聚苯并咪唑-漆酶复合物修饰电极无电子传递媒介体催化氧还原性能

Catalysis of Poly Benzimidazole and Laccase Composite Modified Electrode for Oxygen Reduction Reaction Without Electron Transfer Mediators

采用循环伏安法将聚苯并咪唑和漆酶的复合物共沉积在玻碳电极表面。制备的漆酶基电极在O2气饱和的磷酸盐缓冲液中可以观察到明显的催化还原电流,实现了无媒介体的酶-电极间直接电子迁移,电极静止时氧还原起始电位为645 mV,近于漆酶活性位T1的式电位580 mV,而极限扩散催化电流密度可达318.5×10-6A/cm2。但由于O2气在致密的固酶导电聚合物修饰层中扩散不够快(扩散系数只有在溶液中的1.25%),导致电极以较高速度旋转时极限扩散催化电流密度仅仅增加到1×10-3A/cm2。根据静态时极限催化电流密度求算得到的固定漆酶催化氧还原平均转化率为21.7/s。这种漆酶基电极具有良好的重现性和长期使用性(储存10 d后催化活力仍然保持了初始值的80%以上),在人体生理温度和弱酸性条件下具有最佳催化活力。这种漆酶基电极作为氧传感器具有良好的传感性能:检测限低(0.5μmol/L),灵敏度高(71.1μA.L/mmol),且对O2具有良好的亲和力(KM=89.9μmol/L)。

Poly benzimidazole and laccase were co-deposited on the surface of glassy carbon electrode by cyclic voltammetry method.Apparent catalytic reduction current was observed when the as-prepared laccase based electrode was immersed in oxygen-saturated phosphate buffer solution,indicating the viability of direct electron transfer between electrode and immobilized enzyme without external mediator existence.The result showed the onset potential of oxygen reduction reaction（ORR） was 645 mV,in the vicinity of the formal potential corresponding to T1 copper site in laccase（580 mV）,while the limited diffusion catalytic current density could be up to 318.5×10-6 A/cm2.The slow diffusion in the dense-packed conductive polymer thin film layer on the surface of electrode（the diffusion coefficient is only 1.25% of measured value in solution） resulted in a slight enhancement in limited diffusion catalytic current density：-1×10-3 A/cm2 at the relatively high rotating speed.The average turn-over frequency of catalytic oxygen reduction induced by entrapped laccase was evaluated to be 21.7/s according to the stationary limit catalytic current density.This laccase based electrode displayed favorable reproducibility and long-term usability（catalytic activity could retain ca.80% of its initial value after a storage for 10 days）.This biocathode had superior activity at physiological temperature of human being and under weak acidic conditions,and demonstrated excellent sensor function for oxygen molecules： low detection limit（0.5 μmol/L）,high sensitivity（71.1 μA·L/mmol） and favorable affinity（KM=89.9 μmol/L）.