A novel amperometric biosensor for the detection of nitrophenol

Abstract

We report on a novel amperometric biosensor for detecting phenolic compounds based on the co-immobilization of horseradish-peroxidase (HRP) and methylene blue (MB) with chitosan on Au-modified TiO 2 nanotube arrays. The titania nanotube arrays were directly grown on a Ti substrate using anodic oxidation first; a gold thin film was then coated onto the TiO 2 nanotubes by an argon plasma technique. The morphology and composition of the fabricated Au-modified TiO 2 nanotube arrays were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Cyclic voltammetry and amperometry were used to study the proposed electrochemical biosensor. The effect of pH, applied electrode potential and the concentration of H 2O 2 on the sensitivity of the biosensor have been systemically investigated. The performance of the proposed biosensor was tested using seven different phenolic compounds, showing very high sensitivity; in particular, the linearity of the biosensor for the detection of 3-nitrophenol was observed from 3 × 10 −7 to 1.2 × 10 −4 M with a detection limit of 9 × 10 −8 M (based on the S/N = 3).