Size‐Based Cationic Molecular Sieving through Solid‐State Nanochannels

Abstract

filled with electrolyte solutions and the transport of molecules or ions through the pores provides the relevant information required for each particular application. This transport is regulated by the channel size and the physico-chemical characteristics of the channel surface. In biological membranes, the high selectivity and fast ion transport achieved are also ascribed to the precise channel size and functional groups distributed along the channel surface. [24-26] A wide range of experimental techniques are available to tune the channel diameter and surface chemistry to enhance ionic selectivity. They include the preparation of hybrid biological/artificial solid-state membranes, [27,28] channel size tuning through electroless [12,29,30] and atomic layer [31-33] depositions, the grafting of polymer brushes on the channel surface, [34-38] and the deposition of an atomically thin graphene layer on the porous membrane. [39,40] Molecular filtration and discrimination have been achieved using different membranes. For example, Martin and co-workers have employed gold-coated nanochannels for the separation of organic molecules and drug enantiomers based on their charge or molecular size. [12,29,30] Stroeve et al. have demonstrated the pH-responsive transport of ions and biomolecules [41] and Savariar et al. the molecular size-, charge-, and hydrophobicity-based discrimination of organic molecules and proteins [14] using modified nanoporous membranes. Recently, polymer membranes with subnanometer pores have been obtained without specific chemical treatments. For example, track-UV techniques have been employed to fabricate subnanopores which exhibited highly selective and ultrafast ion sieving behavior. [42,43] Moreover, subnanometer pores in metal-organic frameworks integrated inside the bullet-shaped nanochannels of a polymer membrane also exhibited high selectivity towards alkali cations while rejecting divalent ions. [44,45] Recently, we have developed a soft-etch technique to obtain nanochannels in polyimide (PI) membranes irradiated with heavy ions. [46] PI exhibits high chemical, electrical, and heat resistance. Therefore, the chemical etching of ion tracks in PI membranes requires harsh conditions. Usually, the ion tracks in PI are etched with a strong inorganic etchant (chlorine in hypochlorite) at high temperature. Contrary to chemical etching, in a soft-etching technique, the ion tracked PI membranes are exposed to an organic solvent which selectively dissolves the damage trails (latent tracks) caused by the energetic The molecular sieving behavior of soft-etched polyimide membranes having negatively charged nanochannels is described experimentally and theoretically using alkali metal-crown ether cationic complexes and alkylammonium cations. To this end, the electrical conduction and current rectification obtained with different alkali electrolyte solutions (LiCl, NaCl, and KCl) and crown ether molecules (12-crown-4, 15-crown-5, and 18-crown-6) are studied. The results suggest that only the [Li(12C4)] + comp...

Heat and osmosis cooperatively driven power generation in robust two-dimensional hybrid nanofluidic channels

“…4,5 In recent years, membrane systems with nanouidic channels were applied to achieve selective ion diffusion across the nanochannels, which provided a platform for the energy conversion from salinity or temperature gradients into electric power. [6][7][8][9][10][11][12][13][14][15][16] In nanochannel-based power generators, the conversion performance is generally evaluated by using the output power density, which is affected by the ion selectivity and ion permeability of the nanochannel membranes. [17][18][19][20][21][22] Recently, two-dimensional (2D) nanochannels have emerged as potential membrane materials for energy conversion.…”

Nanochannels with a 18-nm feature size and ultrahigh aspect ratio on silica through surface assisting material ejection

“…Nanochannels are widely investigated in many key biomedical and environmental fields, such as nanofluidics, 1 – 3 molecular sieves, 4 , 5 and artificial membranes 6 – 8 However, it is still a big challenge to realize nanochannels on hard and brittle materials, which show great chemical stabilities and can be applied in many harsh environments.…”

Fabrication of Redox-Controllable Bioinspired Nanochannels for Precisely Regulating Protein Transport

“…Recently, an artificial solid-state nanochannel has been developed and utilized to explore the physiological processes and biological functions of their bio-counterparts in vitro. − Particularly, an artificial nanochannel has the prominent advantage of overcoming the fragile structure of the biological channel in protein transport investigation. − To enable the precise adjustment of the transport feature of substances, the functional units are always introduced into the bare nanochannels. − Thus far, we and other groups have successfully utilized such nanochannel-based systems to investigate the transport properties of various ions, small molecules, chiral drugs, and biomolecules. − Despite this major progress in ion and small molecule transport, highly selective and efficient transport of biomacromolecules (e.g., protein) is still a nontrivial task in restricted artificial nanochannels. − Given the abovementioned challenges, we are motivated to design/fabricate bioinspired nanochannels in a new approach, which are expected to possess high performance and controllability for precise biomacromolecule transport.…”