Although freshly emitted black carbon aerosols are constituted largely of hydrophobic carbon particulates (CPs), oxidation and prolonged exposure to other aerosol constituents renders BC particulates more hydrophilic and soluble in aqueous solution. BC aerosols change the structural, elastic, and dynamic properties of biological membranes, but the mechanism(s) responsible for these effects remain poorly characterized. To quantify surface activity of soluble and insoluble CPs and their effects on lipid monolayers, a suite of surface specific linear and nonlinear optical methods and thermodynamic analyses were used to measure how CPs alter lipid monolayer organization, orientation, and compressibility at aqueous – air interfaces. Insoluble CPs remain physisorbed to aqueous surfaces, but surface tension data show that soluble CPs are also surface active with a limiting surface excess of 155 Å2/molecule. CP surface activity also manifests in 2nd order nonlinear optical measurements. Data from surface specific vibrational sum frequency generation experiments show that interactions between soluble CPs and lipid monolayers at the aqueous – air interface condense lipid monolayers, with high variability observed at lower CP concentrations. Soluble CPs increase lipid acyl chain ordering in 55Å2/molecule DPPC films at both very low CP concentrations and CP concentrations above 5 mg/ml. Such behavior is consistent with soluble CP aggregates occupying area at the aqueous – air interface, effectively compressing DPPC domains. Spectroscopic ellipsometry (SE) measurements reveal that these behaviors also affect the optical properties of a biological film with the most pronounced effects observed with low soluble CP concentrations.

Carbon particulate adsorption to aqueous – air interfaces and their effects on model biological membrane structure and organization

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.