Atmospheric β-Caryophyllene-Derived Ozonolysis Products at Interfaces

Abstract

By integrating organic synthesis, secondary organic aerosol synthesis and collection, density functional theory (DFT) calculations, and vibrational sum frequency generation (SFG) spectroscopy, we identify close spectral matches between the surface vibrational spectra of β-caryophyllene-derived secondary organic material (SOM) and those of β-caryophyllene aldehyde and β-caryophyllonic acid at various interfaces. Combined with the record high surface tension depression described previously for these same oxidation products, we discuss possibilities for an intrinsically chemical origin for cloud activation by terpene-derived surfactants. Although the present study does not unequivocally identify the synthesized and analyzed oxidation products on the β-caryophyllene-derived SOM surfaces, these two compounds appear to be the most surface active out of the series and have also been foci of previous β-caryophyllene field and laboratory studies. An orientation analysis by phase-resolved SFG spectroscopy reveals a “pincer-like” configuration of the β-caryophyllene oxidation products, albeit on a model quartz surface, that somewhat resembles the orientation of inverse double-tailed surfactants at the surfaces of biological systems. The structural information suggests that the less polar moiety of a surface-localized oxidation product, such as those studied here, may be the first site-of-contact for a gas-phase molecule approaching an SOA particle containing surface-active β-caryophyllene oxidation products.

Ch3MS-RF: a random forest model for chemical characterization and improved quantification of unidentified atmospheric organics detected by chromatography–mass spectrometry techniques

“…The selection of these standard species was informed by previous work targeting similar sample types, using the same instrumentation (Worton et al, 2011;Zhang et al, 2018), and covers species including sugars, polycyclic aromatic hydrocarbons (PAHs), and both monoterpene and isoprene oxidation products. In addition to commercially available external standards, six sesquiterpene oxidation products were custom synthesized by collaborators (as described in Bé et al, 2019), for expanded coverage of potentially important chemical tracers. The full list of standard components can be found in Table A1, and the standard property distribution in volatility-polarity space is illustrated in Fig.…”

Binding and Orientation of Carbamate Pesticides on Silica Surfaces

“…Phase-resolved measurements here are based on the internal heterodyne method, where a freshly cleaned z -cut α-crystalline quartz window was used as a substrate instead (see the SI). ,, In summary, when the vSFG spectrum of a sample on the z -cut α crystal quartz surface is measured, the vSFG response has contributions from the bulk of the z -cut α quartz crystal (internal local oscillator) and from the molecules adsorbed on the quartz crystal surface. A detailed phase-resolved SFG study by Wang et al showed the application of the internal heterodyne method by utilizing the azimuthal angle phase dependence of the right-handed z -cut α quartz crystal. , In our experiment, carbaryl I ± x Norm SSP and PPP spectra on quartz were obtained at azimuthal angles of Φ = 0° (+ x axis) and Φ = 180° (− x axis) by a 15 s acquisition and normalized to nonresonant response of the bare z -cut α quartz crystal under the + x direction (see the SI).…”

“…Here, we primarily focus on the interfacial structure and the surface anchoring mechanism of carbaryl on silica using a combination of surface-selective nonlinear vibrational spectroscopy and computational modeling, including molecular dynamics (MD) simulations and ab initio calculations of vibrational spectra. Raman and Fourier transform infrared (FTIR) vibrational spectroscopic methods have been widely applied to study pesticides in bulk solutions and films. ,− Here, we apply vibrational sum frequency generation (vSFG) spectroscopy, an in situ technique particularly suitable for the analysis of molecules at buried interfaces and sensitive to sub-monolayer amounts of adsorbates. ,,− As a coherent nonlinear spectroscopic technique, the vSFG response is highly sensitive to molecular orientation and ordering at the surface, , making vSFG a powerful technique for obtaining detailed chemical information regarding the molecular composition, structure, and interactions of molecules at interfaces. As such, it has become a versatile tool for studies of environmental surfaces and interfaces under ambient conditions ,,− and for revealing structure–activity relationships of surface-immobilized compounds, like antimicrobial coatings. − …”

Virtual Issue in Atmospheric Chemistry Research

“…21 Dissolved organic matter and surface-active organic compounds also modify the hygroscopicity and surface tension of the particles, and hence their propensity to act as cloud condensation nuclei. 22,23 The coating of aqueous droplet surfaces by surfactant organic molecules inhibits dissolution of ambient gases including CO2 with consequences for the droplet pH. 24 Microbe metabolism can change the organic composition of cloud and aerosol droplets, but the density of metabolically active cells in the atmosphere is low.…”