Bio-combustion synthesis of silver nanoparticles and evaluation of their effective antibacterial and photodegradation properties

The green chemistry approach in synthesizing nanoparticles, particularly using plant extract, has gained booming demand for eco-friendly nanotechnology, evaluating their multifunctional properties, and exploring potential applications. Hence, addressing the need for sustainable nanomaterials in biomedical and environmental fields. This work describes the synthesis of silver nanoparticles (AgNPs) using Manilkara zapota (M. zapota) leaf extract as a reducing agent through a simple bio-combustion method. The synthesized AgNPs were characterized by various analytical techniques such as UV-visible spectroscopy, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and so on. The optical studies of the AgNPs reveal a bandgap energy of about 3.31 eV. The nanoparticles synthesized in this work were found to crystallize in a cubic phase, corresponding to JCPDS #96-9013046, in the Fm-3 m space group. The crystallite size was 22.38 nm and was independently confirmed through the W-H plot (24.75 nm). Infrared spectroscopy results revealed the characteristics of O-H stretching at 3335 cm⁻¹ and a metal peroxide peak at 849 cm⁻¹, respectively. It was seen that the SEM and TEM images depict a clustered agglomeration of the nanoparticles, while EDAX confirmed the elemental composition. The as-synthesized AgNPs showed high catalytic efficiency towards degradation of MB dye (83.33%) following 0th order kinetics with an R² value of 0.98 and rate constant k₀ of 0.007, under acidic conditions at pH-2 being optimal for their performance. The antibacterial assays showed that AgNPs were effective against both Staphylococcus aureus (gram-positive) and Escherichia coli (gram-negative) bacterial strains. Activity was observed at a low concentration of 400 µg/mL. Hence, the obtained AgNPs prepared via bio-combustion route resulted in a potential multifunctional nanomaterial with strong catalytic properties coupled with antibacterial activity.