Nanodiamond as a possible carrier of extended red emission

Diamond nanocrystals (size similar to 100 nm) emit bright luminescence at 600-800 nm when exposed to green and yellow photons. The photoluminescence, arising from excitation of the nitrogen-vacancy defect centers created by proton-beam irradiation and thermal annealing, closely resembles the extended red emission ( ERE) bands observed in reflection nebulae and planetary nebulae. The central wavelength of the emission is similar to 700 nm, and it blueshifts to similar to 660 nm as the excitation wavelength decreases from 535 to 470 nm as the result of a combined excitation of two different detect centers [(N-V)(-) and (N-V)(0)]. Our observations lend support to the suggestion that nanodiamond is a possible carrier for the ERE band.