Rubidium-doped zirconia nanoparticles: Green synthesis, structural characterization, and enhanced photocatalytic degradation of malachite green dye

Dye pollution from industrial effluents poses a significant environmental risk due to its toxicity, persistence, and resistance to conventional treatment methods. In this research article, the pure zirconia (ZrO 2 ) and rubidium doped zirconia (Rb-ZrO 2 ) nanoparticles (NPs) were synthesized as an effective solution, showing enhanced catalytic efficiency for the degradation of dye pollutant under optimized conditions. The eco-friendly synthesis of ZrO 2 and Rb-ZrO 2 NPs was achieved using Anisomeles malabarica (A. malabarica) leaf extract. Various analytical methods, such as UV-Vis DRS, FT-IR, PXRD, EDX, FE-SEM, XPS, PL and HR-TEM were used to thoroughly characterize the structural, optical, electronic properties of NPs. The stretching vibration of Zr-O was verified by FT-IR spectral peaks at 748 and 651 cm⁻¹. The formation of monoclinic and tetragonal crystalline structures of ZrO 2 NPs was validated by PXRD results. In the XPS spectrum, maximum binding energies of rubidium were found at 109.59 eV (3d 3/2 ) in the 3d of Rb-ZrO 2 NPs. The elemental composition of zirconium (61.2%), Rubidium (6.8%) and oxygen (38.8%) was confirmed by EDX analysis of Rb-ZrO 2 NPs. Rb-ZrO 2 NPs showed improved degradation efficiency (85.5%) against malachite green compared to pure ZrO 2 NPs (72%) under UV irradiation within 60 min at pH 7, with a rate constant of 3.08 × 10 −2 min −1 , confirming their enhanced photocatalytic capability. Similarly, Rb-ZrO 2 NPs showed remarkable antibacterial activity toward Listeria monocytogenes among the examined strains.