Luminescence enhancement of carbon dots synthesized by intense CW laser at 450 nm irradiating biocompatible solutions

Carbon dots (CDs) were synthesized by a continuum wave (CW) laser system irradiating vegetable charcoal placed in a Phosphate-Buffered Saline (PBS) solution. The laser operates at 450 nm with an output power of 50 W and 1 mm2 spot size, irradiating the carbon target for 1–3 h. The used charcoal consists of amorphous carbon that gives rise to CDs in liquids revealing high lumines- cence in the blue region. The formation of CDs is due to photo-thermal and photo-chemical effects induced by the prolonged laser irradiation inducing carbon atom ejection, scissions, radical formation, chemical bond breaking, molecular detachment bounded by weakened bonds and van de Walls forces, and nanoparticle functionalization in the used solution. The measurements have been concerned with the laser ablation yield, the Fourier Transmission Infrared (FTIR) spectroscopy, the UV-Vis optical spectroscopy, and the luminescence yield induced by UV excitation lamp at 365 nm wavelength. The main luminescence peak is observed at about 480 nm, characteristic of the blue color, with less significant involvement of the near regions at about 450 nm and 520 nm. Results suggest that CDs luminescence can be enhanced by the laser irradiation time, the PBS concentration, and the addition of acetic acid in the PBS solution. The presented luminescence in biocompatible solutions found many applications in different scientific fields. Overall, it is dis- cussed its application for bioimaging in the biomedical field.