Surface-dependent chemical equilibrium constants and capacitances for bare and 3-cyanopropyldimethylchlorosilane coated silica nanochannels

Mathias Bækbo Andersen, Jared Frey, Sumita Pennathur, Henrik Bruus

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    We present a combined theoretical and experimental analysis of the solid–liquid interface of fused-silica nanofabricated channels with and without a hydrophilic 3-cyanopropyldimethylchlorosilane (cyanosilane) coating. We develop a model that relaxes the assumption that the surface parameters C1, C2, and pK+ are constant and independent of surface composition. Our theoretical model consists of three parts: (i) a chemical equilibrium model of the bare or coated wall, (ii) a chemical equilibrium model of the buffered bulk electrolyte, and (iii) a self-consistent Gouy–Chapman–Stern triple-layer model of the electrochemical double layer coupling these two equilibrium models. To validate our model, we used both pH-sensitive dye-based capillary filling experiments as well as electro-osmotic current-monitoring measurements. Using our model we predict the dependence of ζ potential, surface charge density, and capillary filling length ratio on ionic strength for different surface compositions, which can be difficult to achieve otherwise.
    Original languageEnglish
    JournalJournal of Colloid and Interface Science
    Volume353
    Issue number1
    Pages (from-to)301-310
    ISSN0021-9797
    DOIs
    Publication statusPublished - 2011

    Keywords

    • Cyanosilane surface coating
    • Capillary filling
    • Nanofluidics
    • Gouy–Chapman–Stern triple-layer model
    • Silica nanochannels

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