Direct Observation of the Orientational Anisotropy of Buried Hydroxyl Groups inside Muscovite Mica

Journal Article · Mon Jan 07 00:00:00 EST 2019 · Journal of the American Chemical Society

DOI:https://doi.org/10.1021/jacs.8b12483· OSTI ID:1502396

Tuladhar, Aashish  ^[1]; Chase, Zizwe A. ^[2]; Baer, Marcel D. ^[1]; Legg, Benjamin A. ^[3]; Tao, Jinhui ^[1]; Zhang, Shuai  ^[1]; Winkelman, Austin D. ^[2]; Wang, Zheming ^[1]; Mundy, Christopher J.  ^[4]; De Yoreo, James J.  ^[3]; Wang, Hong-fei ^[5]

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1. Physical Sciences Division, Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
2. Physical Sciences Division, Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; School of Chemical and Biological Engineering, Washington State University, Pullman, Washington 99364, United States
3. Physical Sciences Division, Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, United States
4. Physical Sciences Division, Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Department of Chemical Engineering, University of Washington, Seattle, Washington 98195, United States
5. Physical Sciences Division, Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Department of Chemistry and Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200433, China

Muscovite mica (001) is a widely-used model surface for controlling molecular assembly and a common substrate for environmental adsorption processes. The mica (001) surface displays near trigonal symmetry, but many molecular adsorbates — including water — exhibit unequal probabilities of alignment along its three nominally equivalent lattice directions. Buried hydroxyl groups within the muscovite structure are speculated to be responsible, but direct evidence is lacking. Here we utilize vibrational sum frequency generation spectroscopy (vSFG) to characterize the orientation and hydrogen-bonding environment of near-surface hydroxyls inside mica. Multiple distinct peaks are detected in the O-H stretch region, which we attribute to Si/Al substitution in the SiO4 tetrahedron and K+ ion adsorption above the hydroxyls based on density functional theory simulations. Our findings demonstrate that vSFG can identify the absolute orientation of –OH groups and hence the surface termination at a mica surface, providing a means to investigate how –OH groups influence molecular adsorption and better understand mica stacking-sequences and physical behavior.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1502396
• Report Number(s): PNNL-SA-140259
• Journal Information: Journal of the American Chemical Society, Vol. 141, Issue 5; ISSN 0002-7863
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English