Biogenic synthesis and characterization of lanthanum oxide nanoparticles using citrus sinensis peel waste for antifungal applications in crop protection.

INTRODUCTION

Green synthesis of metal oxide nanoparticles using agricultural waste offers a sustainable approach to developing alternative antifungal agents. This study investigated the potential of lanthanum oxide (La2O3) nanoparticles synthesized using Citrus sinensis peel extract as an eco-friendly antifungal agent against important phytopathogens.

METHODS

La2O3 nanoparticles were synthesized using C. sinensis peel extract and characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), UV-visible spectroscopy (UV-Vis), field-emission scanning electron microscopy (FESEM), and energy-dispersive X-ray spectroscopy (EDX). Their antifungal activity was evaluated against Alternaria solani and Colletotrichum capsici at different concentrations and compared with the commercial fungicide SAAF.

RESULTS

The synthesized La2O3 nanoparticles exhibited a crystalline cubic structure with characteristic physicochemical properties. FESEM analysis revealed irregular, flake-like to quasi-spherical particles, while EDX confirmed the presence of lanthanum, oxygen, and carbon. The nanoparticles demonstrated concentration-dependent antifungal activity against both pathogens. A. solani was more susceptible, with complete growth inhibition at 5 mg/mL, whereas inhibition of C. capsici reached 86.8% at 15 mg/mL. Complete suppression of sporulation was observed in La2O3-treated cultures. Against A. solani, La2O3 nanoparticles at 15 mg/mL, earlier than the commercial fungicide at 5 mg/mL.

DISCUSSION: The findings demonstrate that C. sinensis peel-derived La2O3 nanoparticles possess substantial antifungal activity, particularly against A. solani. The combined physicochemical characterization and antifungal results support their potential as an eco-friendly biocontrol agent while highlighting the need for further optimization and evaluation against comparatively more resistant pathogens such as C. capsici.