Barium–cobalt nanocomposites have garnered significant attention owing to their tunable optical and electronic properties, which make them promising candidates for advanced functional applications. In this work, the optical band gap of a barium–cobalt nanocomposite was systematically investigated using UV–Visible absorption spectroscopy in conjunction with Tauc plot analysis. The UV–vis absorption spectrum displayed a pronounced absorption edge within the visible region, indicating strong photon absorption capability. The optical band gap energy was evaluated by plotting (αhv)n function of photon energy (hv), where α represents the absorption coefficient and ‘n’ corresponds to the nature of the electronic transition. Extrapolation of the linear region of the Tauc plot to the energy axis yielded an optical band gap value of approximately 5.29 eV for direct transition and 4.47 eV for indirect transition of BaO 1.6 eV/1.19 eV suggesting a direct/indirect allowed transition for Co3O4, and for BaCoO3 direct/indirect transition is 2.9/2.8 respectively which are calculated by using Kubelka-Munk [F(R)] function. The observed modification in band gap energy relative to the bulk counterpart can be attributed to nanoscale effects and interfacial interactions within the composite system. These findings highlight the potential of barium–cobalt nanocomposites for applications in optoelectronic devices, photocatalysis, and energy conversion technologies.

Keywords: Barium–Cobalt Nanocomposite; Optical Band Ga;p Tauc Plot; Photocatalysis;