Single-step preparation of fluorescent carbon nanoparticles, and their application as a fluorometric probe for quercetin

We report on a method for the determination of quercetin based on the quenching of the fluorescence of carbon nanoparticles (CNPs). The CNPs were prepared by carefully adding an aqueous solution of glucose to solid diphosphorus pentoxide. This single-step method proceeds rapidly and gives large quantities of CNPs. Neither high temperatures nor complicated synthesis steps are needed. The resulting CNPs have an average size of 120 nm and were characterized by high-resolution TEM, FT-IR, elemental analysis and spectrofluorometry. The fluorescence of the CNPs decreases with increasing concentrations of the flavonoid quercetin, with a linear response to quercetin in the 3.3 to 41.2 μM concentration range in pH 6.0 water solution and also in a solution containing 16 % (v/v) of fetal bovine serum. The detection limit is as low as 0.175 μM, and the Stern-Volmer quenching constant is 4.34 × 10⁴ M⁻¹. (author)