Green carbon dots synthesized from Chlorella Sorokiniana microalgae biochar for chrome detection.

[Display omitted] • The carbon dots (CDs) were efficiently synthesized from microalgae biomass biochar. • Carbon dots synthesis with different concentrations of KMnO 4 are compared. • CDs depolymerized with 8.54% and 10.0% KMnO 4 showed higher fluorescence intensity. • Fluorescence emitted by CDs was effectively quenched by Cr (VI) and Cr (III). • Detection for Cr (VI) and Cr (III) was performed between 0.01 and 100 mg.L⁻¹. In the quest to find an economical and accurate method of detecting toxic metals as well as finding an application for biochar as a fuel, this work used microalgae biochar to sinter Carbon Dots (CDs) that can be used as pathways for metallic ions detection. Carbon Dots from microalgae biochar (generated in pyrolysis) were synthesized through thermochemical depolymerization with KMnO 4 at different concentrations. After this step, the purification of the nanoparticles was performed. The characterization of CDs was performed through fluorescence intensity, Zeta Potential, Fourier Transform Infrared Spectroscopy (FTIR), and atomic force microscopy (AFM). The results showed that all samples exhibited fluorescence, samples synthesized with KMnO 4 at concentrations of 8.54 % and 10.0 % (CD-MBK06 and CD-MBK07, respectively) showed the highest fluorescence intensity and good stability. When adding Cr (VI) and Cr (III) to the CD-MBK06 and CD-MBK07 samples, it is possible to notice that there was fluorescence quenching as the metal ion concentration increased, except for the CD-MBK07 sample for Cr (III), at a length of 350 nm, indicating that this sample shows selectivity for extinction only for Cr (VI). [ABSTRACT FROM AUTHOR]