Polydopamine-assisted decoration of TiO2 nanotube arrays with enzyme to construct a novel photoelectrochemical sensing platform

A novel photoelectrochemical (PEC) biosensing platform coupling with enzyme-induced biocatalytic precipitation (BCP) for H 2 O 2 was successfully constructed. TiO 2 nanotube arrays (TNs) were coated with polydopamine (PDA) and horseradish peroxidase (HRP) as the PEC electrode through a facile method. PDA was incorporated into the sensor system not only as a sensitizing agent to alter the optical properties of TiO 2 nanotube arrays and enhance the visible light (λ   >   400   nm) absorption, but also as a bonding resin to HRP via Michael addition or Schiff base reaction. The immobilized HRP on the PEC electrodes could induce BCP reaction as the signal amplifier by oxidizing the 4-chloro-1-naphthol (4-CN) into insoluble products in the presence of H 2 O 2 . The quantitative monitoring of H 2 O 2 could be realized thanks to the photocurrent decrease caused by the BCP generated insoluble products deposited on the PEC electrode surface. The fabricated TNs@HRP/PDA PEC electrode for biosensing of H 2 O 2 exhibited a good sensitivity as well as selectivity in a detection range from 1   nM to 50   μM, with a detection limit of 0.7   nM.