Surface reforming of the oxidized diamond surface with silane coupling reagents

Diamond surface reforming was carried out using various silane coupling reagents (n-octyltrimethoxysilane, 3-aminopropyltrimethoxysilane, or 3-mercaptopropyltrimethoxysilane). In order to introduce the O-H group, which reacts with the methoxy group in the silane coupling reagents, on the diamond surface, hydrogenated diamond surfaces were treated with mineral acids (H₂SO₄, H₂SO₄ + HNO₃, or aqua regia). The diamond powders treated with H₂SO₄ or H₂SO₄ + HNO₃ were utilized as the diamond substrate for the reaction with the silane coupling reagents. After the treatment with the silane coupling reagents, peaks assigned to the chemical bonds in the silane coupling reagents appeared in the IR spectrum of the diamond powders. Moreover, these peaks remained even after washing 3 times with organic solvents. The oxidized diamond surface was changed from hydrophilic to hydrophobic upon treatment with n-oetyltrimethoxysilane. From the results of this study, it was confirmed that the silane coupling reagent is effective for the surface reforming of diamond treated with mineral acid.