Biosynthesis of Doped Carbon Dots-Decorated MnO₂ Nanocomposites Using Eucalyptus Extract: Evaluation of Catalytic Activity

In the present work, biosynthesis of two nanocomposites (NC1 and NC2) with different dopants (boron or sulfur) was carried out by utilizing secondary metabolites of Eucalyptus citriodora leaf extract for degradation studies of cationic and anionic dyes. Biosynthesized nanocomposites were characterized by UV–Vis spectroscopy, FTIR spectroscopy, SEM imaging, and EDX spectra, which confirmed their functional groups, uniform structure, and the presence of desired dopants. Optimum response for crystal violet dye was observed with 2 mL and 1.5 mL volume, in alkaline medium (pH = 8) at room temperature with dye concentration = 5 mg/L within time interval of 60 and 45 min for NC1 and NC2, while eriochrome black T has shown maximum degradation at 1.5 mL and 1 mL volume in acidic medium at room temperature with 5 mg/L dye concentration in time period of 90 and 60 min for NC1 and NC2. Interference and radical scavenging experiment was performed to elaborate the efficiency and working mechanism of nanocatalysts. The proposed mechanism regarding nanoparticles formation was also discussed.