^aDepartment of Chemistry, KPR Institute of Engineering and Technology,

Coimbatore-641407, India

^bDepartment of Chemistry, PSG College of Arts & Science, Coimbatore -641014, Tamilnadu, India

^cDepartment of Mechanical Engineering, Kongu Engineering College, Perundurai 638052, Tamilnadu, India

^dDepartment of Humanities and Sciences, Gokaraju Rangaraju Institute of

Engineering and Technology, Hyderabad, 500090, Telangana, India

Zinc oxide nanoparticles were chemically synthesised and characterised by UV-DRS spectroscopy, FTIR, scanning electron microscopy with energy-dispersive X-ray diffraction, and X-ray powder diffraction. In order to evaluate the impact of the synthesis process on the structural parameters, Rietveld refinement was done using the GSAS-II programme on experimentally acquired XRD data. ZnO was found to have a hexagonal structure with lattice parameters of a = b =3.247 Å; c = 5.205Å and an average size of about 20-40 nm, as determined by Rietveld refinement of XRD and SEM data. FTIR and EDX analysis was used to confirm the functional group and elemental composition of ZnO NPs. The UV-DRS spectra revealed that the synthesised ZnO had an optical band gap of

3.05 eV. Parametric investigations ofthe surface morphology of ZnO nanostructures were conducted using the Gwyddion programme. Pseudo-first-order rate kinetics were observed for the photodegradation of two cationic dyes, MB (87.87%) and RhB (74.79%), in the presence of UV light.