Enhanced photocatalytic degradation and antimicrobial activities of biogenic Co3O4 nanoparticles mediated by fenugreek: sustainable strategies†

The present study introduces Trigonella foenum-graecum (TFG, fenugreek)-mediated Co₃O₄ nanoparticles (NPs) as an innovative solution for eliminating industrial azo dyes from contaminated water. The novelty lies in their rapid, cost-effective synthesis and excellent photocatalytic and antimicrobial performance, which mark a significant advancement in environmental remediation. The NPs are synthesized using a co-precipitation method and characterized through advanced techniques. UV-visible absorption spectroscopy revealed two prominent direct bandgap transitions, surpassing previous reports and enhancing light absorption for efficient photocatalysis. FTIR analysis confirmed the successful incorporation of TFG phytochemicals, while XRD and SAED patterns indicated high crystallinity, a small crystallite size (1.6 nm), and ultrafine average particle size (5.5 nm) as observed by HRTEM. XPS analysis validated the synthesis with controlled oxidation states and defect sites featuring Co²⁺ and Co³⁺ ions. The optimized synthesis process led to outstanding photocatalytic performance, achieving 100% degradation of Congo red dye in just 60 minutes at a concentration of 120 mg L⁻¹. This efficiency underscores their capability to treat CR-contaminated water under specific conditions. The synergy between TFG phytochemicals and Co₃O₄ NPs demonstrates significant potential for water pollution remediation. Additionally, these NPs exhibit strong antimicrobial activity against Gram-negative and Gram-positive bacteria, highlighting their broader environmental significance and potential applications in various ecological fields.