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A high rectification ratio nanofluidic diode induced by an "ion pool".

ABSTRACT: Inspired by functionalized biological ion channels, artificial channels were prepared to mimic the natural ones. The key concept behind the rectifying phenomena in nanochannels is the construction of asymmetric restrictive nanochannels. Here, we prepared nanoporous oxidized polyvinyl alcohol (PVA) and WO₃ composite coatings on hourglass-shaped anodic aluminum oxide (AAO) nanochannel surfaces. Accordingly, a special "ion pool" is formed between the homogeneous junction in the middle of the AAO and the nanoporous PVA/WO₃ film-covered AAO surface and its two ends are greatly nano-confined. Ion enrichment and ion depletion occur in the "ion pool" and are dependant on the applied voltage polarity. A rectification ratio of 458, which is in accordance with the highest value found in previous reports, was obtained from the cooperative effects of the two small open ends of the "ion pool". Furthermore, this value is enhanced to about 2000 under constant voltage. An excellent pH-sensitive rectification property, with a single rectification direction from acidic to basic conditions, has also been demonstrated.

SUBMITTER: Liu Q

PROVIDER: S-EPMC9049848 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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A high rectification ratio nanofluidic diode induced by an "ion pool".

Liu Qingqing Q Liu You Y Lu Bingxin B Wang Yuting Y Xu Yanglei Y Zhai Jin J Fan Xia X

RSC advances 20200218 13

Inspired by functionalized biological ion channels, artificial channels were prepared to mimic the natural ones. The key concept behind the rectifying phenomena in nanochannels is the construction of asymmetric restrictive nanochannels. Here, we prepared nanoporous oxidized polyvinyl alcohol (PVA) and WO<sub>3</sub> composite coatings on hourglass-shaped anodic aluminum oxide (AAO) nanochannel surfaces. Accordingly, a special "ion pool" is formed between the homogeneous junction in the middle of ...[more]

PMID: 35492185

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Project description:We propose herein a unique mechanism of generating tunable surface charges in a metal-dielectric Janus nanopore for the development of nanofluidic ion diode, wherein an uncharged metallic nanochannel is in serial connection with a dielectric nanopore of fixed surface charge. In response to an external electric field supplied by two probes located on both sides of the asymmetric Janus nanopore, the metallic portion of the nanochannel is electrochemically polarized, so that a critical junction is formed between regions with an enriched concentration of positive and negative ions in the bulk electrolyte adjacent to the conducting wall. The combined action of the field-induced bipolar induced double layer and the native unipolar double layer full of cations within the negatively-charged dielectric nanopore leads to a voltage-controllable heterogenous volumetric charge distribution. The electrochemical transport of field-induced counterions along the nanopore length direction creates an internal zone of ion enrichment/depletion, and thereby enhancement/suppression of the resulting electric current inside the Janus nanopore for reverse working status of the nanofluidic ion diode. A mathematical model based upon continuum mechanics is established to study the feasibility of the Janus nanochannel in causing sufficient ion current rectification, and we find that only a good matching between pore diameter and Debye length is able to result in a reliable rectifying functionality for practical applications. This rectification effect is reminiscent of the typical bipolar membrane, but much more flexible on account of the nature of a voltage-based control due to induced-charge electrokinetic polarization of the conducting end, which may hold promise for osmotic energy conversion wherein an electric current appears due to a difference in salt concentration. Our theoretical demonstration of a composite metal-dielectric ion-selective medium provides useful guidelines for construction of flexible on-chip platforms utilizing induced-charge electrokinetic phenomena for a high degree of freedom ion current control.

Dataset Information

A high rectification ratio nanofluidic diode induced by an "ion pool".

Publications

A high rectification ratio nanofluidic diode induced by an "ion pool".

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