Structure of Single Aqueous MgSO4 Droplets Ultrasonically Levitated in the Air: Supersaturation and Crystallization

• Published in: Journal of solution chemistry 2024-05, Vol.53 (5), p.610-625
• Main Authors: Yamaguchi, Toshio, Matsuo, Shun-ichiro, Yoshida, Koji, Kurisaki, Tsutomu, Ishizaka, Shoji, Ohara, Koji
• Format: Article
• Language: English
• Subjects: Aerosols; Banded structure; Chemistry; Chemistry and Materials Science; Composition; Condensed Matter Physics; Coordination numbers; Correlation; Crystallization; Droplets; Geochemistry; Hydrates; Industrial Chemistry/Chemical Engineering; Inorganic Chemistry; Magnesium sulfate; Molecular structure; Oceanography; Physical Chemistry; Raman spectra; Solvation; Speciation; Supersaturation; Synchrotron radiation; X-ray scattering
• ISSN: 0095-9782; 1572-8927
• DOI: 10.1007/s10953-023-01309-9

Aerosol droplets are fully involved in forming clouds and play a critical role in global climate change. The investigation of the properties, speciation, and structure of aerosol droplets at a molecular level is highly needed for understanding the physicochemical behaviors and processes of aerosol droplets. We investigate the composition, speciation, and structure of a single aqueous MgSO 4 droplet of 1 mm size ultrasonically levitated in the air and bulk solutions under ambient conditions by in situ Raman and synchrotron X-ray scattering. The composition and speciation are determined by measuring Raman spectra of the sulfate ion’s S–O band and water’s O–H bands. The X-ray data are subjected to empirical potential structure refinement modeling to extract the site–site pair correlation function, coordination number distribution, and 3-D structure for the ion solvation, association, and solvent water. In situ X-ray scattering measurements observe the crystallization of MgSO 4 hydrates from a droplet.