1：Experimental Design and Method Selection:

The study involved synthesizing CNDs via microwave irradiation using glucosamine hydrochloride as a precursor. Carboxyl groups were blocked using EDC/NHS coupling, and amino groups were blocked using citraconic anhydride. Antioxidant activity was evaluated using UV-Vis spectroscopy and electrochemical assays with DPPH? as the radical.

2：Sample Selection and Data Sources:

CNDs were synthesized and modified. DPPH? in methanol was used as the radical source. Samples included unmodified, –COOH-blocked, and –NH2-blocked CNDs.

3：List of Experimental Equipment and Materials:

Microwave synthesizer (908005 Microwave Reactor Discovery System, CEM Corp), glucosamine hydrochloride (Alfa Aesar), EDC (TCI), NHS (Aldrich), citraconic anhydride (Aldrich), DPPH? (Alfa Aesar), methanol (Fisher Scientific), AFM (5600LS AFM, Agilent Technologies), EDX (S-4800-I FESEM w/Backscattered Detector, Carl Zeiss), FTIR (Varian 670, Agilent Technologies), Raman (XploRA One Raman Confocal System, Horiba), XPS (ESCALAB 250 Xi, Thermo Fisher), XRD (Agilent Technologies Oxford Gemini), NMR (Agilent 700 MHz NMR, Agilent Technologies), UV-Vis (Cary 6000i, Varian, Agilent Technologies), fluorescence spectrometer (Fluoro-Max 4 fluorometer, Horiba), electrochemical cell with gold working electrode, Ag/AgCl reference electrode, and platinum counter electrode (Fisher Scientific).

4：Experimental Procedures and Operational Workflow:

CNDs were synthesized by microwave heating, purified by centrifugation and dialysis, and freeze-dried. Blocking reactions were performed with EDC/NHS or citraconic anhydride, followed by dialysis and freeze-drying. Antioxidant activity was measured by mixing CNDs with DPPH? in methanol, incubating in the dark, and measuring absorbance at 517 nm or performing cyclic voltammetry.

5：Data Analysis Methods:

Antioxidant activity was calculated from UV-Vis absorbance changes. Electrochemical data were analyzed using the Randles-Sevcik equation to determine diffusion coefficients and scavenging activities. Statistical analysis included means and standard deviations from multiple trials.