In this work, we report the electrochemical response of a boron-doped ultrananocrystalline diamond (BDUNCD) microelectrode during long-term dopamine (DA) detection. Specifically, changes to its electrochemical activity and electroactive area due to DA byproducts and surface oxidation are studied via scanning electron microscopy, energy dispersive spectroscopy, electrochemical impedance spectroscopy, and silver deposition imaging (SDI). The fouling studies with amperometry (AM) and fast scan cyclic voltammetry (FSCV) methods suggest that the microelectrodes are heavily fouled due to poor DA-dopamine- o-quinone cyclization rates followed by a combination of polymer formation and major changes in their surface chemistry. SDI data confirms the presence of the insulating polymer with sparsely distributed tiny electroactive regions. This resulted in severely distorted DA signals and a 90% loss in signal starting as early as 3 h for AM and a 56% loss at 6.5 h for FSCV. This underscores the need for cleaning of the fouled microelectrodes if they have to be used long-term. Out of the three in vivo suitable electrochemical cycling cleaning waveforms investigated, the standard waveform (-0.4 V to +1.0 V) provides the best cleaned surface with a fully retained voltammogram shape, no hysteresis, no DA signal loss (a 90 ± 0.72 nA increase), and the smallest charge transfer resistance value of 0.4 ± 0.02 MΩ even after 6.5 h of monitoring. Most importantly, this is the same waveform that is widely used for in vivo detection with carbon fiber microelectrodes. Future work to test these microelectrodes for more than 24 h of DA detection is anticipated.

中文翻译：

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多巴胺检测过程中超纳米晶金刚石微电极的表面结垢：通过电化学循环改善寿命。

在这项工作中，我们报告了在长期多巴胺（DA）检测期间掺硼的超纳米晶金刚石（BDUNCD）微电极的电化学响应。具体而言，通过扫描电子显微镜，能量分散光谱，电化学阻抗光谱和银沉积成像（SDI）研究了由于DA副产物和表面氧化引起的电化学活性和电活性面积的变化。使用安培法（AM）和快速扫描循环伏安法（FSCV）方法进行的结垢研究表明，由于DA-多巴胺-邻醌的环化率低，随后形成聚合物，表面化学性质发生重大变化，微电极严重结垢。SDI数据证实了存在稀疏分布的微小电活性区域的绝缘聚合物。这导致DA信号严重失真，AM最早3小时开始的信号损失为90％，而FSCV 6.5小时开始的信号损失为56％。这强调了如果必须长期使用污垢的微电极，则需要对其进行清洁。在研究的三种体内合适的电化学循环清洁波形中，标准波形（-0.4 V至+1.0 V）提供了最佳的清洁表面，具有完全保留的伏安图形状，无滞后，无DA信号损失（90±0.72 nA）即使在监测6.5小时后，最小的电荷转移电阻值也为0.4±0.02MΩ。最重要的是，这是与碳纤维微电极在体内检测中广泛使用的相同波形。预期将来会测试这些微电极进行超过24小时的DA检测。