ABSTRACT
The properties of nanostructure or nanocluster materials are vastly different from those of bulk materials, which is their most noticeable characteristic. A high surface area to volume ratio is one of the key factors in influencing their properties. As a result, adjusting the size and shape of nanomaterials according to needs might result in innovative design. For the synthesis of nanomaterials, two methods—top-down and bottom-up—are frequently used. Top-down methods need a lot of energy and are ineffective for synthesizing nanoparticles using biological agents. In most chemical processes, using a bottom-up strategy, synthetic chemicals are required to produce metal nanoparticles.
Although chemical synthesis techniques have several benefits for regulating the size, shape, and surface morphology of nanoparticles, they frequently include toxic chemicals that may release dangerous byproducts or precursor compounds into the environment. The synthesis of nanoparticles using biological agents, such as microorganisms and plant extracts, has some benefits, including availability, cost-effectiveness, non-toxic chemical precursors, ecologically acceptable products, and by-products. The employment of microbes or microorganisms is one of the most prominent approaches to biological methods of nanoparticle synthesis, particularly for the extracellular and intracellular formation of noble metal nanoparticles. Many studies have revealed that various functional groups of microbial proteins (such as -NH2, -OH, -SH, and -COOH) act as important reducing or capping agents during the formation of metal nanoparticles. Plant extracts are a complex mixture of biochemicals, such as polysaccharides, proteins, amino acids, organic acids, polyphenols, flavonoids, terpenoids, alkaloids, tannins, and alcoholic compounds that can reduce metal ions and stabilize metal nanoparticles. An emerging field of nanotechnology is the use of metal nanoparticles against plant diseases. An organism (such as bacteria, fungi, protists, nematodes, and viruses) that causes disease in a plant is known as a plant pathogen. The biosynthesized metal nanoparticles showed strong antibacterial activity against various plant diseases. This chapter discusses the synthesis of noble metal nanoparticles using a range of biological agents such as bacteria, fungi, and plants. The use of biosynthesized nanoparticles against plant pathogens is discussed.
