Nanopores and nanochannels are ubiquitous, from biological systems to various artificial materials. Taking advantage of size confinement and tailoring the interior components, numerous functions can be achieved such as selectivity, gating, rectification, and so on, which result from diverse interactions between ion/molecule and nanopore/nanochannel. In this Perspective, on account of the summarized critical principles, namely size/shape, wettability, charge, recognition, and other interactions during ion/molecule transportation in nanopores and nanochannels, we introduce four main sections of applications: selective transportation in separation, controllable gating systems, energy conversion devices, and sensors. In addition, some typical challenges and possible future research endeavors in the related fields will also be discussed.

Water wetting behavior in nanoconfined environments plays an important role in mass transport and signal transmission of organisms. It is valuable and challenging to investigate how water behaves in such a nanometer-scale with external stimuli, in particular with electric field and light. Unfortunately, the mechanism of hydrophobic reaction inside the nanospaces is still obscure and lacks experimental support for the current electric-field- or photoresponsive nanochannels which suffer from fragility or monofunctionality. Here, we design functionalized hydrophobic nanopores to regulate ion transport by light and electric field using azobenzene-derivatives-modified polymer nanochannels. With these addressable features, we can control the pore surface wetting behavior to switch the nanochannels between nonconducting and conducting states. Furthermore, we found these hydrophobic nanochannels are rough with a contact angle of 67.3°, making them extremely different from the familiar ones with a smooth pore surface and larger contact angles (>90°). These findings point to new opportunities for studying and manipulating water behavior in nanoconfined environments.

Silicon wafers have been widely used in the semiconductor industry for many decades. Over the past decades, with the development of organic optoelectronic materials, silicon-based organic-inorganic hybrid devices have received more and more interest in fundamental and applied research. To obtain uniform organic films for hybrid devices, superamphiphilic surfaces, on which both water and oil can spread completely, show great advantages. Herein, we prepared superamphiphilic silicon wafer surfaces with contact angles (CAs) near 0° for both water and typical organic liquids. Interestingly, lateral force mode (LFM) atomic force microscopy (AFM) images indicate that the superamphiphilicity is induced by alternating hydrophilic and hydrophobic nanodomains. By making use of these superamphiphilic silicon wafer surfaces, uniform polypyrrole (PPy) films were generated in both water and cyclopentanone, providing a versatile and effective way for the integration of organic optoelectronic materials with inorganic microelectronic devices.