Direct electrochemistry of horseradish peroxidase on TiO(2) nanotube arrays via seeded-growth synthesis

Horseradish peroxidase (HRP) was successfully immobilized on vertically oriented TiO 2 nanotube arrays (NTAs), which was prepared by a seeded-growth mechanism. The nanotubular structure of TiO 2 was characterized by scanning electron microscope (SEM). After encapsulated HRP on TiO 2 nanotube arrays, the direct electron transfer of HRP was observed. Owing to the redox reaction of electroactive center of HRP, the HRP/TiO 2 NTAs modified electrode exhibited a pair of quasi-reversible peaks with the peak-to-peak separation of 70 mV and the formal potential of −0.122 V (vs. SCE) in 0.2 mol L −1 phosphate buffer solution (PBS, pH 7.0). The number of transference electron was 0.84 and the direct electron transfer (ET) constant ( k s ) was 3.82 s −1 . The HRP/TiO 2 NTAs modified electrode displayed an excellent electrocatalytic performance for H 2 O 2 and the formal Michaelis–Menten constant ( K m app ) was 1.9 mmol L −1 . The response currents had a good linear relation with the concentration of H 2 O 2 from 5.0 × 10 −7 mol L −1 to 1.0 × 10 −5 mol L −1 and 5.0 × 10 −5 mol L −1 to 1.0 × 10 −3 mol L −1 , respectively.