Hydrogen peroxide detection at a horseradish peroxidase biosensor with a Au nanoparticle–dotted titanate nanotube|hydrophobic ionic liquid scaffold

In this work, a novel sensing scaffold, consisting Au nanoparticle (GNP)–dotted TiO2 nanotubes (TNTs) as the rigid material and the hydrophobic ionic liquid (HIL), 1-decyl-3-methylimidazolium tetrafluoroborate, as the entrapping agent, was applied to facilitate the electron transfer of horseradish peroxidase (HRP) on a glassy carbon electrode. GNPs were immobilised on the TNTs in our work using a one-step reduction of HAuCl4·3H2O by sodium borohydride in the presence of sodium citrate as a stabilising reagent. The morphology and composition of the as-synthesised composite materials were characterised by transmission electron microscopy, scanning electron microscopy, X-ray diffraction and Fourier-transform infrared spectroscopy. Cyclic voltammetry of HRP at the modified electrode presented a pair of reproducible, quasi-reversible redox peaks with a peak-to-peak separation of 69 mV, indicating electron transfer between HRP and composite electrode. The GNP–TNT|HIL|HRP electrode was then applied to the detection of H2O2 in a pH 7.0 phosphate buffer using chronoamperometry. The biosensor exhibited a linear response in the 15–750 μM range, and a limit of detection of 2.2 μM. The biosensor also exhibited stability with 90% of the detection signal retained over a two-week duration.

► Au nanoparticle-modified TiO2 nanotubes prepared by a one step reduction of HAuCl4·3H2O.
► Composite material consisting of Au nanoparticle-modified TiO2 nanotubes and hydrophobic ionic liquid facilitated electron transfer of horseradish peroxidase.
► Immersion of composite material in water before drying aided in rapid gelation of ionic liquid.
► Detection limit down to 2.2 μM hydrogen peroxide achieved at composite material entrapped with horseradish peroxidase.