الفهرس 
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Abstract
This work is based on two principal points, the first was to biosynthesize silver/silver chloride nanoparticles by using the aqueous extract of two different microalgal strains, the green unicellular microalga; Parachlorella kessleri SAG211-11 and the filamentous cyanobacterium strain; Nostoc sp. PCC7524. The biosynthesized nanoparticles were then identified and their physicochemical properties were assigned. The second point was to evaluate the nematicidal activities of biosynthesized nanoparticles (Ag/AgCl-NPs) against juveniles of M. incognita at 2nd larval instars as well as the eggs hatching ability. The most important results can be summarized as the following points:
1- The biosynthesis of Ag/AgCl-NPs was visually confirmed by obvious change in color of the reaction mixture of the algal extract into brown.
2-The UV-Vis spectroscopy analysis confirmed the biosynthesis of small, stable and polydispersed Ag/AgCl-NPs with surface Plasmon absorbance at 414 nm and 424 nm for the nanoparticles formed by P. kessleri and Nostoc sp. respectively.
3- Transmission electron microscopy (TEM) micrographs revealed that the biosynthesized Ag/AgCl-NPs were spherical and in the nanoscale.
4- Also, the XRD pattern assessed the presence of pure cubic crystals of Ag/AgCl-NPs.
5- Fourier transform infrared spectroscopy (FTIR) spectrum revealed that, proteins or proteins combined with polysaccharides, that existed in the aqueous algal extract, were responsible for the reduction of Ag+ ions and hence, biosynthesis and stabilization of Ag/AgCl-NPs by P. kessleri and Nostoc sp., respectively.
6- Surface charge analyses by Zeta sizer instrument revealed that, the Ag/AgCl-NPs of P. kessleri recorded an average potential value of -33.5 mv compared to -18.0 mv of those of Nostoc sp. The high potential value supports well long-term stability, good colloidal nature, and high dispersity of these Ag and AgCl-NPs.
7- The formed Ag/AgCl-NPs exhibited powerful nematicidal potential against the tomato root knot nematode; M. incognita causing inhibition of eggs hatchability and increasing in larval mortality up to 100 % .
8- Therefore, aqueous extracts of P. Kessleri and Nostoc sp. can be used as simple, low cost and ecofriendly environment biomaterial for the large-scale production of Ag/AgCl–NPs which .could be used as powerful nematicide.