TY - JOUR
T1 - Unanticipated Hydrophobicity Increases of Squalene and Human Skin Oil Films Upon Ozone Exposure
AU - Butman, Jana L.
AU - Thomson, Regan J.
AU - Geiger, Franz M.
N1 - Funding Information:
This work was made possible by the Alfred P. Sloan Foundation through grant G-2019-12300. This work also made use of the Keck-II and SPID facility of Northwestern University’s NUANCE Center, which has received support from the SHyNE Resource (NSF ECCS-2025633), the International Institute for Nanotechnology (IIN), and Northwestern’s MRSEC program (NSF DMR-1720139).
Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.
PY - 2022/11/17
Y1 - 2022/11/17
N2 - The C-H and O-H oscillators on the surfaces of thin films of human-derived skin oil and squalene are probed under ambient conditions (300 K, 1 atm total pressure, 40% RH) using second-order vibrational spectroscopy and contact angle goniometry before and after exposure to ppb amounts of ozone. Skin oil and squalene are found to produce different vibrational sum frequency generation spectra in the C-H stretching region, while exposure to ozone results in surface spectra for both materials that is consistent with a loss of C-H oscillators. The measured contact angles show that the hydrophobicity of the films increases following exposure to ozone, consistent with the reduction in C=C···H2O ("πH") bonding interactions that is expected from C=C double bond loss due to ozonolysis and indicating that the polar functional groups formed point toward the films' interiors. Implications for heterogeneous indoor chemistry are discussed.
AB - The C-H and O-H oscillators on the surfaces of thin films of human-derived skin oil and squalene are probed under ambient conditions (300 K, 1 atm total pressure, 40% RH) using second-order vibrational spectroscopy and contact angle goniometry before and after exposure to ppb amounts of ozone. Skin oil and squalene are found to produce different vibrational sum frequency generation spectra in the C-H stretching region, while exposure to ozone results in surface spectra for both materials that is consistent with a loss of C-H oscillators. The measured contact angles show that the hydrophobicity of the films increases following exposure to ozone, consistent with the reduction in C=C···H2O ("πH") bonding interactions that is expected from C=C double bond loss due to ozonolysis and indicating that the polar functional groups formed point toward the films' interiors. Implications for heterogeneous indoor chemistry are discussed.
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U2 - 10.1021/acs.jpcb.2c04849
DO - 10.1021/acs.jpcb.2c04849
M3 - Article
C2 - 36331532
AN - SCOPUS:85141711136
SN - 1520-6106
VL - 126
SP - 9417
EP - 9423
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 45
ER -