Nanophase of Water in Nano-Diamond Gel

Abstract

The nanosized water phase has been discovered while studying differential scanning calorimetry (DSC) of the aqueous gel of nano-diamond particles (diameter ca. 5 nm). Two endothermic peaks were observed in the DSC traces of frozen gel upon warming; a broad peak appeared at 265 K before the melting of bulk water, which is attributed to the melting of nanophase water adsorbed onto the surface of nano-diamond particles. The events can be reproduced in exothermic fashion upon cooling the same sample. The mass of nanophase water per one nano-diamond particle and the melting enthalpy of nanophase water were derived from the DSC data. Similar nanophase water was observed earlier in gels prepared from an aqueous dispersion of C60 clusters with an average diameter of 68 nm, but the effect was not as distinct as with nano-diamond particles. These results demonstrate that DSC could be a versatile tool to study the stability of carbon nanoparticles in liquid media.