Evaluating the influence of carbon quantum dots on starch-based bioplastics: Toward potential food packaging applications

Developing biodegradable food packaging films is crucial for reducing dependence on petroleum-based plastics. In this study, nitrogen-doped carbon quantum dots (CDs) were synthesized from citric acid and ethylenediamine via hydrothermal treatment and incorporated into sago starch films at concentrations of 0.5 %, 1 %, 3 %, and 4 % w/w of total solids using a solution casting method. The effects of CDs on structural, thermal, antioxidant, optical, and physicochemical properties were systematically investigated. CD addition enhanced the UV-shielding ability of the films. At 4 % CD content, UV transmittance decreased by 56.4 % (UV A ), 66.7 % (UV B ), and 73.9 % (UV C ) relative to the control film. CD incorporation also reduced moisture content from 31.25 % to 22.95 %, and increased the water contact angle from 37.1° to 67.7° at 3 % loading, indicating improved surface hydrophobicity. Structural characterization (FTIR, XRD) and imaging (SEM, TEM, AFM) confirmed successful synthesis, dispersion, and crystallinity improvement, although aggregation occurred at 4 %. The films also showed improved antioxidant activity and thermal stability. Overall, the integration of CDs at appropriate concentrations significantly enhanced the barrier, surface, and optical performance of sago starch films, demonstrating their potential as cost-effective, environmentally friendly packaging materials with added functionality. • Carbon quantum dots (CDs) were synthesized and incorporated into sago starch films. • CDs significantly enhanced UV-blocking, antioxidant activity, and hydrophobicity of the packaging films. • An optimal CD concentration (3 %) improved crystallinity, thermal stability, and surface morphology without aggregation. • The films showed reduced moisture content and increased water contact angle, improving barrier performance. • This study presents a low-cost, bio-based nanocomposite film with multifunctional properties for active food packaging.