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Title: Unraveling the dynamics and structure of functionalized self-assembled monolayers on gold using 2D IR spectroscopy and MD simulations

Functionalized self-assembled monolayers (SAMs) are the focus of ongoing investigations because they can be chemically tuned to control their structure and dynamics for a wide variety of applications, including electrochemistry, catalysis, and as models of biological interfaces. In this paper, we combine reflection 2D infrared vibrational echo spectroscopy (R-2D IR) and molecular dynamics simulations to determine the relationship between the structures of functionalized alkanethiol SAMs on gold surfaces and their underlying molecular motions on timescales of tens to hundreds of picoseconds. We find that at higher head group density, the monolayers have more disorder in the alkyl chain packing and faster dynamics. The dynamics of alkanethiol SAMs on gold are much slower than the dynamics of alkylsiloxane SAMs on silica. Finally, using the simulations, we assess how the different molecular motions of the alkyl chain monolayers give rise to the dynamics observed in the experiments.
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Stanford Univ., CA (United States). Dept. of Chemistry
Publication Date:
Grant/Contract Number:
SC0014437; FA9550-16-1-0104
Type:
Published Article
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 113; Journal Issue: 18; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Research Org:
Stanford Univ., CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); US Air Force Office of Scientific Research (AFOSR)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; self-assembled monolayer; dynamics; 2D IR spectroscopy; MD simulation
OSTI Identifier:
1245295
Alternate Identifier(s):
OSTI ID: 1469314

Yan, Chang, Yuan, Rongfeng, Pfalzgraff, William C., Nishida, Jun, Wang, Lu, Markland, Thomas E., and Fayer, Michael D.. Unraveling the dynamics and structure of functionalized self-assembled monolayers on gold using 2D IR spectroscopy and MD simulations. United States: N. p., Web. doi:10.1073/pnas.1603080113.
Yan, Chang, Yuan, Rongfeng, Pfalzgraff, William C., Nishida, Jun, Wang, Lu, Markland, Thomas E., & Fayer, Michael D.. Unraveling the dynamics and structure of functionalized self-assembled monolayers on gold using 2D IR spectroscopy and MD simulations. United States. doi:10.1073/pnas.1603080113.
Yan, Chang, Yuan, Rongfeng, Pfalzgraff, William C., Nishida, Jun, Wang, Lu, Markland, Thomas E., and Fayer, Michael D.. 2016. "Unraveling the dynamics and structure of functionalized self-assembled monolayers on gold using 2D IR spectroscopy and MD simulations". United States. doi:10.1073/pnas.1603080113.
@article{osti_1245295,
title = {Unraveling the dynamics and structure of functionalized self-assembled monolayers on gold using 2D IR spectroscopy and MD simulations},
author = {Yan, Chang and Yuan, Rongfeng and Pfalzgraff, William C. and Nishida, Jun and Wang, Lu and Markland, Thomas E. and Fayer, Michael D.},
abstractNote = {Functionalized self-assembled monolayers (SAMs) are the focus of ongoing investigations because they can be chemically tuned to control their structure and dynamics for a wide variety of applications, including electrochemistry, catalysis, and as models of biological interfaces. In this paper, we combine reflection 2D infrared vibrational echo spectroscopy (R-2D IR) and molecular dynamics simulations to determine the relationship between the structures of functionalized alkanethiol SAMs on gold surfaces and their underlying molecular motions on timescales of tens to hundreds of picoseconds. We find that at higher head group density, the monolayers have more disorder in the alkyl chain packing and faster dynamics. The dynamics of alkanethiol SAMs on gold are much slower than the dynamics of alkylsiloxane SAMs on silica. Finally, using the simulations, we assess how the different molecular motions of the alkyl chain monolayers give rise to the dynamics observed in the experiments.},
doi = {10.1073/pnas.1603080113},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = 18,
volume = 113,
place = {United States},
year = {2016},
month = {4}
}