Herein, nitrogen-doped carbon dots (N-CDs) were synthesized by hydrothermal carbonization of Mexican duckweed (Lemna minor) biomass as a sustainable carbon precursor, using lysine and arginine as molecular nitrogen sources to tailor the surface chemistry. FTIR spectroscopy revealed the formation of C=N and C ¿ N functional groups, while XPS confirmed a significant increase in nitrogen incorporation following amino acid-assisted synthesis. High-resolution N 1 s deconvolution demonstrated that the molecular structure of the nitrogen precursor governs the relative distribution of graphitic, pyridinic, and pyrrolic nitrogen species. In particular, arginine-derived N-CDs exhibited a higher contribution of pyrrolic nitrogen, whereas lysine promoted a greater proportion of graphitic nitrogen. These differences in nitrogen configuration were accompanied by changes in the optical and photoluminescent properties of the N-CDs. Consequently, arginine-derived N-CDs exhibited the highest antibacterial activity against Escherichia coli, which correlated with their distinct nitrogen configuration and modified optical properties. Overall, the results demonstrate that molecular precursor engineering is an effective strategy for modulating nitrogen configurations in biomass-derived carbon dots, thereby establishing structure¿property relationships that inform the rational design of sustainable antimicrobial carbon nanomaterials with improved antibacterial performance associated with precursor-dependent nitrogen speciation.
