A novel cation-binding TiO 2 nanotube substrate for electro- and bioelectro-catalysis

• Published in: Electrochemistry communications Vol. 7; no. 10; pp. 1050 - 1058
• Main Authors: Bavykin, D.V., Milsom, E.V., Marken, F., Kim, D.H., Marsh, D.H., Riley, D.J., Walsh, F.C., El-Abiary, K.H., Lapkin, A.A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2005
• Subjects: Catalysis; Cytochrome c; Ethanol; Meldola’s blue; Nanotubes; Sensors; TiO 2; Cytochrome c; Ethanol; Meldola’s blue; Nanotubes; Catalysis; Sensors; TiO 2
• ISSN: 1388-2481; 1873-1902
• DOI: 10.1016/j.elecom.2005.07.010

TiO 2 nanotubes (8–20 nm outer diameter and 3–5 nm inner diameter) grown via alkaline hydrothermal synthesis are characterised and compared to 6 nm diameter TiO 2 (anatase) nanoparticles. Zeta potential, voltammetric, and titration experiments reveal that, in contrast to anatase nanoparticles (p.z.c. ca. 6), TiO 2 nanotubes carry a stronger negative surface charge (p.z.c. ca. 3, acidic protons ca. 2 × 10 −3 mol g −1, electrostatic cation adsorption sites in neutral solution ca. 7 × 10 −5 mol g −1) and, under neutral conditions, offer electrostatic binding sites for cations. When immobilised onto an inert boron-doped diamond substrate, TiO 2 nanotubes show electrochemical reactivity due to reversible Ti(IV) reduction, which is very similar to that observed for anatase nanoparticles. Three cationic redox systems, Meldola’s blue, Ni 2+, and cytochrome c, are immobilised on the TiO 2 nanotube surface; the binding ability and the number of binding sites are quantified voltammetrically. Redox proteins, such as cytochrome c, adsorb readily and irreversibly. Well-defined voltammetric signals for the immobilised protein are observed in an aqueous buffer. TiO 2 nanotubes are shown to be novel, inert substrates for both inorganic and biological electrocatalysts.