One-pot room-temperature direct synthesis of bovine serum albumin-based fluorescent carbon nanoparticles

Fluorescent carbon nanoparticles (FC-NPs) with a mean size of 5.5 nm were fabricated at room temperature by means of a novel one-pot direct synthesis method, using bovine serum albumin (BSA), as a biomass-based precursor, and glutaraldehyde in a mixture of water/ethanol (1:4 v/v) under alkali conditions. This novel method shortens the times of synthesis and purification of the nanoparticles, and does not require thermal en-ergy, since no calcination is needed for the nanoparticles production, and the waste of reactants and solvents is minor. The FC-NPs displayed two emission peaks: one around 450 nm, and the second at 555 nm, being the later the most intense for wavelength excitations from 450 nm; fluorescence quantum yields values varied from 11.6 to 27 %, depending on their synthesis conditions, and in fact, the solutions emit a strong green-yellow fluo-rescence when excited with 532 nm. The FTIR spectra indicated that the main functional groups present were-NH2 and-COOH. XPS analysis confirmed the FTIR results and showed that carbon dots were composed mainly of C, N, O and Na. Finally, we tested the fluorescent carbon nanoparticles as cell biomarkers in human, plant cell lines and microbial cultures, achieving good results for this application.