Wenwu Xu http://orcid.org/0000-0002-0651-9562
Joseph S. Francisco http://orcid.org/0000-0002-5461-1486
Xiao Cheng Zeng http://orcid.org/0000-0003-4672-8585
Date of this Version
NATURE COMMUNICATIONS (2021) 12:5602
It is well known that NaCl salt crystals can easily dissolve in dilute aqueous solutions at room temperature. Herein, we reported the first computational evidence of a novel salt nucleation behavior at room temperature, i.e., the spontaneous formation of two-dimensional (2D) alkali chloride crystalline/non-crystalline nanostructures in dilute aqueous solution under nanoscale confinement. Microsecond-scale classical molecular dynamics (MD) simulations showed that NaCl or LiCl, initially fully dissolved in confined water, can spontaneously nucleate into 2D monolayer nanostructures with either ordered or disordered morphologies. Notably, the NaCl nanostructures exhibited a 2D crystalline square-unit pattern, whereas the LiCl nanostructures adopted non-crystalline 2D hexagonal ring and/or zigzag chain patterns. These structural patterns appeared to be quite generic, regardless of the water and ion models used in the MD simulations. The generic patterns formed by 2D monolayer NaCl and LiCl nanostructures were also confirmed by ab initio MD simulations. The formation of 2D salt structures in dilute aqueous solution at room temperature is counterintuitive. Free energy calculations indicated that the unexpected spontaneous salt nucleation behavior can be attributed to the nanoscale confinement and strongly compressed hydration shells of ions.
Supplementary files, including 6 movies, attached below.
Zhao NC 2021 SUPPL 2.pdf (7 kB)
Description of additional supplements
Zhao NC 2021 SUPPL movie 1.mp4 (12411 kB)
Zhao NC 2021 SUPPL movie 2.mp4 (11931 kB)
Zhao NC 2021 SUPPL movie 3.mp4 (29829 kB)
Zhao NC 2021 SUPPL movie 4.mp4 (29248 kB)
Zhao NC 2021 SUPPL movie 5.mp4 (12365 kB)
Zhao NC 2021 SUPPL movie 6.mp4 (22075 kB)