Photoluminescence, Raman scattering and photocatalytic properties of Pd doped ZnO nanostructures synthesized via wet chemical route

Pristine ZnO and palladium (Pd)-doped ZnO nanostructures were synthesized via wet chemical route and characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), Ultraviolet (UV)- visible (Vis) spectroscopy, Photoluminescence (PL) and Raman spectroscopy. XRD analysis confirmed the hexagonal wurtzite structure of ZnO with a secondary phase of metallic Pd revealing the partial Pd doing into ZnO lattice because of difference in ionic radii of Zn²⁺ (0.074 nm) and Pd ²⁺ (0.080 nm). Moreover, morphological transformation from irregular shaped nanostructures to spherical shaped nanostructures with random agglomeration was observed in SEM micrographs. The enhanced visible light absorption due to surface plasmon resonance effect and a slight decrease in energy band gap values were observed in Pd/ZnO nanostructures. Moreover, PL investigations revealed that the incorporation of Pd into ZnO leads to a decrease in defects related emissions. Finally, the photocatalytic efficiency of prepared samples was evaluated against Methylene blue dye, which was 23.3% for pristine ZnO, and it was observed to increase up to 48.5% in 150 min in the case of 3% Pd-doped ZnO under sunlight irradiation. In addition, the plausible mechanism was proposed for enhanced photocatalytic efficiency resulting from Pd-doped ZnO nanostructures.