Noh Yechan, Smolyanitsky Alex
Department of Physics, University of Colorado Boulder, Boulder, Colorado 80305, United States.
Applied Chemicals and Materials Division, National Institute of Standards and Technology, Boulder, Colorado 80305, United States.
J Phys Chem B. 2025 May 15;129(19):4851-4859. doi: 10.1021/acs.jpcb.5c00921. Epub 2025 May 6.
The interplay of interactions between aqueous ions and the confinement of subnanoscale pores in solid 2D membranes causes a range of barrier-limited phenomena, including selective ion trapping and permeation, mechanosensitive transport, and memristive effects. A clear understanding of the transition from diffusive to barrier-limited transport regime is lacking, however. Moreover, the limits of applicability for the analytical formalism widely used to relate measured transport data to the effective pore size are unclear. Here, with the goal of identifying the transition between regimes and determining the pore sizes below which the diffusive formalism fails, we present a computational study of water-dissociated alkali salt transport through 2D membranes featuring pores of various sizes. Triangular nitrogen-terminated multivacancies in hexagonal boron nitride are used as a simple yet illustrative example of uncharged locally dipolar pores with various degrees of cation selectivity. We find that selectivity and high mechanosensitivity are the clearest indicators of the barrier-limited regime onset. We also show that for triangular pore geometries, the diffusion-based analytical formalism is expected to fail when the side of the triangle is below order ≈2 nm. For circular geometries, similar failure is expected for pore diameters below ≈1.2 nm. Because an extensive theoretical description of barrier-limited transport is a major challenge, detailed computer models currently remain the most accurate nonexperimental methods for investigating ion transport in the barrier-limited regime. Given how sensitively the permeation regime depends on the pore size, our results suggest that in addition to advances in fabrication, accurate theoretical interpretation of measured transport data is vital to harnessing the unique features of barrier-limited ionic and molecular transport in nanofluidic systems using nanoporous 2D materials.
水溶液中的离子与固体二维膜中亚纳米级孔隙的限制之间的相互作用会引发一系列受势垒限制的现象，包括选择性离子捕获与渗透、机械敏感传输以及忆阻效应。然而，目前尚缺乏对从扩散传输到势垒限制传输机制转变的清晰理解。此外，广泛用于将测量的传输数据与有效孔径相关联的分析形式体系的适用范围尚不明确。在此，为了确定不同机制之间的转变，并确定扩散形式体系失效时的孔径大小，我们对通过具有各种孔径的二维膜的水解离碱金属盐传输进行了计算研究。六方氮化硼中的三角形氮端基多空位被用作具有不同程度阳离子选择性的不带电局部偶极孔的一个简单但具有代表性的例子。我们发现选择性和高机械敏感性是势垒限制机制开始的最明显指标。我们还表明，对于三角形孔几何形状，当三角形边长小于约2 nm时，基于扩散的分析形式体系预计会失效。对于圆形几何形状，当孔径小于约1.2 nm时，预计会出现类似的失效情况。由于对势垒限制传输进行广泛的理论描述是一项重大挑战，详细的计算机模型目前仍然是研究势垒限制机制下离子传输最准确的非实验方法。鉴于渗透机制对孔径大小的敏感依赖性，我们的结果表明，除了制造技术的进步之外，对测量传输数据进行准确的理论解释对于利用纳米多孔二维材料在纳米流体系统中势垒限制离子和分子传输的独特特性至关重要。
