Fluorescence Origin of Nanodiamonds

Abstract

Despite extensive work on the fluorescence behavior of graphite and graphene quantum dots, reports on the luminescence of nanodiamonds are so far much fewer. In fact, nanodiamonds are distinctly different from carbon quantum dots with nondiamond phases in both crystalline structure and electronic structure. Here, we report that fluorescent nanodiamond colloids exhibit strong visible fluorescence emissions and that their characteristics can be summarized as follows: (i) the fluorescence is unrelated to the size effect and (ii) obviously the excitation-dependent fluorescence, (iii) the maximum emission peak shows a giant red shift of 100 nm after heat treatment, and (iv) the red shift of fluorescence excited by a certain wavelength is out of sync with that of the strongest fluorescent peak. Based on these experimental observations above, the origin of nanodiamonds fluorescence is proposed to be the functional groups residing on the nanodiamonds, such as OH, ketone C═O, and ester C═O groups. These deductions...