Antioxidant Performance and Characterization Comparison of Carbon Dots Derived from Agricultural Waste Pineapple Peel

This study prepared carbon dots (CDs) from agricultural waste pineapple peel via an eco-friendly microwave method, optimizing their performance through copper ion and chitosan doping. Multiple characterization techniques and performance tests were employed for systematic analysis. Antioxidant assays revealed that PP-CDs have excellent concentration-dependent free radical scavenging activity: the DPPH IC₅₀ values of Pineapple Peel Carbon Dots (PP-CDs), Copper-Doped Pineapple Peel Carbon Dots (Cu-PP-CDs) and Chitosan-Doped Pineapple Peel Carbon Dots (CS-PP-CDs) are 0.79, 0.95 and 0.98 mg/mL, while their ABTS IC₅₀ values are 0.22, 0.40 and 0.26 mg/mL, respectively. Antibacterial tests showed modified CDs have enhanced activity: Cu-PP-CDs exhibit inhibition zones of 23.1 ± 0.13 mm (<i>E. coli</i>) and 17.3 ± 0.05 mm (<i>S. aureus</i>) with MICs of 2.5 and 5.0 mg/mL, while CS-PP-CDs have respective zones of 12.8 ± 0.08 mm and 16.3 ± 0.12 mm with a 5.0 mg/mL MIC for both strains. All CDs present a quasi-spherical morphology and emit yellow fluorescence under UV excitation, with PP-CDs showing the strongest intensity. This study provides technical support for high-value utilization of pineapple peel and development of multifunctional CDs, which have food field potential but face large-scale production and toxicological evaluation challenges.