Heterogeneous reactions occurring in atmospheric aerosols are crucial components of multiple chemical reaction cycles. Despite the importance of heterogeneous reactions, our ability to predict the outcomes of these reactions is hindered by the complexity of the interfacial region in which they occur. Reverse micelles (RMs) in solution provide a tunable platform for examining the interfacial properties of atmospherically relevant ions. Here we examine the interfacial properties HSO4- within cationic RMs prepared using cetyltrimethylammonium hydrogen sulfate (CTAHS). Infrared spectra of CTAHS RMs were collected and analyzed using multivariate curve resolution-alternating least squares (MCR-ALS). MCR-ALS analysis reveals that four distinct species contribute to the observed infrared spectra, which we assign as: CTA+ HSO4- contact pairs, interfacial HSO4-, core HSO4-, and core SO42-. Computational studies reveal that the CTA+ HSO4- contact pairs exist in two distinct orientations at the interface. Spectral contributions from each chemical species are used to determine quantitative interfacial affinity (χInt.) for HSO4-.

Orientation and partitioning of hydrogen sulfate in reverse micelle structures

ACS Fall 2021

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