We provide an overview of atom-scale apertures in solid-state membranes, from "pores" and "tubes" to "channels", with characteristic sizes comparable to the sizes of ions and water molecules. In this regime of ∼1 nm diameter pores, water molecules and ions are strongly geometrically confined: the size of water molecules (∼0.3 nm) and the size of "hydrated" ions in water (∼0.7-1 nm) are similar to the pore diameters, physically limiting the ion flow through the hole. The pore sizes are comparable to the classical Debye screening length governing the spatial range of electrostatic interaction, ∼0.3 to 1 nm for 1 to 0.1 M KCl. In such small structures, charges can be unscreened, leading to new effects. We discuss experiments on ∼1 nm diameter nanopores, with a focus on carbon nanotube pores and ion transport studies. Finally, we present an outlook for artificial "size zero" pores in the regime of small diameters and small thicknesses. Beyond mimicking protein channels in nature, solid-state pores may offer additional possibilities where sensing and control are performed at the pore, such as in electrically and optically addressable solid-state materials.

中文翻译：

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离子和水在原子尺度孔中起舞：对“零尺寸”的看法。

我们概述了固态膜中的原子级孔径，从“孔”和“管”到“通道”，其特征尺寸与离子和水分子的尺寸相当。在这种直径约为 1 nm 的孔隙中，水分子和离子在几何上受到强烈限制：水分子的大小（~0.3 nm）和水中“水合”离子的大小（~0.7-1 nm）与孔径，物理限制离子流过孔。孔径与控制静电相互作用空间范围的经典德拜筛选长度相当，对于 1 到 0.1 M KCl，孔径约为 0.3 到 1 nm。在如此小的结构中，电荷可以不被屏蔽，从而产生新的效果。我们讨论了直径约 1 nm 的纳米孔的实验，重点是碳纳米管孔和离子传输研究。最后，我们提出了在小直径和小厚度范围内人工“零尺寸”孔隙的前景。除了模拟自然界中的蛋白质通道外，固态孔隙还可以提供在孔隙中进行传感和控制的额外可能性，例如在电和光学可寻址的固态材料中。