Bacterial Synthesis of Anisotropic Metal Nanoparticles
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چکیده
This chapter describes the biological synthesis of anisotropic metal nanoparticles using the bacterium Actinobacter spp. The biogenic gold nanoparticles thus synthesized show triangular and hexagonal morphology with edge lengths between 0.05 μm to 2 μm. The surface topography of triangular gold particles indicated that they are ~ 9 nm thick. These flat particles show a strong absorption in the near infra-red (NIR) region of the electromagnetic spectrum. Individual nanotriangles were found to be single crystals highly oriented in the (111) crystallographic direction. Biochemical analysis of the process revealed that the reduction of gold ions is mediated by the bacterial cytochrome oxidase. Capping proteins associated with the surface of the triangular particles act as a shape directing agent along the bacterial cell wall. Actinobacter spp. exerts high specificity towards gold ions while fabricating triangular and hexagonal gold particles. Silver nanoparticles synthesized using Actinobacter spp. also result in flat, plate–like structures. Biological reduction of silver ions is possibly mediated by silver binding proteins that bind and stabilize silver nanoparticles.
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