Abstract
Hydrogen peroxide is an important analyte both from the standpoints of in vivo and in vitro analyses. Electrochemical methods offer good prospects, but present sensing methods suffer from inadequate limits of detection (LOD), low sensitivity, poor stability, and numerous interferents. To address these issues, we use the recently recognized peroxidase-like activity of ferrocene for sensing based on the reductive electrocatalysis of H2O2. This route obviates interferences from ascorbate, urea, urate, dopamine and glucose. Immobilization of ferrocene overcomes its low aqueous solubility. This is done by the chemical modification of a pseudo-graphite material rich in sp3 defects. The surface is modified for carboxylate features through a diazonium intermediate formed through 4-aminobenzoic acid. Aminoferrocene is attached to surface carboxylate groups through a N-ethyl-N′-(3-(dimethylamino)propyl) carbodiimide coupling agent. Cyclic voltametric studies indicate that the surface concentration of ferrocene is 1.06 x10-9 mol/cm2. Chronoamperometric response at -0.6 V vs. Ag/AgCl, gives a LOD of 0.070 µM with a high sensitivity 553.2 μA*mM-1*cm-2. This is the best sensitivity reported in literature. Furthermore, the sensor is stable over 50 cyclic voltametric scans, and between the 3 calibration curve studies.