The ability to detect and positively identify molecules under extremely dilute conditions is important for the health of both humankind and the environment. At present, few measurement science techniques can robustly approach the measurement of just a few thousand molecules. Here, we present an electrochemical platform for the detection and positive identification of fewer than 1,000 molecules of decamethylferrocene ((Cp*)2FeII). We achieve this remarkable detection threshold by trapping (Cp*)2FeII in a 1,2-dichloroethane microdroplet, which is allowed to dissolve into an aqueous continuous phase while on a gold microelectrode (radius~6.25 m). Because electrochemistry is not sensitive enough to observe the charge of less than 1,000 molecules, we dissolved M amounts hexacyanoferrate (III) in the aqueous continuous phase. The biphasic reaction between hexacyanoferrate (III) and Cp2*(Fe)II allows for a feedback loop when the microelectrode is biased sufficiently negative to reduce Cp2*(Fe)III. This feedback loop, a typical EC’ catalytic mechanism, amplifies the electrochemical signal of Cp2*(Fe)II when the droplet is of small enough dimensions for feedback to occur. Our results demonstrate that clever biphasic reactions can be coupled with dissolving droplets to access extremely low limits of quantitation in electroanalysis.

中文翻译：

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放大溶解微滴中 < 1000 个分子的电化学足迹

在极其稀薄的条件下检测和积极识别分子的能力对于人类和环境的健康都很重要。目前，很少有测量科学技术能够可靠地测量几千个分子。在这里，我们提出了一个电化学平台，用于检测和阳性鉴定少于 1,000 个十甲基二茂铁 ((Cp*)2FeII) 分子。我们通过将 (Cp*)2FeII 捕获在 1,2-二氯乙烷微滴中实现了这一显着的检测阈值，该微滴在金微电极（半径~6.25 µm）上溶解到水连续相中。由于电化学不够灵敏，无法观察少于 1,000 个分子的电荷，因此我们在水连续相中溶解了 M 量的六氰基铁酸盐 (III)。当微电极偏置足够负以还原 Cp2*(Fe)III 时，六氰基铁酸盐 (III) 和 Cp2*(Fe)II 之间的双相反应可形成反馈回路。这种反馈回路是一种典型的 EC 催化机制，当液滴尺寸足够小以发生反馈时，它会放大 Cp2*(Fe)II 的电化学信号。我们的结果表明，巧妙的双相反应可以与溶解液滴相结合，以达到电分析中极低的定量限。