Single-molecule (SM) detection is essential for investigating processes at the molecular level. Nanogap-based detection approaches have proven to be highly accurate SM capture and detection platforms in the last decade. Unfortunately, these approaches face several inherent drawbacks, such as short detection times and the effects of Brownian motion, that can hinder molecular capture. Nanogap-based SM detection approaches have been successfully coupled to optical-based setups to exploit nearfield-assisted trapping to overcome these drawbacks and thus improve SM capture and detection. Here we present the first mechanistic study of nearfield effects on SM capture and release in nanogaps, using unsupervised machine learning methods based on hidden Markov models. We show that the nearfield strength can manipulate the kinetics of the SM capture and release processes. With increasing field strength, the rate constant of the capture kinetics increase while the release kinetics decrease, favouring the former over the latter. As a result, the SM capture state is more likely and more stable than the release state above a specific threshold nearfild strength. We have also estimated the decrease in the capture free-energy profile and the increase in the release profiles to be around 5 kJ mol⁻¹ for the laser powers employed, ranging from laser-OFF conditions to 11 mW μm⁻². We envisage that our findings can be combined with the electrocatalytic capabilities of the (nearfield) nanogap to develop next-generation molecular nanoreactors. This approach will open the door to highly efficient SM catalysis with precise extended monitoring timescales facilitated through the longer residence times of the reactant trapped inside the nanogap.

中文翻译：

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用单分子玩捕捉和释放：对等离子体控制的纳米间隙的机械洞察

单分子 (SM) 检测对于研究分子水平的过程至关重要。在过去十年中，基于纳米间隙的检测方法已被证明是高度准确的 SM 捕获和检测平台。不幸的是，这些方法面临着几个固有的缺点，例如检测时间短和布朗运动的影响，这些都可能阻碍分子捕获。基于纳米间隙的 SM 检测方法已成功与基于光学的设置耦合，以利用近场辅助捕获来克服这些缺点，从而改进 SM 捕获和检测。在这里，我们使用基于隐马尔可夫模型的无监督机器学习方法，首次对纳米间隙中 SM 捕获和释放的近场效应进行了机械研究。我们表明近场强度可以操纵 SM 捕获和释放过程的动力学。随着场强的增加，捕获动力学的速率常数增加，而释放动力学降低，前者优于后者。因此，SM 捕获状态比特定阈值 nearfild 强度以上的释放状态更有可能和更稳定。我们还估计捕获自由能曲线的减少和释放曲线的增加约为 5 kJ mol^-1表示所采用的激光功率，范围从激光关闭条件到 11 mW μm ^-2。我们设想我们的发现可以与（近场）纳米间隙的电催化能力相结合，以开发下一代分子纳米反应器。这种方法将为高效的 SM 催化打开大门，并通过捕获在纳米间隙内的反应物的较长停留时间促进精确延长监测时间尺度。