Hassan Korbekandi

Silver nanoparticles (NPs) have been the subjects of researchers because of their unique properties (e.g., size and shape depending optical, antimicrobial, and electrical properties). A variety of preparation techniques have been reported for the synthesis of silver NPs; notable examples include, laser ablation, gamma irradiation, electron irradiation, chemical reduction, photochemical methods, microwave processing, and biological synthetic methods. This review presents an overview of silver nanoparticle preparation by physical, chemical, and biological synthesis. The aim of this review article is, therefore, to reflect on the current state and future prospects, especially the potentials and limitations of the above mentioned techniques for industries.

Recent developments in the biosynthesis of nanomaterials have demonstrated the important role of biological systems and microorganisms in nanoscience and nanotechnology. These organisms show a unique potential in environmentally friendly production and accumulation of nanoparticles with different shapes and sizes. Therefore, researchers in the field of nanoparticle synthesis are focusing their attention to biological systems. In order to obtain different applied chemical compositions, controlled monodispersity, desired morphologies (e.g., amorphous, spherical, needles, crystalline, triangular, and hexagonal), and interested particle size, they have investigated the biological mechanism and enzymatic process of nanoparticle production. In this review, most of these organisms used in nanoparticle synthesis are shown.

Abstract BACKGROUND: The objectives of this study were optimization of silver nanoparticle synthesis using biotransformations by Lactobacillus casei subsp. casei, and studying the location of nanoparticles synthesis in this microorganism. RESULTS: The presence of AgNO 3 (0.1 mmol L −1 ) in the culture as the enzyme inducer, and glucose (56 mmol L −1 ) as the electron donor in the reaction mixture had positive effects on nanoparticle production. By gradually increasing the concentration of AgNO 3 (as the substrate) to 6 mmol L −1 , nanoparticle production was increased. By increasing biomass, nanoparticles production was also increased. Biosynthesized silver nanoparticles were almost spherical, single (25–50 nm) or in aggregates (100 nm), attached to the surface of biomass or were inside and outside of the cells. CONCLUSION: The present study demonstrated the bioreductive synthesis of silver nanoparticles using L. casei subsp. casei at room temperature. In this research, and due to experience in optimization of biotransformation reactions, the reaction conditions were successfully optimized to increase the yield of nanoparticles production and productivity of this biosynthetic approach. Copyright © 2012 Society of Chemical Industry

The objectives of this study were the biosynthesis of silver nanoparticles (NPs) by biotransformations using Saccharomyces cerevisiae and analysis of the sizes and shapes of the NPs produced. Dried and freshly cultured S. cerevisiae were used as the biocatalyst. Dried yeast synthesized few NPs, but freshly cultured yeast produced a large amount of them. Silver NPs were spherical, 2-20 nm in diameter, and the NPs with the size of 5.4 nm were the most frequent ones. NPs were seen inside the cells, within the cell membrane, attached to the cell membrane during the exocytosis, and outside of the cells.