Organic Constituents on the Surfaces of Aerosol Particles from Southern Finland, Amazonia, and California Studied by Vibrational Sum Frequency Generation

Abstract

This article summarizes and compares the analysis of the surfaces of natural aerosol particles from three different forest environments by vibrational sum frequency generation. The experiments were carried out directly on filter and impactor substrates, without the need for sample preconcentration, manipulation, or destruction. We discuss the important first steps leading to secondary organic aerosol (SOA) particle nucleation and growth from terpene oxidation by showing that, as viewed by coherent vibrational spectroscopy, the chemical composition of the surface region of aerosol particles having sizes of 1 μm and lower appears to be close to size-invariant. We also discuss the concept of molecular chirality as a chemical marker that could be useful for quantifying how chemical constituents in the SOA gas phase and the SOA particle phase are related in time. Finally, we describe how the combination of multiple disciplines, such as aerosol science, advanced vibrational spectroscopy, meteorology, and chemistry can be highly informative when studying particles collected during atmospheric chemistry field campaigns, such as those carried out during HUMPPA-COPEC-2010, AMAZE-08, or BEARPEX-2009, and when they are compared to results from synthetic model systems such as particles from the Harvard Environmental Chamber (HEC). Discussions regarding the future of SOA chemical analysis approaches are given in the context of providing a path toward detailed spectroscopic assignments of SOA particle precursors and constituents and to fast-forward, in terms of mechanistic studies, through the SOA particle formation process.

Vibrational Sum Frequency Generation Spectroscopy of Secondary Organic Material Produced by Condensational Growth from α-Pinene Ozonolysis

“…20,31 The sample was moved so that at least three spots were analyzed per sample. The SFG spectra were recorded at the same incident up-converter pulse energy.…”

“…20,31 Both sets of spectra are similar to those obtained from particles collected at a field site in Southern Finland. 20,31 The SFG spectra show one dominant peak near 2950 cm −1 for both condensational and coagulative growth regimes.…”

Enhanced Stability of a Carbon Monoxide Monolayer Adsorbed on Platinum under Electrochemical Control Probed by Sum-Frequency Generation Spectroscopy

“…Whatever the environment where they occur (gas, liquid), the monitoring and fundamental understanding of these molecular reactions at the surface of the catalyst require the use of sensitive and selective analytical and spectroscopic tools. [4][5][6][7][8][9][10][11][12][13] Nonlinear Sum-Frequency Generation spectroscopy (SFG) [14][15][16][17][18][19][20][21][22] is a powerful in situ probe of the surface coverage and adsorption geometry in a reactor [23][24][25][26][27][28] , as well as in a spectro-electrochemical cell. In the latter case, the electric potential applied across the surface controls the chemical reaction and the structure of the electrodeelectrolyte interface 29 .…”

Towards the identification of molecular constituents associated with the surfaces of isoprene-derived secondary organic aerosol (SOA) particles

“…Formation of 2-methyltetraols occurs primarily through the reactive uptake of IEPOX into aerosols by acid-catalyzed epoxide ring opening followed by nucleophilic addition (Surratt et al, 2010). As part of this work, we focus on the epoxides (Paulot et al, 2009) and tetraols (Claeys et al, 2004) that have been proposed to be present in the SOA particles and that are characterized by oxygen-tocarbon (O/C) ratios that fall into the 0.4 ± 0.1 range typical for SOA particles in tropical forests (Ebben et al, 2012). Following a brief description of the synthesis and the analytical methods, we characterize the compounds prepared here by a variety of physical measurements and surface-selective spectroscopic probes.…”