Paper Title
Green Synthesis of Silver Nanoparticles using Seaweeds Extracts; Characterization and Efficacy Against the Toxic Cyanobacterium Microcystis Aeruginosa

Abstract
Sargassum cinereum and Turbinaria decurrens aqueous extracts were used as a reducing agent for the synthesis of silver nanoparticles (Ag-NPs). The prepared Ag-NPs have plasmon absorption band at ≈ 400 nm. From the FT-IR results, the reduction has mostly been carried out by hydroxyl, carboxyl and amide groups present in S. cinereum and T. decurrens decurrens. TEM images shown that most particles are spherical in shape with no aggregations or debris were detected. The concentration of Ag-NPs was 460 × 10³ and 410 ×10³ NPs / ml and average size of 45 and 25 nm for S. cinereum and T. decurrens, respectively. A high repulsive and attractive forces between each nanoparticle were confirmed with average zeta potential -30.8 and -34.1 mV for S. cinereum and T. decurrens, respectively. On the other hand, the activity of Ag-NPs on the toxic cyanobacterium Microcystis aeruginosa was detected by determine the growth and photosynthetic pigment content under different concentration of Ag-NPs (2, 4, 6, 8 and 10 %) for 7 days of incubation. Generally, both NPs showed reproducible effective antialgal activity with no significant differences between activity of the two NPs against growth and photosynthetic pigments of the toxic cyanobacterium. Keywords - Ag-NPs, Microcystis aeruginosa, Sargassum cinereum, Turbinaria decurrens