Abstract: Atmospheric and man-made droplet aerosols show many commonalities in their physical and chemical properties.  Both systems are characterized by confinement and large surface to volume ratio, which alter the chemistry of many processes relative to their bulk solution counterparts. I will illustrate the observed complexity of behavior of single and multiple (macro)ions in nano- and micro- droplets using examples of electrostatic confinement [1], supercooling [2], Rayleigh jets,  pearl-necklace and``star''-shaped formations [3], and extrusion of macromolecules from droplets [4]. Aerosols comprise a broad range of droplet sizes that vary from the nano to macro scale.  Scaling laws, continuum modeling, solution of non-linear Poisson-Boltzmann equation in spherical geometry [5], and atomistic modeling assist us in finding how electrostatic properties, pH [5], and composition changes with droplet size.  It will be demonstrated how the relation of these properties, pH, and composition between the nano and micro systems allows us to decode the steps in electrospray ionization mechanism and obtain insight into the charging mechanisms of proteins.  Applications of these studies are also found in electrospinning, ink-jet printing, and even in certain quantum mechanical phenomena such as stability of semiconducting vortices [6], and of multielectron He bubbles within superfluid He [7].

References

1. Kwan, V., Maiti, S. R., Saika-Voivod, I., & Consta, S. (2022).  Salt enrichment and dynamics in the interface of supercooled aqueous droplets. JACS, 144, 11148-11158.

2. Malek, S. M., Kwan, V., Saika-Voivod, I., & Consta, S. (2021). Low density interior in supercooled aqueous nanodroplets expels ions to the subsurface. JACS, 143, 13113-13123.

3. Oh, M. I., & Consta, S. (2017). Stability of a transient protein complex in a charged aqueous droplet with variable pH. JPCL, 8, 80-85.

4. Consta, S., & Malevanets, A. (2012). Manifestations of charge induced instability in droplets effected by charged macromolecules. PRL, 109, 148301.

5. Malevanets, A., & Consta, S. (2013). Variation of droplet acidity during evaporation. JCP, 138(18), 184312.

6. Lukyanchuk, I., Vinokur, V. M., Rydh, A., et al. (2015). Rayleigh instability of confined vortex droplets in critical superconductors. Nature Physics, 11, 21-25.

7. Moroshkin, P., Leiderer, P., Möller, T. B., & Kono, K. (2017). Taylor cone and electrospraying at a free surface of superfluid helium charged from below. Physical Review E, 95, 053110.