In this research, a novel synthesis of CaONPs has been developed via an environmentally friendly, green method. Garlic extract (Allium sativum) was used as a green-reducing and stabilizing agent for CaONPs. The average particle size of CaONPs was approximately 24.42 nm. The synthesized CaONPs were identified by using Fourier transform infrared (FT-IR) spectroscopy, U.V.-vis spectrum, X-ray diffraction (XRD), Field Emission-Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy, transmission electron microscopy (TEM), Energy Dispersive X-ray spectroscopy (EDX), Atomic Force Microscopy (AFM), and zeta potential (Zp) analysis. The current study highlights the notable applications for CaONPs. First, an antimicrobial assay revealed a high antibacterial and antifungal activity, with the maximum zone of inhibition observed at different concentrations of CaONPs. Secondly, adsorbent for CaONPs in an aqueous solution containing M+2 ions (Co, Ni, Cu). The removal percentages (R%) were Co (II) 93.47%, Ni (II) 87.58%, and Cu (II) 88.53%. Thirdly, the study of fenugreek under water stress revealed that CaO-NPs positively enhance water stress tolerance.
