الفهرس 
Title : Effect of nano silica on some biological and histological aspects of cotton leaf worm larvae spodoptera littoralis
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Abstract
The study aims to prepare silica nanoparticles and their effect against larvae of cotton leafworm Spodoptera littoralis. The silica nanoparticles were prepared by sol{u2013}gel method in two forms, Silica nanoparticles hydrophilic (TSiNP HPHI), silica nanoparticles hydrophobic (TSiNP HPHO) from Tetraethyl orthosilicate (TEOS) and nano silica hydrophilic from sodium silicate (SSiNP HPHI) in addition traditional silica (TSi) from sand by grinding the sand in Ball mill device. The obtained silica powders were characterized by using spectroscopy with high resolution Transmission Electron Microscope (TEM). The crystalline shape of the particles was determined using X-ray diffraction (XRD). Chemical bonds were identified By Fourier Transform-Infrared Spectroscopy (FTIR). The results showed that, all particles were in nano size and amorphs form. Nano silica consist of silica and oxygen only in TSiNP HPHI and SSiNP HPHI while TSiNP HPHO nano silica was consist of silica, oxygen and carbon. The effect of silica nanoparticles and traditional silica on the second and fourth larvae of S.littoralis were studied to determine the mortality ratio and estimate LC₅₀ values using four concentrations, 10, 20, 40, 60 g / L. Results showed that all tested concentrations of compounds caused mortality of second and fourth larvae of S. littoralis. The concentrations of 60 and 40g/L for all three nano silica caused100% mortality of second larvae