Chemical modification of diamond surface with linoleic acid by using benzoyl peroxide

In this study, the introduction of the C=C bond, which is known to be chemically active, on diamond surface was attempted using a reaction with unsaturated fatty acid. The chemical reactivity of a hydrogenated diamond surface with linoleic acid, which was most effective for introducing of the C=C bond, using benzoyl peroxide was investigated in detail. The diamond surface modified with the C=C bond was used as the substrate for the surface-modified diamond. Different radical source such as NCS, NBS, AIBN, and TEMPO were allowed to react with the diamond surface treated with linoleic acid. After the reaction with NCS, NBS, or AIBN, IR peaks at 3011 cm− 1, which correspond to the C–H bond on the C=C bond, significantly decreased in size, and XPS spectra showed that the elements that derived from the reacted radical source, that is Cl, Br, or N, existed on the diamond surface. On the other hand, after the reaction with TEMPO no XPS peak of the N atoms appeared although the IR peak at 3011 cm− 1 slightly decreased. These experimental results indicate that the C=C bond introduced on diamond surface can participate in chemical reaction. The method used in this study could become a very useful technique if the coverage factor of the C=C bond is improved by optimization of the reaction condition.

Research Highlights
► The C=C bond, which is known to be chemically active, was introduced on diamond surface by using a radical reaction with unsaturated fatty acid.
► The reaction of hydrogenated diamond surface with linoleic acid was most effective for introducing of the C=C bond when benzoyl peroxide was used as radical initiator.
► After the reaction with NCS, NBS, or AIBN, XPS spectra showed that the elements that derived from the reacted radical source, that is Cl, Br, or N, existed on the diamond surface.