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The biological production of metal nanoparticles is becoming a very important field in chemistry, biology, and materials science. Metal nanoparticles have been produced chemically and physically for a long time; however, their biological production has only been investigated very recently. The biological reduction of metals by plant extracts has been known since the early 1900s; however, the reduction products were not studied. Furthermore, the synthesis of nanoparticles using plant materials, for the most part, has only recently been studied within the last three decades, while the production of nanoparticles using living plants has only been studied in the last half decade. The synthesis of metal nanoparticles using biological materials has been shown to produce nanoparticles of the same shapes and sizes as those produced through chemical or physical methods. For example alfalfa, wheat, and oat biomasses are able to reduce Au(III) to Au(0) forming face centered cubic (FCC), tetrahedral, decahedral, hexagonal, icosahedral multitwinned, irregular shape, and rod shape gold nanoparticles. Most of these nanoparticles had sizes ranging from 10 to 50 nm in diameter. Also it has been demonstrated that living alfalfa plants are capable of reducing Au(III) and Ag(I), producing gold and silver nanoparticles. The use of high resolution-TEM showed that the plants formed small silver nanoparticles with sizes averaging from 2 to 20 nm in diameter. These results have proven that biological materials provide an environmentally friendly or green chemistry method to produce invaluable materials because the biosynthesis eliminates the need to use harsh or toxic chemicals. The synthesis of metal nanoparticles using plant-derived materials is a simple yet effective method for the production of nanoparticles. Finally, the applications of nanoparticles are making the fields of nanoscience and nanotechnologies grow rapidly. Researchers have found uses for nanoparticles in medicine, catalysis, bio-sensors, chemical sensors, environmental remediation, semi-conductors, and photovoltaic devices, among others. |
