Carbon dots synthesization via graphite laser ablation in biocompatible solution

Photoluminescent carbon dots (CDs) have been synthesized via laser ablation of graphite targets placed in biocompatible liquids. A Nd:YAG pulsed laser, 3 ns pulse duration, and 100 mJ pulse energy have been employed to irradiate graphite at a 1 Hz repetition rate in a phosphate-buffered saline (PBS) solution with water. The laser ablation yield was 77 ng/pulse, of which about 10% of the ablated mass is represented by synthesized CDs, Results demonstrated that the CDs dispersion is luminescent underUVexcitation light at 365 nm. At high laser fluence, of about 20 J/cm2, using a low spot size, the luminescence is due to a band in the blue region around about 475nm with a width of about 80 nm. Decreasing the laser fluence, by increasing the spot size, it is possible to change the luminescence emission band shifting it to the green-yellow or the red region. The luminescence depends on the type of solution used, the CDs concentration, pH value, temperature and others. The produced CDs dispersion finds interesting applications in biology and medicine as will be presented and discussed.