ZnO-Functionalized Carbon Dots/Poly(methyl methacrylate)-Grafted Natural Rubber Nanocomposites as an Efficient Absorbent for Industrial Dye Removal

This study presents the fabrication of a multifunctional nanocomposite by incorporating zinc-functionalized carbon dots (Zn-f-CDs) into poly(methyl methacrylate)-grafted natural rubber (PMMA-g-NR) via solution mixing and solvent casting. Zn-f-CDs were synthesized hydrothermally using varying ZnO concentrations, with Zn-f-CDs-5 selected based on their optimal fluorescence, colloidal stability, and surface functionality. Morphological and elemental analyses using FESEM and EDAX validated the structural integrity and composition of the functionalized carbon dots. Incorporating 4 phr Zn-f-CDs-5 into PMMA-g-NR significantly enhanced mechanical performance, increasing tensile stress by 87% and improving storage modulus due to strong interfacial interactions between Zn-f-CDs and the polymer chains. The glass transition temperature (Tg) also shifted from −58 to −54 °C, indicating restricted polymer chain mobility. Thermal analysis revealed improved stability with an increase in initial and maximum degradation temperatures and higher char yield at 700 °C. High-resolution transmission electron microscopy confirmed uniform dispersion of Zn-f-CDs-5 within the PMMA-g-NR matrix. Beyond mechanical, dynamic mechanical, and thermal improvements, the nanocomposite demonstrated excellent dye absorption properties, achieving up to 82% removal of Rhodamine B (RhB) under dark conditions within 72 h. This performance is attributed to the high surface area and functional group density of Zn-f-CDs within the PMMA-g-NR matrix. Overall, the PMMA-g-NR+Zn-f-CDs nanocomposite exhibits a synergistic enhancement in structural and environmental performance, making it a promising candidate for advanced applications in wastewater treatment and sustainable functional materials.