The genesis of an ice sample matters!

We performed laboratory experiments to examine the relationship between the technique of preparing a frozen sample; its morphology; and chemical speciation. The luminescence of aromatic compounds (naphthalene, methylnaphthalene, anthracene) was utilized to learn about the extent of the compounds’ aggregation.

In aqueous solutions, the cooling rate determines the morphology of the resulting ice samples (analyzed with an environmental scanning microscope), (Vetráková, Neděla et al. 2019) the extent of the solute crystallization, and the plasticity of the freeze-concentrated solution (FCS) glass formed in the veins in between the ice crystals. Faster cooling allows higher degree of hydration of the aromatic compounds in the FCS. Conversely, vapor deposition of naphthalene on ice at 253 K results in microscopic naphthalene crystals, suggesting molecular mobility on the surface layer of ice at atmospherically relevant temperatures. (Ondrušková, Krausko et al. 2018) Surface acidity was proved via sulfonephthalein dyes, finding strong dependence on the salts present.(Imrichova, Vesely et al. 2019)

Our results connect the freezing methods and sample history with the compounds’ chemical identity in ice.

 

 

Imrichova, K., L. Vesely, T. M. Gasser, T. Loerting, V. Nedela and D. Heger (2019). "Vitrification and increase of basicity in between ice Ih crystals in rapidly frozen dilute NaCl aqueous solutions." J Chem Phys 151(1): 014503.

Ondrušková, G., J. Krausko, J. N. Stern, A. Hauptmann, T. Loerting and D. Heger (2018). "Distinct Speciation of Naphthalene Vapor Deposited on Ice Surfaces at 253 or 77 K: Formation of Submicrometer-Sized Crystals or an Amorphous Layer." The Journal of Physical Chemistry C 122(22): 11945-11953.

Vetráková, Ľ., V. Neděla, J. Runštuk and D. Heger (2019). "The morphology of ice and liquid brine in an environmental scanning electron microscope: a study of the freezing methods." The Cryosphere 13(9): 2385-2405.