YOHANNES SHUKA JARA2026-02-042024-06https://etd.hu.edu.et/handle/123456789/615Herein, nitrogen-zinc-codoped copper nanoparticles (N-Zn-CuO NPs) was successfully synthesized by using Pycnostachys Abyssinica Fresen plant leaf extract as a bioreducing and capping agent for the photocatalytic degradation of methylene blue under natural sunlight irradiation. Additionally, pure CuO NPs, N-CuO NPs, and Zn-CuO NPs were also biosynthesized for comparison. Characterization techniques of UV-Vis, XRD, SEM, FT-IR revealed that N-Zn-codoping narrowed the band gap (1.72 to1.07 eV), reduced the crystallite size (25 to11.23 nm), distortion of monoclinic crystal lattice (rhombus and diamond like shape with an average diameter of 2.25 µm to irregular shape with an average size of 2.75 µm), and towards redshift of the Cu-O characteristic peaks (617 to 529 cm-1 ) of CuO NPs, respectively, confirmed the successful incorporation of dopants into CuO NPs. The effects of key parameters on the photocatalytic degradation efficiency of all biosynthesised NPs were investigated. The optimal conditions with maximum degradation for N-Zn-CuO NPs were determined to be 3% dopant concentration for both N and Zn, 120 mg of photocatalyst dosage, pH of solution at 11, 20 ppm of Initial dye concentration and 30 minutes of reaction time. Photocatalytic activity towards methylene blue (MB) dye degradation under 30 minutes exposure to sunlight was 99.75% for N-ZnCuO NPs, outperforming pure CuO NPs (95.76%), N-CuO NPs (97.93%), and Zn-CuO NPs (98.26%) under optimal conditions. The enhanced photocatalytic performance of NZn-CuO NPs is attributed to their tailored optical properties, leading to improved charge separation and reduced recombination. Kinetic studies revealed a strong fit (R2=0.99799) with the BMG kinetic model for N-Zn-CuO NPs, indicating surface-mediated degradation of MB. Furthermore, the nanocatalysts exhibited excellent reusability and stability over four cycles. This finding highlights the potential of biosynthesized N-Zn-CuO NPs as highly efficient, simple, eco-friendly and sustainable solutions for the degradation organic pollutants.BiosynthesisDoping and codopingMethylene blueN-Zn-codoped CuO NPsPhotocatalytic degradationPycnostachys AbyssinicaThesis