Nanoflower-Shaped ZnO Nanoparticles Reduced with Blueberry Waste and Their Evaluation of Malachite Green Dye Degradation

This work focuses on the green synthesis of zinc oxide nanoparticles (ZnO NPs) to be used as a photocatalyst, preparing a blueberry (Vaccinium corymbosum) extract as a reducing agent, zinc chloride as a precursor, and NaOH as precipitating agent (1, 7 and 14 M). Characterization techniques included X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible (UV-Vis), Fourier-transform infrared (FTIR), X-ray photoelectron (XPS), and Raman spectroscopy. The XRD analysis confirmed the hexagonal wurtzite crystalline structure of ZnO NPs, while the SEM and TEM revealed a flower-like morphology. Moreover, the ZnO NPs exhibited a band gap energy in the range of 3.17 to 3.27 eV, depending on the concentration of NaOH. Regarding the photocatalytic activity, the synthesized ZnO NPs showed a photocatalytic efficiency greater than 90%, degrading malachite green (MG) dye in 60 min under sunlight. The proposed photocatalytic mechanism includes reactive oxygen species (ROS) generation (hydroxyl radicals (OH•) and superoxide radicals (O2−)). The XRD and Raman analysis also revealed that the ZnO NPs maintained structural integrity after repeated photocatalytic cycles, emphasizing their stability and suitability for practical applications.