Raman fingerprints of ultrasmall nanodiamonds produced from adamantane

The synthesis of ultrasmall (2-5 nm) nanodiamonds purely from adamantane at pressure of 12 GPa is reported. Their structural features have been studied by Raman spectroscopy. The unusual vibration band containing a number of pronounced maxima at about 1147, 1245, 1344, and 1456 cm-1 was detected in Raman spectra. The band is confidently identified with the bending vibrational modes of CHx groups terminating the nanodiamonds surface. Excessively intense mode at 1344 cm-1 is explained by its coupling with the 1328 cm-1 diamond phonons. The Raman band found is proposed to be used for express recognition of ultrasmall nanodiamonds produced from adamantane and other hydrocarbons with a high hydrogen content. Moreover, polarized CH bonds on a diamond surface are sensitive to environmental conditions. This opens up opportunities for using the diamond produced from adamantane as ultrasmall nanosensors in biology, chemistry, and medicine