Facile surface functionalization of nanodiamonds.

Nanodiamonds (NDs) have versatile applications in electro-optical devices, sensors, and biomedicine. Owing to the difficulty in activation of the inert sp(3) C-H bonds on the surface of NDs, it is not trivial to modify the surface functionalities on NDs. A few functionalization methods have been reported in the literature for surface modification of NDs. Many of them, however, are either multiple steps/time-consuming, or require the use of highly toxic/environmentally unfriendly reagents, such as fluorine gas and sulfuric acid. It is necessary to develop a simple process for surface functionalization of NDs to have both hydrophobic and hydrophilic functional groups. In this report, a facile process was developed to allow easy and rapid surface modification of NDs to become dispersible in either water or organic solvents using the same process. The process involves surface graphitization of NDs, followed by radical initiated surface grafting of oligomers with various functionalities, including -C(=O)OCH(3), -COOH, -NH(2), or aliphatic moieties.