A Direct Probe of the Hydrogen Bond Network in Aqueous Glycerol Aerosols

Abstract

The properties of aerosols are of paramount importance in atmospheric chemistry and human health.The hydrogen bond network of glycerol-water aerosols generated from an aqueous solution with different mixing ratios, is probed directly with X-ray photoelectron spectroscopy. The carbon and oxygen X-ray spectra reveal contributions from gas and condensed phase components of the aerosol.It is shown that water suppresses glycerol evaporation up to a critical mixing ratio. A dielectric analysis using terahertz spectroscopy coupled with Infrared spectroscopy of the bulk solutions provides a picture of the microscopic heterogeneity prevalent in the hydrogen bond network when combined with the photoelectron spectroscopy analysis. The hydrogen bond network is comprised of three intertwined regions. At low concentrations, glycerol molecules are surrounded by water forming a solvated water network. Adding more glycerol leads to a confined water network, maximizing at 22 mol%, beyond which the aerosol resembles bulk glycerol. This microscopic view of hydrogen bonding networks holds promise in probing evaporation, diffusion dynamics and reactivity in aqueous aerosols.

Spectroscopic Fingerprints of Cavity Formation and Solute Insertion as a Measure of Hydration Entropic Loss and Enthalpic Gain

“…The THz spectrum of the solute and its hydration shell is obtained by subtracting the volume‐scaled absorption spectrum of bulk water from the absorption spectrum of a solution containing the solute of interest [27, 31] . Hydration‐shell vibrational spectroscopies provide valuable information on the intermolecular interactions involving the solute and its hydration water molecules [31, 35–37] . In our previous studies we focused on the HB intermolecular stretching region (100–300 cm −1 ), i.e.…”

Spectroscopic Fingerprints of Cavity Formation and Solute Insertion as a Measure of Hydration Entropic Loss and Enthalpic Gain

“…[27,31] Hydration-shell vibrational spectroscopies provide valuable information on the intermolecular interactions involving the solute and its hydration water molecules. [31,[35][36][37] In our previous studies we focused on the HB intermolecular stretching region (100-300 cm À 1 ), i.e. the low frequency region showing the collective vibrations of the water HBnetwork, and we were able to identify two characteristic bands of the HB-network in the alcohol hydration layer.…”

A Computational and Experimental View of Hydrogen Bonding in Glycerol Water Clusters

“…Recently, a molecular level picture of the hydrogen bond network was revealed using X-ray photoelectron spectroscopy of aqueous glycerol aerosols in conjunction with IR and THz spectroscopies of mixed solutions. 15 Therein, it was shown that upon increasing the glycerol content, the hydrogen bond network evolved from glycerol molecules being surrounded by water forming a solvated water network toward one where water is confined within glycerol's hydrogen bond network. Beyond a mole fraction of 22% glycerol, the aerosols resembled bulk glycerol.…”