Production of fluorescent nano-diamonds through femtosecond pulsed laser ablation

A one-step method for synthesizing nano-diamonds (NDs), femtosecond pulsed laser ablation, of bulk diamond in DI water is reported. The mean size of NDs is 3.0 nm observed by TEM. UV-Vis absorption spectrum reveals that there are two absorption peaks in NDs. For prepared NDs, it can be seen from emission spectrum that dual emission occurs under the excitation of either 260 nm or 280 nm, while the dual emission disappears after surface passivation. Moreover, the intensity of visible blue fluorescence emitted by NDs is significantly enhanced for passivated NDs. In addition, it is found that the ablation efficiency enhances with the increase of ablation power, which can be also verified by the intensity changing of UV-Vis absorption spectra. The maximum yield can reach to 8.2 mg·h−1 under 828 mW. These NDs emit stable blue emission and are synthesized by a rather simple green way, of which the NDs yield can meet the requirement of practical applications in terms of drug and gene delivery.