Whereas, common aqueous solutions (e.g. NaCl) conduct some electricity, pure water is a perfect insulator. Speculations about the transformation of water into a metallic state are not new. However, it has been calculated, that the required pressures could only be achieved within the cores of large planets. For alkali metal-liquid ammonia solutions a gradual transition from an electrolyte solution (blue) to a metallic solution (bronze) is well known, if the concentration of dissolved alkali metal is increased. Unfortunately, the corresponding experiment with water and alkali metal is not possible, as their reaction is quite vigorous. The explosive reaction is initiated by the ultrafast release of electrons from the alkali metal to water leading to a massive positively charged metal surface, which then lead to a coulomb explosion. Nevertheless, we found a way to avoid the explosive behavior by condensing water on the surface of a NaK droplet. First, the fascinating golden liquid was observed by naked eye in lab. Later, we used UV/Vis spectroscopy as well as x-ray photoelectron spectroscopy (PES) to quantify its properties. Indeed, both techniques revealed a plasmon frequency around 2.7 eV (450 nm). Additionally, we detected a small Fermi edge in the PES spectrum. The width of the conduction band and the position of the plasmon frequency are in well agreement of the free electron model. These two fingerprints are characteristic for metals. We not only demonstrate that metallic water solutions can actually be prepared in lab, but also characterizes its spectroscopic properties connected with its beautiful golden metallic sheen.

Metallic water solutions

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.