Direct Electrochemistry and Catalytic Function on Oxygen Reduction Reaction of Electrodes Based on Two Kinds of Magnetic Nano-particles with Immobilized Laccase Molecules

Synthesized carboxymethylated Chitosan coupled magnetic Fe3O4 nano-particles and phthaloyl Chitosan overlapped magnetic Fe3O4 nano-particles, were used as enzyme matrices to prepare two prototypes of Laccase-based electrodes. Dependences of structural and operating parameters on characteristics of spectrometry, aggregation status and catalysis for oxygen reduction reaction of surface anchored protein molecules, were investigated and compared by electrochemical means in combination with spectroscopy and transmission electron microscopy. Results from experiments revealed that the latter electrode displayed favorable catalytic effect in oxygen reduction reaction in the absence of mediator. Key factor in limiting the efficiency of catalysis was ascribed to the diffusion process of the substrate into the layer of nano-particles containing Laccase. While the former electrode only showed efficient catalytic effect in oxygen reduction reaction in the presence of electron mediator with rate determining step in mass-transferring of mediator.