Tailoring phases of ferrihydrite/α-FeO@C nanocomposites using syringyl and guaiacyl-rich biomass-derived carbon nanodots for electrochemical application.

Biomass-derived carbon nanodots (CNDs) hold promise as effective reducing agents for metal oxide nanoparticles yet understanding the intricate interplay with CND structure remains challenging. This study explores the impact of lignin types, specifically syringyl (S), and guaiacyl (G) units in CNDs on metal oxide phases and their electrochemical activity toward dopamine oxidation. We design phases of ferrihydrite/α-FeO@C nanocomposites, using hazelnut carbon nanodots (HS-CNDs (S-rich)) and beetroot carbon nanodots (BS-CNDs (G-rich)) via a one-pot hydrothermal technique. Our findings show S units in HS-CNDs promote α-FeOOH/α-FeO@C, while G units in BS-CNDs favor α (β)-FeOOH/α-FeO@C. In contrast to α(β)-FeOOH/α-FeO@C, α-FeOOH/α-FeO@C exhibits superior electrochemical performance in dopamine oxidation due to its larger electrochemical active surface area, higher absorbance capacity, and shortened electron transfer length. Moreover, α-FeOOH/α-FeO@C nanocomposites demonstrate remarkable dopamine selectivity, achieving rapid detection response in 10 s with a low LOD of 4 nM within a broad linear range (0.05-0.3 μM), demonstrating impressive reproducibility (97.5 %), stability (96.4 %), and works in real-time human urine detection with a recovery rate of ranging from 94.57 % and 102.2 %. Therefore, the utilization of biomass-derived CNDs, particularly S and G units-rich CNDs, in tailoring the phases of ferrihydrite/α-FeO@C nanocomposites for electrochemical dopamine detection is promising.