Porous Graphitized Carbon Monolith as an Electrode Material for Probing Direct Bioelectrochemistry and Selective Detection of Hydrogen Peroxide

For the first time, graphitized carbon particles with a high surface area have been prepared and evaluated as a new material for probing direct electrochemistry of hemoglobin (Hb). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) imaging revealed that the carbon monolithic skeleton was constructed by a series of mesopores with irregular shapes and an average pore diameter of similar to 5.6 nm. With a surface area of 239.6 m(2)/g, carbon particles exhibited three major Raman peaks as commonly observed for carbon nanotubes and other carbon materials, i.e., the sp(3) and sp(2) carbon phases coexisted in the sample. A glassy carbon electrode modified with carbon monoliths and didodecyldimethylammonium bromide exhibited direct electron transfer between Hb molecules and the underlying electrode with a transfer rate constant of 6.87 s(-1). The enzyme electrode displayed a pair of quasi-reversible reduction oxidation peaks at -0.128 and -0.180 V, reflecting the well-known feature of the heme [Fe3+/Fe2+] redox couple: a surface-controlled electrochemical process with one electron transfer. This reagentless biosensing approach was capable of detecting H2O2, a simple molecule but plays an important role in analytical and biological chemistry, as low as 0.1 mu M with linearity of 0.1-60 mu M and a response time of <0.8 s, comparing favorably with other carbon based electrodes (5 s).