  Surfaces (interfaces) dictate many physical and chemical properties of solid
materials and adsorbates considerably affect these properties. Nitrogen
molecules, which are the most abundant constituent in ambient air, are
considered to be inert. Our study combining atomic force microscopy (AFM),
X-ray photoemission spectroscopy (XPS), and thermal desorption spectroscopy
(TDS) revealed that nitrogen and water molecules can self-assemble into
two-dimensional domains, forming ordered stripe structures on graphitic
surfaces in both water and ambient air. The stripe structures of this study
were composed of approximately 90% and 10% water and nitrogen molecules,
respectively, and survived in ultra-high vacuum (UHV) conditions at
temperatures up to approximately 350 K. Because pure water molecules completely
desorb from graphitic surfaces in a UHV at temperatures lower than 200 K, our
results indicate that the incorporation of nitrogen molecules substantially
enhanced the stability of the crystalline water hydrogen bonding network.
Additional studies on interfacial gas hydrates can provide deeper insight into
the mechanisms underlying formation of gas hydrates.
