Exploration of grown cobalt-doped zinc oxide nanoparticles and photodegradation of industrial dye

•Co2+ doped ZnO and bare ZnO nanoparticles with wurtzite structure were developed.•PL spectrum of ZnO NPs changes from dual bands to single band with dopants.•The bandgap and defect states of ZnO NPs reduce with dopants.•The average PL lifetime of Co-ZnO NPs decreases from 14.05 ns (pure ZnO NPs) to 4.66 ns.•20% Co2+ doped ZnO NPs shows superior photocatalytic activity for dye degradation. Cobalt-doped and undoped zinc oxide (ZnO) nanoparticles (NPs) with different dopant concentrations were synthesized via the sol-gel method. The structural, morphological, and optical properties of the synthesized NPs were investigated using various techniques. The NPs exhibit a wurtzite structure with an average crystallite size of 20–34 nm. Change in photoluminescence (PL) spectra from dual to single band with dopants suggested decreasing surface state contribution. The PL lifetime of the 430 nm band is too short (