Eco-friendly synthesis and characterization of ZnO and Mg-Ag-doped ZnO nanoparticles using Phoenix dactylifera L. seeds: exploring biological activity and structural properties

Abstract

This study focuses on the green synthesis of zinc oxide (ZnO) and magnesium-silver-doped zinc oxide (Mg-Ag-doped ZnO) nanoparticles (NPs) via biomass conversion of Algerian Ghars date palm (Phoenix dactylifera L.) seeds. Aqueous extracts of the seeds were utilized as reducing and stabilizing agents in the biogenic synthesis process. Structural, compositional, and morphological analyses, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy-energy-dispersive X-ray analysis (SEM-EDAX), and ultraviolet–visible spectroscopy (UV–Vis), confirmed the successful formation of pure and Mg-Ag-doped ZnO NPs. The UV–Vis absorption spectra showed a shift from 395.6 nm (pure ZnO) to 373.2 nm (Mg-Ag doped), with corresponding energy values increasing from 3.13 to 3.32 eV, indicating changes in electronic structure due to doping. XRD analysis revealed an increase in average crystallite size from 12.8 nm (ZnO) to 22.0 nm (Mg-Ag ZnO) and a noticeable shift in peak positions, confirming successful doping. Biological evaluations demonstrated that Mg-Ag-doped ZnO NPs exhibited enhanced photocatalytic, antibacterial, antioxidant, and antidiabetic activities compared to undoped ZnO NPs. Notably, Mg-Ag ZnO NPs showed superior antioxidant activity with an IC₅₀ of 10.78 mg mL⁻¹ and EC₅₀ of 0.79 mg mL⁻¹, compared to ZnO NPs with an IC₅₀ of 11.51 mg mL⁻¹ and EC₅₀ of 0.84 mg mL⁻¹. They also exhibited higher photocatalytic degradation efficiency of methylene blue dye (93% vs. 87% for ZnO) under UV light. Antibacterial studies showed that Mg-Ag ZnO NPs had lower minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) than pure ZnO NPs, with a MIC of 0.625 mg mL⁻¹ and MBC of 0.625 mg mL⁻¹ for E. coli, compared to 2.5 and 10 mg mL⁻¹, respectively, for pure ZnO. Furthermore, Mg-Ag-doped ZnO NPs exhibited significant α-amylase inhibition (48.0% at 0.25 mg mL⁻¹), outperforming pure ZnO NPs (38.9% at the same concentration), and showed competitive inhibition to the reference drug acarbose in antidiabetic tests. These findings highlight the potential of rationally designed biogenic ZnO nanostructures synthesized through biomass conversion of P. dactylifera seeds, especially after strategic doping, for various biomedical and environmental applications. This green synthesis approach, utilizing renewable biomass, offers an eco-friendly and sustainable route for producing ZnO-based nanomaterials with tunable properties.