Optimized green synthesis of dual-phase metal oxide nanoparticles for environmental remediation

Abstract

This study presents the first reported investigation of Nigella sativa (NS) leaf extract as a natural reducing and stabilizing agent for the green synthesis of copper oxide nanoparticles (NS:CuO NPs). Structural analysis confirmed a mixed monoclinic and cubic phase having crystallite size of 23 nm. The optical study depicted an absorption peak at 361 nm and band gap energy of 2.30 eV. Surface chemistry revealed the functional groups, including O–H, N–H, C–H, C=O, and N–O on the surface of particles, indicating phytochemical capping on the nanoparticle surface. Morphological studies revealed spherical and elongated particles, with diameters of 8–10 nm and lengths ranging from 50 to 125 nm. The NS:CuO NPs showed excellent photocatalytic performance, achieving ∼98 % and ∼89 % degradation of Malachite Green and Congo Red under visible light within 60 min and 140 min, following pseudo-first-order kinetics with a rate constant of 0.05463 , supported min⁻¹ and 0.01548 min⁻¹, respectively. The high efficiency was primarily attributed to superoxide radicalsby other reactive oxygen species. The catalyst maintained over 90 % degradation efficiency after five consecutive cycles.