Waste-derived nitrogen-doped carbon dots for sustainable PVA nanocomposites with enhanced optoelectronic properties

Sustainable nanomaterials with enhanced optoelectronic properties are essential for advancing green technologies. Here, we present a green strategy for fabricating polyvinyl alcohol (PVA) nanocomposites with improved optoelectronic performance by incorporating nitrogen-doped carbon dots (N-CDs) synthesized hydrothermally from eggplant peel waste (EPPW). The N-CDs exhibited a mean size of 1.88 nm, a quantum yield of 2.82 %, and distinct absorption peaks at 245 nm (π–π ⁎ transitions of aromatic sp 2 -hybridized carbon domains) and 283 nm (n–π ⁎ transitions of C O groups). Incorporation of N-CDs into the PVA matrix induced significant optical and structural modifications, extending light absorption to 440 nm, reducing the optical band gap from 6.29 to 3.18 eV, and increasing the Urbach energy from 0.486 to 0.532 eV. The crystallinity decreased from 31.65 % to 21.33 %, while the dielectric constant (ε₁) increased to 3.48 × 10 −3 , and the phase velocity rose to 2.60 × 10 8 m/s with a corresponding reduction in the refractive index. These results, confirmed by FTIR, XPS, UV–Vis, PL, 1 H NMR, 13 C NMR, HR-TEM, and XRD analyses, demonstrate that waste-derived N-CDs serve as efficient and sustainable nanofillers for tuning the electronic structure of PVA, making them highly promising for UV-shielding and flexible optoelectronic applications.