三维金纳米团簇/多壁碳纳米管-Nafion膜修饰电极的电化学制备及血红蛋白的直接电化学

Electrodeposition of Gold Nanoparticle Clusters on Multi-Wall Carbon Nanotubes and the Direct Electrochemistry of Hemoglobin

用改进的全电化学三步法制备三维金纳米团簇/多壁碳纳米管(3D Au/MWCNTs)纳米复合材料,并用Nafion(Nafion)膜进行涂布固定,制得3D Au/MWCNTs-Nafion修饰电极.利用透射电子显微镜(TEM)和能量色散光谱(EDS)对所得纳米复合材料的形貌进行表征.3D Au/MWCNTs具有金纳米核团簇而成的特殊圆丘状三维结构,电化学活性表面积(ECSA)比均匀分散的Au/MWCNTs提高了一个数量级,可有效提高血红蛋白(Hb)在电极表面的负载量.运用循环伏安法和计时电流法对3D Au/MWCNTs-Nafion修饰电极的生物电催化性质进行研究,其在Hb溶液中显示了良好的电催化活性和稳定性:还原氧化峰电流高,反应可逆性好,提供了有利于Hb直接电子转移的电化学环境.固载于Au/MWCNTs-Nafion上的Hb能够保持其生物活性,对双氧水(H2O2)表现出良好的催化性能,这是3D Au纳米团簇和MWCNTs共同作用的结果.实验表明,3D Au/MWCNTs-Nafion修饰电极结构特殊、性能优越,对Hb的直接电化学研究具有积极的促进作用,为准确高效的检测Hb及相关生物活性物质提供了新的电极选择.

Three-dimensional structure gold nanoparticle clusters（3D Au） were electrodeposited onto multiwalled carbon nanotubes（MWCNTs） through improved three-step method,which involves：（1） potential cycling（CV,200 mV s-1） from ＋1.8 to-0.4 V was performed in 0.5 mol/L K2SO4 solutions for 10 min in order to produce oxide functional groups（carbonyl,hydroxyl,and carboxyl） at the defect sites located at the ends and/or the sidewalls of MWCNTs,（2） electrochemical oxidation of the Au（Ⅲ） complex to the Au（V） complex from 2 mol/L K2PtCl4＋0.1 mol/L K2SO4aqueous solutions by using potential-step method（PS）.The potential was jumped from 0.3 V to 1.1 V with different pulse width and this was repeated until a steady pulse current was reached.and（3） electrochemical transformation of the Au（V） complex to Au nanoparticle clusters on the surface of MWCNTs through cycling from ＋1.0 to-0.26 V in 0.1 mol/L H2SO4 solutions to the steady state.For comparison,however,experiments were also carried out with CV in the second step（2 mol/L K2PtCl4＋0.1 mol/L K2SO4 aqueous solution with 190 cycles： these proved to be the optimal conditions）.The morphology of 3D Au/MWCNTs electrode was characterized by transmission electron microscopy（TEM） and energy dispersive X-ray spectroscopy（EDS）.The voltammetric behavior of hemoglobin（Hb） on 3D Au/MWCNTs-Nafion has been investigated in 10 nmol/L Hb solution（pH=6 PBS） by cyclic voltammetry（CV） and current-time method（CT）.Compared with Au＋MWCNTs-Nafion（＋means mix together）,Au/MWCNTs-Nafion（uniform Au nanoparticle dispersion of MWCNTs,which was obtained when the second step adopts cyclic voltammetry instead of potential-step method）,3D Au/MWCNTs-Nafion gave a higher peak current and better reversibility.The higher sensitivity and lower detection limit show that 3D Au/MWCNTs-Nafion can offer a conductive microenvironment for the immobilized Hb to achieve direct electrochemistry.The average coverage（Γ） of Hb immobilized on 3D Au/MWCNTs-Nafion was calculated to be 7.65×10 9mol cm 2,testifies a high surface-to-volume ratio.Electron transfer rate constant（kS） was calculated to be 1.8 s-1,which was proved 3D Au/MWCNTs-Nafion is more conducive to direct electron transfer between Hb and the electrode.Hb/Au/MWCNTs-Nafion potential application towards the electrocatalytic reduction of H2O2was also conducted to show immobilized Hb exhibits excellent biocompatibility and stability.Our work points to a new path for the preparation of 3D Au/MWCNTs nanocomposites,which are promising as electrocatalysts in direct electrochemistry of Hb.