Zhu Feng, Yan Jiawei, Pang Shiwei, Zhou Yongliang, Mao Bingwei, Oleinick Alexander, Svir Irina, Amatore Christian
State Key Laboratory for Physical Chemistry of Solid Surfaces, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University , Xiamen, Fujian 361005, People's Republic of China.
Anal Chem. 2014 Mar 18;86(6):3138-45. doi: 10.1021/ac404202p. Epub 2014 Feb 24.
Recessed microelectrode arrays and plane-recessed microelectrode arrays (MEAs) with different center-to-center distances are designed and fabricated using lithographic technology. By comparing electrochemical behavior of plane-recessed MEAs with that of recessed MEAs, bipolar phenomenon of the metallic plane film is revealed. Redox cycling can occur when the top plane electrode was floating; that is, the bipolar behavior of the unbiased top plane electrode may perform locally as a collector and enlarge the concentration gradient of Ru(NH3)6Cl3 and thus promote an apparent generator/collector electrochemical response of the microdisk electrode in the MEAs configuration. By utilizing the bipolar behavior, the center-to-center distance of MEAs required for achieving steady-state current could decrease without favoring at the same time the overlapping of diffusion layers of microelectrodes, and thus, the electrode density of MEAs can be increased. Therefore, the bipolar behavior of the metallic film can increase both the current response of an individual microdisk and the electrode density of microdisks without losing the characteristics of a microelectrode. By just fabricating a thin layer of metallic film on the plane and leaving it floating without potential control, recessed MEAs used in this work can achieve the increase of detection sensitivity by more than 1 order of magnitude.
采用光刻技术设计并制作了具有不同中心距的嵌入式微电极阵列和平凹式微电极阵列（MEA）。通过比较平凹式MEA和嵌入式MEA的电化学行为，揭示了金属平面薄膜的双极现象。当顶部平面电极处于浮动状态时会发生氧化还原循环；也就是说，无偏置顶部平面电极的双极行为可能会局部充当集电极，增大Ru(NH₃)₆Cl₃的浓度梯度，从而促进MEA配置中微盘电极明显的发生器/集电极电化学响应。通过利用双极行为，实现稳态电流所需的MEA中心距可以减小，同时又不会有利于微电极扩散层的重叠，因此，可以提高MEA的电极密度。所以，金属薄膜的双极行为可以增加单个微盘的电流响应以及微盘的电极密度，而不会丧失微电极的特性。通过仅在平面上制作一层金属薄膜并使其在无电位控制的情况下处于浮动状态，本工作中使用的嵌入式MEA可实现检测灵敏度提高超过1个数量级。
