires excitation with UV light, which accounts for only a small fraction of solar light. In order to increase the light absorption in the visible region, reduction of the band gap is required. Here, TiO₂ nanotubes (NTs) were fabricated by electrochemical anodization of Ti foil. Scanning electron microscopy (SEM), X-ray diffraction analysis (XRD) and X-ray photoemission spectroscopy (XPS) were used to determine morphology, crystal structure and surface composition of the TiO₂ NTs. Different synthesis conditions influenced TiO₂ NTs properties that allowed the tuning of the band gap. UV-Vis analysis of 61.54 µm long NTs showed light absorption over the whole visible range, while NTs with the length up to 0.21 µm are able to absorb only UV light. 61.54 µm long NTs exhibited band tailing up to 1.43 eV.