Tyrosinase was immobilized on multiwalled carbon nanotube (MWNT) supports that were functionalized with multiple groups. It was then used for the detection of phenolic compounds. The radiation-induced graft polymerization of 1-[(4-ethenylphenyl)methyl]-3-buthyl-imidazolium chloride and vinyl ferrocene introduced functional groups derived from both species onto the nanotubes' surfaces: imidazolium salts that contained sites for the enzyme's immobilization via ionic bonding and ferrocene compounds that acted as electron transfer mediators via redox reactions. Using these additives at a 1 : 4 molar ratio resulted in an electrode with optimized current. The multifunctionalized nanotube supports were characterized by X-ray photoelectron spectroscopy, transmission electron microscopy, and thermogravimetric analysis. The prepared tyrosinase-immobilized biosensor showed a sensing range of 1.0 x 104 M to 7.0 x 104 M and was used for the detection of phenolic compounds in red wines. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013