Electrochemical sensing platform based on covalent immobilization of thionine onto gold electrode surface via diazotization-coupling reaction

A novel electrochemical sensing platform by modification of electroactive thionine (Th) onto gold electrode surface was constructed which was realized by diazotization of 4-aminothiophenol (ATP) self-assembled monolayer followed by coupling of Th with the diazonium group to form a covalent diazo bond A pair of well-defined redox peaks of Th was observed in the cyclic voltammetric measurement The resulting diazo-ATP monolayer displayed superior electrical conductivity which contributed to I he sensitive detection of hydrogen peroxide (H(2)O(2)) The immobilized Th also showed a remarkable stability which may benefit from the pi-pi stacking force and the covalent diazo bond between diazo-ATP and Th molecules Under the optimized experimental conditions the current fabricated non-enzyme and reagentless sensor could show a rapid response to H(2)O(2) within 3s and a linear calibration plot ranged from 1 0 x 10(-6) to 638 x 10(-3) M with a detection limit of 67 x 10(-7) M The current fabrication strategy of electroactive interface is expected to be used as a versatile route for the immobilization of more electroactive molecules and offer more opportunities for the applications in electrochemical sew or biosensor electrocatalysis etc (C) 2010 Elsevier 8 V All rights reserved