Visible fluorescence in carbon dots deposited on silicon under energetic proton beams excitation

Carbon dots (CDs) have been obtained by laser ablation of charcoal in a biocompatible liquid and deposited as a thin film on a silicon substrate. A ns-pulsed Nd:YAG laser, operating at 1064 nm of wavelength, irradiates for times up to 3 h the solid carbon target placed into a phosphate-buffered saline (PBS) solution and distilled water, to prepare the CDs dispersion. The prepared thin film on silicon, under a UV lamp at 365 nm in air generates fluorescence in the visible region, with a band around 470 nm, with a blue color. Further investigations concern the thin-film irradiation using 0.8–3.0 MeV protons with 3 nA current in a vacuum, showing also fluorescence in the visible region, from about 400 up to 700 nm, as recorded by a suitable optical spectrometer. The practical applications of CDs are also presented especially in the biomedical field and in the dosimetry ambit, where they can be employed for bioimaging, diagnostics, and therapy.