The Synthesis of Metallic Nanoparticles Inside Live Plants
There is increasing commercial demand for metallic nanoparticles due to their applicability in a growing number of fields, e.g. electronics, catalysis, chemistry, energy, and medicine. Nanoparticles are most often produced by wet chemical methods, where the chemicals used are often toxic and flammable. In this work, we describe the results of experiments where metallic nanoparticles are synthesized within the cells of live plants. We have adopted the generic term, phytosynthesis to describe this process. Nanoparticles of common heavy metal ions, e.g. Cu, Co, Zn, Ni, and the noble metals Ag, Au were synthesized by exposing the known metal accumulators Brassica juncea and Medicago sativa to aqueous metal salt solutions. The influence of exposure time, substrate metal ion concentration and chelating agent addition on the uptake of metals were all investigated.Brassica juncea was found to be the best plant for sequestering metals from aqueous solutions and depositing them as intracellular nanoparticle. Furthermore, we were able to show, for the first time, that the size and shape of the nanoparticles, measured by transmission electron microscopy, could be coarsely controlled by varying the growth conditions. This suggests that using plants as biological factories to synthesize tailored nanoparticle materials might be achievable in the foreseeable future.