Hydrophobic/lipophilic nanodiamond particles fabricated by surface modification with 1‐octadecene

Abstract

The surface of nanodiamond (ND) particles was modified with 1‐octadecene via a simple thermal reaction to obtain octadecyl‐modified ND. Fourier transform infrared spectroscopy and thermogravimetric analysis results indicated that octadecyl groups were successfully introduced onto the ND surface. The amount of the octadecyl groups on the ND surface was observed to increase with increasing reaction time and to eventually saturate. A bead‐milling process, which enabled disaggregation of NDs in 1‐octadecene, was observed to increase the amount of octadecyl groups adsorbed onto the ND surface. The estimated surface coverage was as high as 2.2 × 1014 molecules cm−2, which corresponds to submonolayer level. Dispersion tests revealed that the octadecyl‐modified ND particles exhibit hydrophobic/lipophilic character, whereas the oxidized ND (before surface modification with 1‐octadecene) exhibited good dispersibility in water. Particle size distribution analysis by dynamic light scattering revealed that the particle size of the octadecyl‐modified ND in chloroform, a non‐polar solvent, was ca. 20 nm. Thus, the present method should be useful for fabricating NDs that can be dispersed in non‐polar organic solvents and should facilitate the expansion of the application fields of ND.