Direct Electrochemical Tyrosinase Biosensor based on Mesoporous Carbon and Co3O4 Nanorods for the Rapid Detection of Phenolic Pollutants

A novel tyrosinase (Tyr) biosensor based on a graphitized ordered mesoporous carbon/cobaltosic oxide nanorod (GMC/ Co3O4) nanocomposite is developed for the rapid detection of phenolic pollutants. By applying the GMC/Co3O4 nanocomposite as an enzyme immobilization matrix, rapid direct electron transfer between Tyr and the electrode is achieved. The biosensor exhibits a wide linear response for catechol, ranging from 5.0 x 10(-8) to 1.3 x 10(-5) m, with a limit of detection down to 25 nm and a response time of less than 2 s. The sensitivity of the biosensor based on the GMC/Co3O4 nanocomposite (6.4 AM(-1)cm(-2)) is higher than that of the biosensor based on GMC (5.0 AM(-1)cm(-2)) or Co3O4 (3.5 AM-1cm(-2)), which can be attributed to the synergistic effect of the GMC/Co3O4 nano- composite. The biosensor is further used to systematically detect mixed phenolic samples (phenol, catechol, m- cresol, p- cresol, and 4- chlorophenol) and real water samples. The biosensor- based detection results for river water and tap water samples show outstanding average recovery (92.2- 103.3%) and relative standard deviations (0.9- 7.8 %). In comparison with the conventional spectrophotometric method, the biosensor method is more rapid, sensitive, accurate, and convenient. Furthermore, the detection limit of the biosensor method is about 20 times lower than that of the spectrophotometric method. This novel biosensor is proven to be a promising alternative tool for the rapid and on- site monitoring of environmental phenolic pollutants.