Electrochemical Conversion of Unreactive Pyrene to Highly Redox-Active 1,2-Quinone Derivatives on a Carbon Nanotube-Modified Gold Electrode Surface and Its Selective Hydrogen Peroxide Sensing

Pyrene (PYR) is a rigid, carcinogenic, unreactive, and non-electrooxidizable compound. A multiwalled carbon nanotube (MWCNT)-modified gold electrode surface-bound electrochemical oxidation of PYR to a highly redox-active surface-confined quinone derivative (PYRO) at an applied potential of 1 V versus Ag/AgCl in pH 7 phosphate buffer solution has been demonstrated in this work. Among various carbon nanomaterials examined, the pristine MWCNT-modified gold electrode showed effective electrochemical oxidation of the PYR. The MWCNT's graphite impurity promotes the electrochemical oxidation reaction. Physicochemical and electrochemical characterizations of MWCNT@PYRO by Raman spectroscopy, FT-IR, X-ray photoelectron spectroscopy, and GC-MS reveal the presence of PYRO as pyrene-tetrone within the modified electrode. The quinone position of PYRO was identified as ortho-directing by an elegantly designed ortho-isomer-selective complexation reaction with copper ion as an MWCNT@PYRO-Cu2+/1+-modified electrode. Finally, a cytochrome c enzyme-modified Au/MWCNT@PYRO (i.e., Au/MWCNT@PYRO-Cyt c) was also developed and further demonstrated for the selective biosensing of hydrogen peroxide.