Interdepartmental Program in Biomolecular Science and Engineering, University of California at Santa Barbara, Santa Barbara, California 93106, United States.
Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, California 93106, United States.
J Am Chem Soc. 2021 Nov 17;143(45):18888-18898. doi: 10.1021/jacs.1c04971. Epub 2021 Nov 4.
Blocking electrochemistry, a subfield of nanochemistry, enables nondestructive, measurement of the concentration, size, and size heterogeneity of highly dilute, nanometer-scale materials. This approach, in which the adsorptive impact of individual particles on a microelectrode prevents charge exchange with a freely diffusing electroactive redox mediator, has expanded the scope of electrochemistry to the study of redox-inert materials. A limitation, however, remains: inhomogeneous current fluxes associated with enhanced mass transfer occurring at the edges of planar microelectrodes confound the relationship between the size of the impacting particle and the signal it generates. These "edge effects" lead to the overestimation of size heterogeneity and, thus, poor sample characterization. In response, we demonstrate here the ability of catalytic current amplification (EC') to reduce this problem, an effect we term "electrocatalytic interruption". Specifically, we show that the increase in mass transport produced by a coupled chemical reaction significantly mitigates edge effects, returning estimated particle size distributions much closer to those observed using electron microscopy. In parallel, electrocatalytic interruption enhances the signal observed from individual particles, enabling the detection of particles significantly smaller than is possible via conventional blocking electrochemistry. Finite element simulations indicate that the rapid chemical kinetics created by this approach contributes to the amplification of the electronic signal to restore analytical precision and reliably detect and characterize the heterogeneity of nanoscale electro-inactive materials.
阻断电化学是纳米化学的一个分支，它能够实现对高度稀释的纳米级材料的浓度、尺寸和尺寸异质性的无损、测量。这种方法中，单个颗粒对微电极的吸附作用阻止了与自由扩散的电化学活性氧化还原介质的电荷交换，从而将电化学扩展到了对氧化还原惰性材料的研究。然而，仍然存在一个限制：在平面微电极边缘发生的增强传质引起的不均匀电流通量，混淆了撞击颗粒的尺寸与其产生的信号之间的关系。这些“边缘效应”导致尺寸异质性的高估，从而导致样品特征描述不佳。作为回应，我们在这里展示了催化电流放大 (EC') 减少这个问题的能力，我们将这种效应称为“电催化中断”。具体来说，我们表明，耦合化学反应产生的质量传输增加显著减轻了边缘效应，使估计的颗粒尺寸分布更接近使用电子显微镜观察到的结果。同时，电催化中断增强了从单个颗粒观察到的信号，使得能够检测到比传统阻断电化学小得多的颗粒。有限元模拟表明，这种方法所产生的快速化学反应动力学有助于放大电子信号，以恢复分析精度，并可靠地检测和表征纳米级电惰性材料的异质性。
