Chemically engineered CoO_x-doped flower-like NiO nanoparticles for photodegradation of Bisphenol A and Orange II Dye, and genetic screening of toxicity via Caenorhaditis elegans

In this study, pure flower-like NiO nanoparticles (NiO NPs), and CoO_x-doped NiO nanocomposites (NCs) with varying concentrations (2.5 wt%, 5 wt%, 7.5 wt%, and 10 wt%) were synthesized using a simple hydrothermal technique. Characterization through XRD, XPS, FESEM, TEM-EDS, and BET analyses confirmed their unique structural features and composition. CoO_x(2.5 wt%)/NiO NCs exhibited flower-like flakes wedged to the surface of the NiO microspheres, with a measured total pore volume of 0.734 cm³/g and an N₂-BET surface area of 285.18 m²/g. Under UV light, these CoO_x(2.5 wt%)/NiO NCs demonstrated significant photocatalytic efficiency, archiving 98.7 % and 99 % degradation of BPA and O-II dyes within 120 min. This performance is attributed to the formation of a p-n junction at the interface of CoO_x-doped NiO NCs and their flower-like morphology, facilitating effective charge separation and photodegradation. Additionally, toxicity assessment using the C. elegans genetic model focused on stress-responsive genes GST-4, DAF-16, and intracellular ROS. The result showed that the BPA photocatalytic byproduct initially generated intracellular reactive oxygen species (ROS), which gradually diminished over time (60–120 min). In contrast, no evident toxicity was observed for O-II dye byproducts even during short-time degradation. This study not only highlights the efficiency of CoO_x-doped NiO NCs in degrading BPA and O-II pollutants but also provides insights into toxicity dynamics, demonstrating their potential for eco-friendly water purification and enhanced water treatment efficiency.