The uncapped and capped CuO nanoparticles were synthesized by sol–gel process. Oleylamine (OA) was used as a capping agent to control the size and morphology of the CuO nanoparticles. The obtained samples were characterized by means of UV–Visible spectroscopy (UV–Vis), Photoluminescence (PL) spectroscopy, X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR) and Field Emission Scanning Electron Microscopy (FE-SEM) along with energy dispersive X-ray spectroscopy (EDS). UV–Visible technique was used to measure the band gap of the synthesized samples. The optical properties for uncapped and capped CuO nanoparticles were analyzed by the Photoluminescence (PL) spectrum. The XRD spectra of the synthesized samples confirmed the CuO nanoparticles with monoclinic structure. The occurrences of capping agent have been analyzed by Fourier transform-infrared spectroscopy (FT-IR). The FT-IR study revealed that the transmittance peaks at 502 cm-1,603 cm-1 and 674 cm-1 were Cu-O stretching mode, and 677 cm-1 was Cu-O monoclinic phase of the uncapped CuO nanoparticles. In addition 499 cm-1, 576 cm-1 have been Cu-O stretching mode and 686 cm-1 are Cu-O monoclinic phase of the oleylamine capped CuO nanoparticles. Further, FESEM study revealed the morphology of the synthesized samples. Changes occurred on the surface morphology with the addition of a capping agent. Antioxidant of CuO nanoparticles evaluated using L-ascorbic acid and BHA as standards. The antioxidant capacity was expressed as ascorbic acid equivalent. Cyclic voltammetry applications investigated of uncapped and oleylamine capped CuO nanoparticles.