Fig. 7

Raman spectra of the 25- and 2–5-nm nanodiamond under a 50 GPa pressure. Excitation wavelength is 458 nm. An initial 25-nm nanodiamond band 1329 cm⁻¹ shifted to 1483 cm⁻¹ exactly in accordance with the pressure dependence (2) of Raman mode of diamond with the bulk modulus 443 GPa. An additional band of the 25-nm nanodiamond around 1800 cm⁻¹ showed a typical behavior for a G band of sp²-bonded carbon: disappearance of this band under pressure of 50 GPa