Abstract While the electrical models of the membrane-based solid-state nanopores have been well established, silicon-based pyramidal nanopores cannot apply these models due to two distinctive features. One is its 35.3° half cone angle, which brings additional resistance to the moving ions inside the nanopore. The other is its rectangular entrance, which makes calculating the access conductance challenging. Here, we proposed and validated an effective transport model (ETM) for silicon-based pyramidal nanopores by introducing effective conductivity. The impact of half cone angle can be described equivalently using a reduced diffusion coefficient (effective diffusion coefficient). Because the decrease of diffusion coefficient results in a smaller conductivity, effective conductivity is used for the calculation of bulk conductance in ETM. In the classical model, intrinsic conductivity is used. We used the top-down fabrication method for generating the pyramidal silicon nanopores to test the proposed model. Compared with the large error (≥25% in most cases) when using the classical model, the error of ETM in predicting conductance is less than 15%. We also found that the ETM is applicable when the ratio of excess ion concentration and bulk ion concentration is smaller than 0.2. At last, it is proved that ETM can estimate the tip size of pyramidal silicon nanopore. We believe the ETM would provide an improved method for evaluating the pyramidal silicon nanopores.
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Biomimetic potassium-selective nanopores
Reproducing the exquisite ion selectivity displayed by biological ion channels in artificial nanopore systems has proven to be one of the most challenging tasks undertaken by the nanopore community, yet a successful achievement of this goal offers immense technological potential. Here, we show a strategy to design solid-state nanopores that selectively transport potassium ions and show negligible conductance for sodium ions. The nanopores contain walls decorated with 4′-aminobenzo-18-crown-6 ether and single-stranded DNA (ssDNA) molecules located at one pore entrance. The ionic selectivity stems from facilitated transport of potassium ions in the pore region containing crown ether, while the highly charged ssDNA plays the role of a cation filter. Achieving potassium selectivity in solid-state nanopores opens new avenues toward advanced separation processes, more efficient biosensing technologies, and novel biomimetic nanopore systems.
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- Award ID(s):
- 1803002
- NSF-PAR ID:
- 10094749
- Date Published:
- Journal Name:
- Science Advances
- Volume:
- 5
- Issue:
- 2
- ISSN:
- 2375-2548
- Page Range / eLocation ID:
- eaav2568
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Redox probe transport through supported lipid bilayers and nanopore‐confined lipid assemblies on silica thin films is examined using electrochemical impedance spectroscopy (EIS). These supported lipid systems are emerging biomimetic separation and sensor platforms. The ability to quantify the accessibility of the pore structure of the mesoporous silica thin films is demonstrated, which is essential for the incorporation of carriers into the lipids for selective solute transport. Redox probe molecules with varying hydrophilicity are used to compare ion transport in supported lipid pore‐spanning bilayers (enveloped bilayers) and novel lipid filled pores of mesoporous silica thin films. The films feature orthogonally oriented 8–10 nm cylindrical nanopores formed by deposition of P123‐templated silica sols onto chemically modified fluorine‐doped tin oxide. Nanopore accessibility is confirmed by EIS with hydrophilic probe 1,1′‐ferrocenedimethanol (FDM). Filling the pores with lipid 1,2‐dipalmitoyl‐sn‐glycero‐3‐phosphocholine results in a superior barrier (with roughly 1/9 the permeability) to transport of FDM compared to fragile enveloped lipid bilayers deposited by vesicle fusion. The pore‐confined lipids not only provide a better barrier to FDM, but also a better pathway for the transport across the films of a hydrophobic redox probe 1,1′‐dioctadecyl‐4,4′‐bipyridinium dibromide, with an ideal transport selectivity of 11 compared to FDM.
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Abstract Recent studies of the high energy‐conversion efficiency of the nanofluidic platform have revealed the enormous potential for efficient exploitation of electrokinetic phenomena in nanoporous membranes for clean‐energy harvesting from salinity gradients. Here, nanofluidic reverse electrodialysis (NF‐RED) consisting of vertically aligned boron‐nitride‐nanopore (VA‐BNNP) membranes is presented, which can efficiently harness osmotic power. The power density of the VA‐BNNP reaches up to 105 W m−2, which is several orders of magnitude higher than in other nanopores with similar pore sizes, leading to 165 mW m−2of net power density (i.e., power per membrane area). Low‐pressure chemical vapor deposition technology is employed to uniformly deposit a thin BN layer within 1D anodized alumina pores to prepare a macroscopic VA‐BNNP membrane with a high nanopore density, ≈108pores cm−2. These membranes can resolve fundamental questions regarding the ion mobility, liquid transport, and power generation in highly charged nanopores. It is shown that the transference number in the VA‐BNNP is almost constant over the entire salt concentration range, which is different from other nanopore systems. Moreover, it is also demonstrated that the BN deposition on the nanopore channels can significantly enhance the diffusio‐osmosis velocity by two orders of magnitude at a high salinity gradient, resulting in a huge increase in power density.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1126/sciadv.aav2568
