Introduction of molecules containing a NO2 group on diamond surface by using radical reaction in liquid phase

Chemical reaction of hydrogenated diamond surface with nitrobenzoic acid (NO2-C6H4-COOH) and the radical species was investigated. The IR peak assigned to the NO2 group appeared after the reaction process. The peak intensity of the NO2 group depended on the steric structure of the reacted nitrobenzoic acid. The NO2 peak intensity of the diamond reacted with p-nitrobenzoic acid is much smaller than that of the diamond reacted with o-, or m-nitrobenzoic acid. In this study, 3,4-dinitorobenzoic acid or 3,5-dinitorobenzoic acid was also used. The IR spectra for the diamond treated with 3,4-dinitorobenzoic acid were unclear. On the other hand, the IR spectra for the diamond treated with 3,5-dinitorobenzoic acid showed the peak assigned to the NO2 group. From the experimental results, we may assume that the NO2 group at para-position against the COOH group hindered the reaction of the COOH group with diamond surface. The NO2 peak intensity for the diamond treated with 3,5-dinitorobenzoic acid was comparable with that for the diamond treated with o- or m-nitrobenzoic acid. These results should means that the amount of the NO2 group introduced on diamond surface was comparable. The introduction of NO2 group on diamond surface was realized by the method applied in this study.