In vitro Antibacterial Activity and Dye Effluent Treatment Potential of Silver Nanoparticles Synthesized with Paspalum vaginatum Extract

Abstract

Paspalum vaginatum vastly grows in the Southeastern region of Nigeria, but without major known applications. After GC-MS analysis, aqueous extract of its aerial parts of P. vaginatum was employed in silver nanoparticles (AgNPs) biosynthesis. Chromatogram revealed 10 bioactive components in the extract. The synthesized AgNPs exhibited a characteristic UV-Vis absorbance peak at 320 nm, confirming their surface plasmon resonance. Fourier-transform infrared (FTIR) analysis revealed the presence of functional groups such as O–H and N–H stretching, O=C=O stretching and C≡C stretching, suggesting the involvement of biomolecules in nanoparticle stabilization and reduction. Furthermore, X-ray diffraction (XRD) analysis showed prominent peaks at 2θ values of 28.98º, 34.22º, 37.98º, 44.28º and 64.46º, corresponding to the face-centered cubic (FCC) crystalline structure of AgNPs, while dynamic light scattering (DLS) and transmission electron microscopy (TEM) analyses indicated particle sizes of 11.51 ± 2.53 nm (PDI: 0.60) and 3.41 ± 1.60 nm, respectively, highlighting the presence of well-dispersed, nanoscale particles with moderate polydispersity. There were 19.00 ± 2.16 mm and 15.00 ± 2.85 mm zones of inhibition of Escherichia coli and Salmonella sp. growth at 53.3 µg/mL concentration of AgNPs. At 1.72 mg/mL of AgNPs, the percentages of methylene blue and safranin effluent treatment were 37.14 ± 1.63% and 33.76 ± 2.37% after 1 h, 40.38 ± 0.13% and 46.47 ± 1.04% after 2 h and 48.45 ± 0.88% and 53.48 ± 1.13% after 3 h of solar irradiation. These findings demonstrate that the AgNPs synthesized using P. vaginatum extract possess favourable physico-chemical characteristics, which contribute to their appreciable biological and photocatalytic activities.