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[Display omitted] • A nontoxic metal-free carbon dot/g-C 3 N 4 composite photosensitizer was fabricated. • Novel visible-light-driven antimicrobial films were successfully constructed. • Incorporated carbon dot/g-C 3 N 4 improved the physicochemical properties of the films. • The "fresh-like" characteristics of bananas were effectively maintained. A novel carbon dot/g-C 3 N 4 nanocomposite (CCN) exhibiting enhanced photocatalytic activity was developed and used as a photoactive nanofiller to construct corn starch/carboxymethyl cellulose (CS/CMC)-based functional films. The morphologies and structures of the CCN-CS/CMC composite films were investigated with scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. The effects of the CCN on the physicochemical properties and antibacterial activities of the films were analyzed. The properties of the films were optimized with the addition of CCN (0.20 mg/mL), and the tensile strength of the film was increased to 11.9 MPa and the water contact angle was increased to 103.39°. The optimal active film showed > 99.9 % antibacterial efficiencies against Escherichia coli and Staphylococcus aureus under visible light and prolonged the shelf lives of bananas for more than four days compared to the 4-day shelf life of the control. This work provides a novel route for developing antimicrobial active packaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • The resource conversion of citrus peel (CP) biowaste was effectively realized. • A novel metal- and additive-free CP-derived CDs/g-C 3 N 4 composites were synthesized. • CP-derived CDs/g-C 3 N 4 showed enhanced photodegradation performance for SY removal. • The photodecomposition method exhibited excellent reusability and biosafety. In this study, novel, metal-free, CP-derived CDs/g-C 3 N 4 nanocomposites (CDCNs) were created by introducing citrus peel-derived carbon dots (CP-derived CDs) into graphite carbon nitride (g-C 3 N 4) by a green hydrothermal method. The CDCNs were revealed to have superior photoelectrochemical properties relative to pristine g-C 3 N 4 for the photocatalytic degradation of the food dye sunset yellow (SY) under visible light. For SY decomposition, the recommended catalyst contributed almost 96.3% to the photodegradation rate after 60 min of irradiation, showing satisfactory reusability, structural stability and biocompatibility. Moreover, a mechanism for enhanced photocatalytic SY degradation was proposed according to band analysis, free radical trapping and electron paramagnetic resonance (EPR) results. A possible pathway for SY photodegradation was also predicted from UV–visible (UV–Vis) spectroscopy and high-performance liquid chromatography (HPLC) results. The constructed nonmetallic nanophotocatalysts afford a novel route for the elimination of harmful dyes and for the resource conversion of citrus peels. [ABSTRACT FROM AUTHOR]