On molecular chirality within naturally occurring secondary organic aerosol particles from the central Amazon Basin

Abstract

In this perspectives article, we reflect upon the existence of chirality in atmospheric aerosol particles. We then show that organic particles collected at a field site in the central Amazon Basin under pristine background conditions during the wet and dry seasons consist of chiral secondary organic material. We show how the chiral response from the aerosol particles can be imaged directly without the need for sample dissolution, solvent extraction, or sample preconcentration. By comparing the chiral-response images with optical images, we show that chiral responses always originate from particles on the filter, but not all aerosol particles produce chiral signals. The intensity of the chiral signal produced by the size resolved particles strongly indicates the presence of chiral secondary organic material in the particle. Finally, we discuss the implications of our findings on chiral atmospheric aerosol particles in terms of climate-related properties and source apportionment.

Intrinsic Chirality and Prochirality at Air/R‐(+)‐ and S‐(–)‐Limonene Interfaces: Spectral Signatures With Interference Chiral Sum‐Frequency Generation Vibrational Spectroscopy

“…Measuring the phase relationship of the spectral features in the amide and N‐H bands may provide detailed information on the peptide or protein folding structures. Recently, chiral SFG‐VS has been applied to measure and understand protein and DNA structures at the interface or in the membrane, as well as the chirality of small molecules in the natural secondary organic aerosols from tropical and boreal forests . Such understandings and experimental approaches, as shown in this report, shall certainly help to characterize and to understand the structure and interactions of molecular interfaces and biological membranes.…”

“…Our interest in the limonene molecules is not only because it has been a benchmark choice for studying molecular chirality with various chiroptical and spectroscopic techniques in the bulk, 10,15,[33][34][35][36] but also because of the importance of a class of chiral isoprene and monoterpene molecules, such as limonene and pinene, etc., in the global secondary organic aerosol (SOA) formation and impact on climate changes. [37][38][39][40][41][42] It has been shown that chirality is not only an important component in the SOA, 39,40 the surface structure and reactivity of these SOA particles are also crucial for understanding the transformation and impact of the SOAs. 41,43 We will show that the nearly identical achiral SFG spectra of R-(+)-limonene and S-(-)-limonene, as well as the RS racemic mixture (50/50 equal amount mixture) suggest that the corresponding molecular groups in the R and S enantiomers are with the same interfacial orientations with respect to the interface normal.…”

Photochemical Synthesis of Oligomeric Amphiphiles from Alkyl Oxoacids in Aqueous Environments

“…The SML and the surfaces of aerosols have been shown to contain chiral molecules, including lipids, 109 but these are almost always assumed to be biotic in origin. 14,26,27 However, as demonstrated here, it is possible to make chiral molecules in high yields from very simple, achiral precursors, suggesting that the potential for abiotic environmental sources of chirality should not be discounted.…”

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

“…Although nonlinear optics had been applied to nano-and microparticles before, 153−158 the application of SFG to study atmospheric aerosol particles had not been presented prior to 2011, when our first reports on the subject appeared. 92,159,160 Some considerations regarding SFG signal generation from organic aerosol particles in the micrometer and submicrometer range are given in section IXA.…”