Surface-Active ß-Caryophyllene Oxidation Products at the Air/Aqueous Interface

Journal Article · Thu Sep 19 00:00:00 EDT 2019 · ACS Earth and Space Chemistry

DOI:https://doi.org/10.1021/acsearthspacechem.9b00185· OSTI ID:1577058

Be, Ariana G. ^[1]; Liu, Yangdongling ^[2]; Tuladhar, Aashish  ^[3]; Bellcross, Aleia D. ^[1]; Wang, Zheming  ^[3]; Thomson, Regan ^[1]; Geiger, Franz M. ^[1]

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1. Northwestern University
2. NORTHWESTERN UNIVERSITY
3. BATTELLE (PACIFIC NW LAB)

We examine synthesized standards of structurally related ß-caryophyllene ozonolysis products at the air/water and air/(NH4)2SO4 (aq) interface using polarization-resolved standard- and high-resolution vibrational sum frequency generation (SFG) spectroscopy in the C–H and O–H stretching regions. ß-Caryophyllene aldehyde (1), the most surface-active molecule in the suite, appears to undergo a change in its molecular orientation distribution when transitioning from low to high relative surface coverage. We also report that the water molecules present at the outermost layer of the aqueous interface are displaced by ß-caryophyllene aldehyde (1) on both the (NH4)2SO4 (aq) and water subphases. Additionally, the more weakly hydrogen-bonded water network observed around ~3400 cm-1 seems to be perturbed to a greater extent by ß-caryophyllene aldehyde (1) than the more strongly hydrogen-bonded population observed at ~3200 cm-1 on the (NH4)2SO4 (aq) subphase, while this effect is not observed on the water subphase. We provide surface spectroscopic evidence for the “salting out” effect of (NH4)2SO4 in aqueous environments and discuss the implications for understanding the organization of surface-localized molecules present in aqueous cloud-forming droplets containing dissolved aerosol cloud condensation nuclei (CCN) in the atmosphere. Despite the importance of elucidating the surface activity and interfacial organization of individual molecules in aqueous media, future work will focus on how the combined effects of several surface-active constituents dictate overall cloud activation potentials of aerosol particles.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1577058
• Report Number(s): PNNL-SA-146722
• Journal Information: ACS Earth and Space Chemistry, Vol. 3, Issue 9
• Country of Publication: United States
• Language: English

Related Subjects

Sum frequency generation (SFG) spectroscopy
?-caryophyllene ozonolysis
sesquiterpene chemistry
air/aqueous interface