Photocatalytic removal of anionic and cationic dyes: A comparative study using ZnO nanoparticles obtained with Capsicum annuum L. var. mirasol extract

Green synthesis strategies have emerged as sustainable alternatives to generate functional nanomaterials. In this research, ZnO nanoparticles were obtained using Capsicum annuum L. var. mirasol extract as an eco-friendly biogenic mediator acting as a stabilizer. TEM imaging showed a particle size of 15.49 nm, while XRD analysis showed a crystallite size of 11.95 nm. The proximity of these values confirms the material's nanocrystalline structure. FTIR spectroscopy showed a characteristic Zn–O stretching vibration band in the 400–600 cm⁻¹ region, confirming ZnO formation. Photocatalytic activity was assessed through the UV-induced degradation of 15 organic dyes. The synthesized ZnO nanoparticles demonstrated high photocatalytic efficiency under UV irradiation. Almost complete degradation was achieved for methylene blue, rhodamine B, yellow eosin, Congo red, amido black 10B, bromophenol blue, eriochrome black T, and indigo carmine. High efficiencies were also observed for basic fuchsin (99.51 ± 0.48), crystal violet (99.32 ± 0.68), and malachite green (96.11 ± 1.15), confirming enhanced photocatalytic activity toward both cationic and anionic dyes. Scavenger assays were done to elucidate the role of ROS in the photocatalytic mechanism. Both Gram-positive and Gram-negative strains were utilized to determine the antibacterial profile of the synthesized ZnO. The nanostructures displayed formidable antimicrobial activity, particularly toward B. subtilis and S. aureus , which showed the highest sensitivity during the assay. Furthermore, biofilm assays demonstrated a 73.64% reduction in the development of S. aureus biofilm. Collectively, the findings indicate that ZnO nanoparticles synthesized using mirasol pepper extract are multifunctional materials with potential applications in environmental remediation and antimicrobial treatments.