Phyto-fabrication of Rubidium-Doped Co 3 O 4 Nanostructures: Crystallo-Chemical Investigation and Eosin Yellow Dye Degradation and Antibacterial Activity Applications

Introduction: This study reports a facile, sustainable, and green synthesis of pure Co 3 O 4 and rubidium-doped Co 3 O 4 (Rb-Co 3 O 4 ) nanoparticles using Tridax procumbens leaf extract to enhance photocatalytic and antibacterial performance. Methods: The synthesized nanoparticles were characterized by PXRD with Rietveld refinement for crystal structure, electron density mapping, and crystallo-chemical analysis, along with UV-Vis DRS, FT-IR, EDX, FE-SEM, PL, HR-TEM, and XPS. Photocatalytic activity was evaluated through sunlight-assisted degradation of eosin yellow dye, while antibacterial activity was assessed against selected microorganisms. Results: Rietveld refinement confirmed the cubic crystalline structure of Rb-Co 3 O 4 with a crystallite size of 50.87 nm. FT-IR spectra showed characteristic Co-O vibrations at 651 and 567 cm −1 . EDX analysis confirmed the presence of cobalt (77.7%), oxygen (20.9%), and rubidium (6.5%). Rubidium doping significantly enhanced photocatalytic performance, increasing eosin yellow degradation efficiency from 72% to 92% and the apparent rate constant from 4.96 × 10 −3 to 1.06 × 10 −2 min −1 . Rb-Co 3 O 4 nanoparticles also exhibited superior antibacterial activity compared with pure Co 3 O 4 . Discussion: The improved photocatalytic and antibacterial activities are attributed to the beneficial effects of rubidium doping, which enhanced the structural and surface properties of Co 3 O 4 nanoparticles, promoting efficient charge separation and reactive species generation. Conclusion: Green-synthesized Rb-Co 3 O 4 nanoparticles demonstrate enhanced structural characteristics, photocatalytic efficiency, and antibacterial activity, highlighting their potential for environmental remediation and antimicrobial applications.