Fluorescent poly(vinyl alcohol) (PVA) composite films incorporating heteroatom-doped carbon dots (CDs) were developed for heavy metal sensing and packaging applications in the food industry. Uniformly dispersed nitrogen-doped (N-doped), fluorine and nitrogen codoped (F–N-doped), and sulfur and nitrogen codoped (S–N-doped) CDs retained strong photoluminescence in the PVA composite films, with their emission characteristics tuned through heteroatom doping. Mechanical characterization revealed that the N-doped film exhibited the highest elastic modulus across films, whereas the S–N-doped film demonstrated enhanced compliance and elongation. Wide-angle X-ray scattering confirmed homogeneous nanoparticle distribution and the promotion of tensile stress via chain realignment. Ion sensing studies highlighted dopant-dependent selectivity, with the S–N-doped film exhibiting the broadest sensitivity enhancement across films, achieved limits of detection of 0.4561, 0.4937, 0.6557, and 0.6817 ppm for cobalt(II), iron(II), copper(II), and nickel(II), respectively. The incorporation of S–N-doped CDs yielded a film with a more porous, uniform morphology and improved ductility, facilitating analyte diffusion and contributing to superior heavy metal ion sensing performance. X-ray absorption near-edge structure measurements confirmed dominant first-shell metal–O coordination upon adsorption. Overall, the S–N-doped film offered the best balance between mechanical robustness and fluorescence, demonstrating its potential as a candidate material for reliable heavy metal detection in smart packaging applications.
Mitcharean et al. (Tue,) studied this question.
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