author(s)
Abdul Aziz BM Barnawi, Tariq S Alghamdi, Jazem A Mahyoub and Khalid M Al-Ghamdi

abstract
This study aims to use Brown Algae extract, Sargassum natans as a biological agent for reducing silver nitrate to silver nanoparticles and evaluate their effectiveness in controlling of Aedes aegypti that transfer dengue fever in Jeddah province. The fourth-year larvae were exposed to different concentrations of both the extract alone and the silver nanoparticles prepared from it according to the WHO standard method. The silver nanoparticles were characterized using UV-visible spectroscopy, scanning electron microscope and IR spectroscopy. The larvae sensitivity to the extract was ecaluated before and after the addition of the nitrate. The results showed that the silver nanoparticles were nearly 1.46 times superior against larvae compared to the extract alone. The values ​​of the lethal concentrations for 50% (LC₅₀) of the treated larvae were 282.55 ppm for the extract and 194.5 ppm for silver nanoparticles. The results of this study revealed the presence of deformations in the larvae treated with both the extract and nanoparticles and these effects were observed all stages of growth, which caused in the destruction of the insect without completing its life cycle.