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Abstract In this paper, we highlight the uniqueness of nanoporous film‐coated electrodes as electrochemical sensing platforms. Specifically, we focus on discussing electrodes coated with insulator‐based monolithic films comprising vertically‐oriented, rigid cylindrical nanopores of uniform diameters (2–200 nm). The electrode coating results in the formation of an array of recessed nanodisk electrodes, and thus we named them recessed nanodisk‐array electrodes (RNEs). We first summarize the properties of nanoporous films commonly used for RNE fabrication, including nanoporous anodic alumina membranes, track‐etched polymer membranes, block copolymer‐derived nanoporous films, and mesoporous silica films. Subsequently, we discuss representative works that take advantage of the uniform size/shape of the nanopores for enhancing electrochemical detection selectivity and sensitivity. RNE‐based sensors measure faradaic currents from redox‐active analytes or exogenously‐added electroactive species that penetrate through the nanopores, or those from redox‐active moieties tethered to the surface of the nanopores or underlying electrodes. The enhanced detection selectivity of these sensors is attributed to the preferential partitioning of analytes into the nanopores or steric/electrostatic exclusion of interfering species. In particular, the uniform sizes/shapes of RNE nanopores play key roles in their higher molecular sieving selectivity and also in the better control of the detection selectivity based on electrostatic/chemical interactions. The detection sensitivity of RNE‐based sensors can be improved by tailoring the chemical environments of the nanopores for analyte preconcentration or for steric/electrostatic manipulation of the dynamics of redox‐tagged binding moieties. These unique characteristics of RNEs, in addition to the mitigation of electrode fouling by the nanoporous films, will enable the development of pretreatment‐free electrochemical sensors for complex matrix solutions.
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Spontaneous outflow efficiency of confined liquid in hydrophobic nanopores
The suspension of nanoporous particles in a nonwetting liquid provides a unique solution to the crux of superfluid, sensing, and energy conversion, yet is challenged by the incomplete outflow of intruded liquid out of nanopores for the system reusability. We report that a continuous and spontaneous liquid outflow from hydrophobic nanopores with high and stable efficiency can be achieved by regulating the confinement of solid–liquid interactions with functionalized nanopores or/and liquids. Full-scale molecular-dynamics simulations reveal that the grafted silyl chains on nanopore wall surfaces will promote the hydrophobic confinement of liquid molecules and facilitate the molecular outflow; by contrast, the introduction of ions in the liquid weakens the hydrophobic confinement and congests the molecular outflow. Both one-step and multistep well-designed quasistatic compression experiments on a series of nanopores/nonwetting liquid material systems have been performed, and the results confirm the outflow mechanism in remarkable agreement with simulations. This study offers a fundamental understanding of the outflow of confined liquid from hydrophobic nanopores, potentially useful for devising emerging nanoporous-liquid functional systems with reliable and robust reusability.
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- PAR ID:
- 10195177
- Publisher / Repository:
- Proceedings of the National Academy of Sciences
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 117
- Issue:
- 41
- ISSN:
- 0027-8424
- Page Range / eLocation ID:
- p. 25246-25253
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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