Green synthesis of silver nanoparticles using chitosan extracted from Penaeus indicus and its potential activity as aquatic larvicidal agent of Culex pipens

In the present study, silver nanoparticles (AgNPs) were greenly synthesized using two different reducing/capping agents, chitosan (Cs) and Molar Hinton Broth (MHB) agar. With the use of Fourier transform infrared spectroscopy (FTIR), the potential functional groups responsible for reducing/capping silver ions were determined, as well as the characterization and computation of the degree of deacetylation of the produced chitosan employed in AgNPs synthesis. The synthesized silver nanoparticles were validated and described using ultra-violet (UV–Vis) spectrophotometric analysis for surface plasmon resonance and a transmission electron microscope (TEM). Also, the AgNPs solutions were evaluated to combat the aquatic larvae of Culex pipens. The results revealed that silver ions can be reduced by both chitosan and MHB agar to generate well stable silver nanoparticles solution although chitosan has weaker reduction properties. UV–vis spectrum for both AgNPs solutions showed a single absorption peak of 400 nm range indicating that the nanoparticles exist and are spherical in shape. TEM analysis showed both AgNPs are round in shape with an average size of 5 to 15 for MHB-AgNPs and from 10 to 50 for chitosan silver nanoparticles Cs-AgNPs. The findings of combat of aquatic larvae of mosquito showed the superiority of CS-AgNPs over MBH-AgNPs in killing mosquito larvae with LC₅₀ (279.33, 321.33, and 367.37 µM) and LC₉₀ (468.85, 505.84, and 568.07 µM) while (MBH-AgNPs) showed less effectiveness with LC₉₀ (483.87, 543.12, and 611.4 µM) and LC₉₀ (870.23, 811.97, and 967.91 µM), respectively. In conclusion, the greenly synthesized silver nanoparticles have the potential to be used as an alternative eco-friendly larvicide for mosquito control in its larval aquatic stages.