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Title: Direct Measurement of Water Permeation in Submerged Alkyl Thiol Self-Assembled Monolayers on Gold Surfaces Revealed by Neutron Reflectometry

Abstract

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. Furthermore these results demonstratemore » that water accesses defects, fluid regions, and heterogeneous domains inherent to even well-formed SAMs.« less

Authors:
 [1]; ORCiD logo [2]; ORCiD logo [3];  [1];  [2]; ORCiD logo [2]; ORCiD logo [2]; ORCiD logo [1]
  1. The Univ. of Texas at Austin, Austin, TX (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. The Univ. of North Carolina at Chapel Hill, Chapel Hill, NC (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1510578
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Langmuir
Additional Journal Information:
Journal Volume: 35; Journal Issue: 16; Journal ID: ISSN 0743-7463
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Fies, Whitney A., Dugger, Jason W., Dick, Jeffrey E., Wilder, Logan M., Browning, Katie L., Doucet, Mathieu, Browning, James F., and Webb, Lauren J. Direct Measurement of Water Permeation in Submerged Alkyl Thiol Self-Assembled Monolayers on Gold Surfaces Revealed by Neutron Reflectometry. United States: N. p., 2019. Web. doi:10.1021/acs.langmuir.9b00541.
Fies, Whitney A., Dugger, Jason W., Dick, Jeffrey E., Wilder, Logan M., Browning, Katie L., Doucet, Mathieu, Browning, James F., & Webb, Lauren J. Direct Measurement of Water Permeation in Submerged Alkyl Thiol Self-Assembled Monolayers on Gold Surfaces Revealed by Neutron Reflectometry. United States. doi:10.1021/acs.langmuir.9b00541.
Fies, Whitney A., Dugger, Jason W., Dick, Jeffrey E., Wilder, Logan M., Browning, Katie L., Doucet, Mathieu, Browning, James F., and Webb, Lauren J. Thu . "Direct Measurement of Water Permeation in Submerged Alkyl Thiol Self-Assembled Monolayers on Gold Surfaces Revealed by Neutron Reflectometry". United States. doi:10.1021/acs.langmuir.9b00541.
@article{osti_1510578,
title = {Direct Measurement of Water Permeation in Submerged Alkyl Thiol Self-Assembled Monolayers on Gold Surfaces Revealed by Neutron Reflectometry},
author = {Fies, Whitney A. and Dugger, Jason W. and Dick, Jeffrey E. and Wilder, Logan M. and Browning, Katie L. and Doucet, Mathieu and Browning, James F. and Webb, Lauren J.},
abstractNote = {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. Furthermore these results demonstrate that water accesses defects, fluid regions, and heterogeneous domains inherent to even well-formed SAMs.},
doi = {10.1021/acs.langmuir.9b00541},
journal = {Langmuir},
number = 16,
volume = 35,
place = {United States},
year = {2019},
month = {3}
}

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This content will become publicly available on March 28, 2020
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