Chemical reaction of hydrogenated diamond surface with amino acids by using N-chlorosuccinimide

Various organic compounds can be immobilized on a diamond surface if a chemically active organic functional group, such as an NH2 group, is introduced on the diamond surface. We therefore attempted to introduce an NH2 group on a diamond surface by using chemical reaction of a hydrogenated diamond surface with an amino acid and NCS (N-chlorosuccinimide). From our previous experimental results (Diamond Relat. Mater., 15, 668 (2006)), we expected that a functional group could be introduced on the diamond surface. However, there was no peak assigned to the NH2 group in the IR spectra for diamond powder treated with amino acids. The diamond powder treated with L-serine, L(−)-threonine, L(−)-phenylalanine, L(+)-arginine, L-histidine, or L-asparagine monohydrate had a specific peak at 2275 cm− 1 in the IR spectra. Moreover, the diamond powder treated with L(−)-threonine had the highest intensity of the peak at 2275 cm− 1. Therefore, the chemical reaction of a hydrogenated diamond surface with L(−)-threonine was further examined in detail. Unfortunately, the assignment of the peak at 2275 cm− 1 was unclear. However, we speculate from the compounds in the chemical reaction process that the peak is assigned to the CN group, although the peak position is slightly different from that of the normal CN group.