<p>The sol-gel dip coating approach synthesized cobalt-doped Bi₂O₄ nanostructures with Co doping 1-5wt.%. These nanostructures were ecologically beneficial. X-ray diffraction confirmed the synthesis of a monoclinic phase of Bi₂O₄ thin films. Bismuth oxide thin films with a 5 wt% Co has a higher lattice constant and larger crystallite size. The band gap of thin films decreased with an increase in Co contents, absorbing a large range of the visible spectrum of sunlight. The dielectric constant was increasing and the tangent loss was decreasing with an increase in Co contents, making nanostructures suitable for energy storage applications. The most significant discovery, which showed that cobalt-doped Bi₂O₄ thin films were feasible as low-cost spintronics devices, was the 11.5 emu/cm³ saturation magnetization value for 5wt.% Co doping. Cobalt-doped Bi₂O₄ exhibited elevated antibacterial activity against gram-positive (<i>S. aureus</i>) and gram-negative (<i>E.coli</i>,<i> Klebsiella pneumonia and P. aeruginosa</i>) pathogenic bacteria. Co-doped Bi₂O₄ nanostructures were an alternative to traditional photocatalysts due to their exceptional degradation performance in visible light. Both antibacterial and photo-catalytic activity have synergistic effects against pathogenic bacteria. These nanostructures offered enhanced photocatalytic performance, potential for environmental remediation, medical disinfection, and sustainable development.</p>