Carbon quantum dots synthesis by laser ablation of graphene oxide in biocompatible solutions

A biocompatible dispersion of carbon quantum dots (CQDs) has been obtained by laser irradiation of graphene oxide (GO) in liquid media. The CQD synthesis uses a pulsed IR laser operating at 970 nm, with a 100 ms pulse duration and a fluence of 1.1 kJ/cm2. The carbon target consists of GO sheets containing micrometric GO flakes, immersed in standard phosphate-buffered saline (PBS) solution used in biology. CQDs are functionalised with solution salts and, under UV excitation, produce high-intensity dispersion luminescence in the visible region. The optical properties and other physical characteristics of the dispersions are presented. The CQDs’ fluorescent emission occurs in the blue region, around 478 nm, upon excitation at 365 nm. This study provides an inexpensive and simple method for synthesising biocompatible CQDs in liquids for useful applications in bioimaging, diagnostics, and therapy.