Surface modification to improve hydrophobicity of detonation nanodiamond.

In this work, surface treatment of nanodiamonds (NDs) produced by a detonation technique has been conducted using oleic acid and dodecylamine in order to achieve a stable dispersion in oil. From Fourier transform infrared spectroscopy (FTIR) analyses, it was found that the NDs have various surface functional groups such as -NH2, -COOH, -OH, etc. By inducing covalent bonding between the carboxyl group of oleic acid and the amine group of the ND surface with high chemical reactivity, NDs were well-dispersed in oil for a lengthy period of time. High resolution transmission electron microscopy (HRTEM) images indicate that the surface treatment with oleic acid is highly effective in breaking down the aggregates of NDs into smaller sized particles. The dispersion stabilities of the oils containing as-received NDs and surface treated NDs were compared to each other using Turbiscan measurement.