Nanodiamond as a Possible Carrier of Extended Red Emission

Diamond nanocrystals (size ~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 ~700 nm, and it blueshifts 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.