Chemical modification of the diamond surface using benzoyl peroxide and dicarboxylic acids

We report a new method for introducing carboxylic groups onto the diamond surface. Hydrogenated diamond surfaces were treated in a solvent containing benzoyl peroxide and dicarboxylic acid. Surface characterization was performed by diffuse reflectance infrared Fourier transform transform spectroscopy. After the reaction, a C=O peak appeared, and the shape of the C-H peak at 2780-2960 cm^-1 depended on the kind of dicarboxylic acid. When deuterium-labeled diamond powders were treated in the same manner, aliphatic C-H peaks were observed in the range 2780-2960 cm^-1. The C-H peaks were assigned to the -(CH₂)_n-groups of the dicarboxylic acids bonding to the diamond surface. When the modified diamond surfaces were treated with NaOH(aq), peaks assigned to the C=O bond of the -COONa groups appeared at 1578 cm^-1, which indicated that carboxylic groups were present on the diamond surface. The presence of HOOC- (CH₂)_n-OCO- groups on the diamond surface has been demonstrated.