Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States.
Lineberger Comprehensive Cancer Center, School of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States.
Anal Chem. 2020 Dec 15;92(24):16260-16266. doi: 10.1021/acs.analchem.0c04183. Epub 2020 Nov 26.
We report a technique to amplify the electrochemical signal within micro- and nanodroplets radical annihilation amplification. Toluene droplets filled with decamethylferrocene (DmFc) are suspended in an aqueous solution containing 10 mM NaClO and 10 μM NaCO. When a toluene droplet irreversibly collides with an ultramicroelectrode biased sufficiently positive for concurrent oxidation of DmFc and oxalate (CO), blip-type responses are observed in the amperometric -t trace even when the concentration of DmFc is 50 nM. The toluene droplet wetting the ultramicroelectrode effectively creates a microgap, where DmFc molecules are oxidized to DmFc. In the continuous phase, the oxidation of oxalate (CO) produces a strong reducing agent, CO. Regeneration of DmFc radical annihilation amplifies the current, similar to conventional nanogap experiments. This experiment allows one to observe the electrochemistry of hundreds to thousands of molecules trapped in a femtoliter droplet, enhancing the sensitivity of droplet-based electrochemistry by 5 orders of magnitude. Finite element simulations validate our experimental results and indicate the importance of the droplet geometry to amplification.
我们报告了一种在微纳米液滴中放大电化学信号的技术——自由基湮灭放大。甲苯液滴中充满了十甲基二茂铁（DmFc），悬浮在含有 10 mM NaClO 和 10 μM NaCO 的水溶液中。当甲苯液滴不可逆地与一个偏置足够正的超微电极碰撞，同时氧化 DmFc 和草酸盐（CO）时，即使 DmFc 的浓度为 50 nM，在安培计时 -t 轨迹中也会观察到 blip 型响应。超微电极润湿的甲苯液滴有效地形成了一个微间隙，其中 DmFc 分子被氧化为 DmFc。在连续相中，草酸盐（CO）的氧化产生了一种强还原剂 CO。DmFc 自由基的再生放大了电流，类似于传统的纳米间隙实验。该实验允许人们观察到被困在皮升液滴中的数百到数千个分子的电化学行为，将基于液滴的电化学灵敏度提高了 5 个数量级。有限元模拟验证了我们的实验结果，并表明液滴几何形状对放大的重要性。
