期刊
ACS NANO
卷 10, 期 3, 页码 3658-3664出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.6b00049
关键词
redox cycling nanopore electrode array; ion accumulation; ion migration; current amplification; electrical double layer effect
类别
资金
- National Science Foundation [1404744]
- Department of Energy Office of Science [DE FG02 07ER15851]
- Direct For Mathematical & Physical Scien
- Division Of Chemistry [1404744] Funding Source: National Science Foundation
Ion permselectivity can lead to accumulation in zero-dimensional nanopores, producing a significant increase in ion concentration, an effect which may be combined with unscreened ion migration to improve sensitivity in electrochemical measurements, as demonstrated by the enormous current amplification (2000-fold) previously observed in nanopore electrode arrays (NEA) in the absence of supporting electrolyte. Ionic strength is a key experimental factor that governs the magnitude of the additional current amplification (AF(ad)) beyond simple redox cycling through both ion accumulation and ion migration effects. Separate contributions from ion accumulation and ion migration to the overall AFad were identified by studying NEAs with varying geometries, with larger AFad values being achieved in NEAs with smaller pores. In addition, larger AFad values were observed for Ru(NH3)(6)(3/2+) than for ferrocenium/ferrocene (Fc+/Fc) in aqueous solution, indicating that coupling efficiency in redox cycling can significantly affect AFad. While charged species are required to observe migration effects or ion accumulation, poising the top electrode at an oxidizing potential converts neutral species to cations, which can then exhibit current amplification similar to starting with the cation. The electrical double layer effect was also demonstrated for Fc/Fc+ in acetonitrile and 1,2-dichloroethane, producing AFad up to 100x at low ionic strength. The pronounced AFad effects demonstrate the advantage of coupling redox cycling with ion accumulation and migration effects for ultrasensitive electrochemical measurements.
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