Direct Measurement of Water Permeation in Submerged Alkyl Thiol Self-Assembled Monolayers on Gold Surfaces Revealed by Neutron Reflectometry
| Autor: | Lauren J. Webb, Logan M. Wilder, Mathieu Doucet, Whitney A. Fies, James F. Browning, Katie L. Browning, Jason W. Dugger, Jeffrey E. Dick |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
chemistry.chemical_classification
Solid-state chemistry Materials science Self-assembled monolayer 02 engineering and technology Surfaces and Interfaces Permeation 010402 general chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics Electrochemistry 01 natural sciences 0104 chemical sciences chemistry Chemical engineering Monolayer Thiol General Materials Science Neutron reflectometry 0210 nano-technology Spectroscopy Alkyl |
| Zdroj: | Langmuir : the ACS journal of surfaces and colloids. 35(16) |
| ISSN: | 1520-5827 |
| Popis: | Self-assembled monolayers (SAMs) of alkyl thiols are frequently used to chemically functionalize gold surfaces for applications throughout materials chemistry, electrochemistry, and biotechnology. Despite this, a detailed understanding of the structure of the SAM-water interface generated from both formation and use of the SAM in an aqueous environment is elusive, and analytical measurements of the structure and chemistry of the SAM-water interface are an ongoing experimental challenge. To address this, we used neutron reflectometry (NR) to measure water association with both hydrophobic and hydrophilic SAMs under both wet and dry conditions. SAMs used for this study were made from hydrophobic decanethiol mixed with hydrophilic 11-azido-1-undecanethiol with compositions of 0-100% of the azide-terminated thiol. All SAMs were formed by conventional solution incubation of a Au substrate immersed in ethanol. Each SAM was characterized by grazing incidence angle reflection-absorption Fourier transfer infrared spectroscopy, contact angle goniometry, and electrochemical methods to confirm it was a completely formed monolayer with evidence of extensive crystalline-like domains. NR measured significant absorption of water into each SAM, ranging from 1.6 to 5.7 water molecules per alkyl thiol, when SAMs were immersed in water. Water infiltration was independent of SAM composition and terminal group hydrophilicity. These results demonstrate that water accesses defects, fluid regions, and heterogeneous domains inherent to even well-formed SAMs. |
| Databáze: | OpenAIRE |
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