Adsorption at Confined Interfaces
We describe measurements of adsorption between two flat plates when the plates are separated by 0-65 nm. The objective is to examine how adsorption is affected by confinement in very thin films. It is well known that adsorption of simple ions can change with the thickness of a thin film (charge regu...
| Veröffentlicht in: | Langmuir : the ACS journal of surfaces and colloids. - 1985. - 34(2018), 36 vom: 11. Sept., Seite 10469-10479 |
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| Format: | Online-Aufsatz |
| Sprache: | English |
| Veröffentlicht: |
2018
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| Zugriff auf das übergeordnete Werk: | Langmuir : the ACS journal of surfaces and colloids |
| Schlagworte: | Journal Article |
| Zusammenfassung: | We describe measurements of adsorption between two flat plates when the plates are separated by 0-65 nm. The objective is to examine how adsorption is affected by confinement in very thin films. It is well known that adsorption of simple ions can change with the thickness of a thin film (charge regulation); here, we describe a direct method to measure adsorption as a function of confinement and results for one example. Measurement of all separations is achieved simultaneously by measuring visible-light interference in a wedge-shaped crack created between an oxidized silicon wafer and a glass wafer. The adsorbed amount is measured from the fluorescence emission of a dye, after accounting for the optical interference. The specific measurement is of the depletion of a divalent anion, fluorescein, in aqueous solution between two anionic solids, but the measurement could be applied to a range of fluorescent probes. At large separations between the flat plates, the dye is depleted relative to the bulk concentration. At smaller separations, the depletion of the dye decreases. The range of the depletion and the magnitude of depletion decrease with shorter Debye length. Both of these effects are consistent with a simple calculation using the Poisson-Boltzmann equation. There is a multitude of applications where surfactants, polymers, ions, etc. are adsorbed to effect changes in thin films. One example is adsorption designed to alter the stability of colloidal particles |
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| Beschreibung: | Date Completed 07.11.2018 Date Revised 07.11.2018 published: Print-Electronic Citation Status PubMed-not-MEDLINE |
| ISSN: | 1520-5827 |
| DOI: | 10.1021/acs.langmuir.8b01418 |