纳通道的物质传输特性及应用

近年来，随着材料科学、微纳加工技术和微纳尺度物质传输理论的发展，纳通道技术得到了越来越多的研究和关注。纳通道包括生物纳通道和人工纳通道，其孔径通常为1~100 nm。在这一尺度下，通道表面与通道内物质之间的作用概率大大增强，使得纳通道表现出许多与宏观体系不同的物质传输特性，例如通道表面电荷与通道内离子之间的静电作用产生了离子选择性，通道内电化学势的不对称分布产生了离子整流特性，物质传输过程中占据通道产生了阻塞脉冲特性等。纳通道中的这些物质传输特性在传感、分离、能源等领域具有广泛应用，例如通过对纳通道进行功能化修饰可以实现门控离子传输；利用亚纳米尺度的通道可以实现单分子传感；利用通道与传输物质之间的相互作用可以实现离子、分子、纳米粒子的分离；利用纳通道的离子选择性可以在通道内实现电荷分离，将不同形式的能量（如光、热、压力、盐差等）高效转化为电能。纳通道技术是化学、材料科学、纳米技术等多学科的交叉集合，在解决生物、环境、能源等基本问题方面具有良好的前景。该文综述了近10年来与纳通道物质传输理论以及纳通道技术应用相关的前沿研究，梳理了纳通道技术的发展过程，并对其在各个领域的应用进行了总结与展望。

Mass transport properties and applications of nanochannels

With the development of materials science, micro/nano processing technologies, and mass transport theories at the micro/nano scale, nanochannel-based technology has been receiving increasing attention. Nanochannels can be classified as biological and artificial. The size of a nanochannel is typically 1-100 nm, which greatly enhances the interaction between the channel surface and substances inside the channel, inducing several special mass transport properties such as ion selectivity, ionic current rectification, and resistive current pulse. Ion selectivity is caused by the electrostatic interaction between ions and the surface charge of the nanochannel, ionic current rectification arises from the asymmetric distribution of the electrochemical potential inside the nanochannel, and a resistive current pulse is generated by the blocking of the nanochannel during the transport of ions/molecules. By taking advantage of these mass transport properties, nanochannels can be applied to various fields. For example, gated ion transport can be realized by modifying the surface of the nanochannel with functional groups; single-molecule sensing can be realized using sub-nanoscale channels; the separation of ions, molecules, or nanoparticles can be realized by regulating the interaction between the nanochannel and transport substances; and various forms of energy, such as light, heat, and salt gradient, can drive charge separation within the nanochannel and be converted into electricity by harnessing the ion selectivity of the nanochannel. However, despite the achievements in nanochannel-based technology, in-depth exploration of the mass transport properties at the nanoscale and further expansion of its application remain to be realized. For the development of this technology, four major issues need to be addressed: fabrication of a single-atom-thick nanochannel/nanopore membrane, precise control of the nanochannel structure, effective regulation of the surface properties of the nanochannel, and enrichment and development of mass transport theories. Nanochannel-based technology requires interdisciplinary efforts at the intersection of chemistry, materials science, and nanotechnology, and shows good promise for solving basic problems in biology, environment, and energy. Herein, we briefly describe the mass transport properties of nanochannels and some emerging developments and applications, and finally provide a brief outlook on this field.