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 energy, 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 fluorescence 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. •Albumin-like proteins have been reported as a good biomass precursor for FC-NPs.•FC-NPs were synthesized at room temperature by using bovine serum albumin as the primary biomass source.•Alkali conditions and the addition of glutaraldehyde help in the direct formation of FC-NPs.•BSA FC-NPs reach fluorescence quantum yields up to 27 %.