Synthesis of Nanomaterials—III (Biological Methods)

Abstract

In his, very famous speech delivered in 1959, before the scientists of American Physical Society, Nobel Laureate Richard Feynman asked the scientists to derive the inspiration from Mother Nature to make the things smaller and see the advantages of making things smaller. Indeed the biological world, animal kingdom and plants make optimum use of materials and space. Nature indeed makes use of small spaces and corresponding confinement to synthesize inorganic materials or minerals abundantly found in earth’s crust. It uses insoluble, complex organic molecules as a reactor in which nucleation and growth of complex and hierarchical structures of inorganic materials takes place by reactions of organic soluble molecules. When we think of biological world, we normally think of delicate, temperature sensitive, carboneous or organic materials like leaves, roots, stems, cells, tissues and skin. Inorganic materials are also produced in biological systems. Bones, teeth, shells, nanomagnets inside the bodies of some bacteria and birds are some examples. Inorganic materials inside organic matter or organisms are known as biocomposites or biominerals. A variety of mechanically strong or weak, rigid or flexible, porous or nonporous, thick or thin materials either organic or inorganic in small or large quantities are abundantly produced in contact with live cells. These materials exhibit a wide variety in their functions like providing support to body, allow body movements and in general carry out various essential body functions. Table 5.1 gives a list of some biominerals produced or observed in the biological systems. The list is not at all complete and many more minerals are observed to be synthesized in nature under different environmental conditions. Many of the materials synthesized by microorganisms, animals and plants in nature can indeed be synthesized using them in laboratories even on large scale. This is considered to be a very attractive possibility so as to have eco-friendly or so-called green synthesis. Further the ability of bio-world to synthesize materials of variety of shapes and sizes is quite unique and often difficult to mimic, though not impossible.