Green Synthesis of Silver Nanoparticles using Aqueous Extract of Aerial Parts of Paspalum vaginatum: Characterization, Antibacterial and Mosquito Larvicidal Analyses

The sustenance of the benefits of biological methods of nanoparticle synthesis requires an urgent shift in the sources of suitable extracts to include the lesser economically and medicinally essential plants. This study aimed to determine the suitability of extracts of aerial parts of Paspalum vaginatum for the green synthesis of biologically active silver nanoparticles (AgNPs). P. vaginatum aqueous extract was subjected to various standard phytochemical tests and thereafter utilized in the synthesis of silver nanoparticles (Pv-AgNPs). Then the physicochemical, antibacterial and mosquito larvicidal properties of the synthesized Pv-AgNPs were evaluated. The results revealed the presence of phenolic compounds, proteins, flavonoids, amino acids, alkaloids, and carbohydrates in the extract. Fourier Transform Infrared (FTIR) spectroscopy showed the functional groups, including O-H stretching, C≡C stretching, N-H stretching, O=C=O stretching, and C-H bending in the Pv-AgNPs. The nanoparticles had 31.51±2.53 nm average size in solution, with 0.598 polydispersity index, determined using the Dynamic Light Scattering (DLS) analysis. The Transmission Electron micrograph indicated an average nanoparticle size of 3.41±1.60 nm. At 53.3, 26.7 and 13.3 µg/mL concentrations, the resulting Pv-AgNPs exhibited 21.01±2.2 mm, 16.67±2.1 mm and 13.20±2.2 mm zones of clearance against growth of E. coli, but 19.67±4.6 mm, 12.70±4.9 mm and 10.70±4.2 mm against Staphylococcus sp. growth, respectively. The time-dependent larvicidal activity of 0.44 mg/mL Pv-AgNPs concentration showed 0.00±0.00%, 50.00±4.08% and 90.00±4.08% mortality at 1 h, 6 h, and 26 h of exposure. Consequently, extract of aerial parts of P. vaginatum is potentially suitable for biosynthesis of nanoparticles that possess appreciable biological activities.