Preparation Of Graphene-porphyrin Composite Electrode And Its Electrocatalytic Properties

Recently, with the discovery of novel carbon nanomaterials, graphene attractedspecial interest in the scientific community. Graphene is a new type of2D materials,possessing properties such as very thin, high electeical conductivity, significantmechanicai strength, chemical stability and larger surface area. As a consequence,graphene can serve as an excellent substrate for the development of biosensors devicesor as a modified material to promote electron transfer between biological moleculeswith electrode.Metallo-porphrins,as the mimics of many important enzymes, have been widelyapplied as electro media for the research of electrochemical catalysis. EspeciallyMn-porphyrins, as a catalyst, its life cycle is longer than others Metallo-porphrin, sothe Mn-porphyrins have been the hot area of research on the optical and electricalcatalytic.Porphyrin-Graphene composite can well combine the advantages of both, the effectof electron-transfer between them can improve the photoelectric properties ofcomplexes. Now, the preparation methods of grapheme-porphyrin complexes arecovalent bonding and non-covalent bonding, because the non-covalent complexes areinstability, so we chose a covalent bonding way to achieve porphyrin functionalizedgraphene. We found the complexes has good optical properties, moreover, its electriccatalytic activity is satisfactory.In this paper, a chloro [5-(4-Aminophenyl)-10,15-20-triphenylporphyrin] Mn(III)and graphene oxide molecules are covalently bonded together by an amide bond, thenmodified it on glassy carbon electrode surface and used for the electrocatalyticoxidation of AA and nitrite. MnTPP-NHCO-Graphene composites were characterizedby UV–vis, FT-IR and TEM, the results revealed that the MnTPP molecules have beencovalently bonded to the graphene by an amide linkage. Compared with non-covalentporphyrin functionalized graphene, the covalent complex has higher stability, it cansignificantly increase the stability and improve the electrochemical performance ofelectrochemical sensor. Between the oxidation peak current and the AA or NO2-concentration was obtained by Cyclic Voltammetry (CV), the rusults showed theoxidation peak current for AA and nitrite at the MnTPP-NHCO-Graphene/GC electrodeincreased significantly compared with that at the bare GCE, moreover, a large negativeshift in the oxidation potentials of AA and nitrite indicating that MnTPP-NHCO-Graphene has a quite good catalytic activity for oxidation, the relationshipbetween the oxidation peak current and the AA(NO2-) concentration was with a linearrange of0.2~2mM (1mM~10mM). In order to get a lower limit of detection, we alsoused differential pulse Voltammetry (DPV) method for analyzing the detection of AA, the results showed the relationship between the oxidation peak current and the AAconcentration was with a linear range of0.04~0.28mM. These indicated that themodified electrodes have enormous potential for detection of AA and NO2-. In addition,The modified electrode has a good sensitivity,stability and repatability.