**4.1 General synthesis process**

In brief, the reactant, that is, plant extract and the AgNO3 (1 mM) are mixed in a specific ratio such as 95:5 ml, respectively, and the reaction is conducted under specific instrument or machine, such as early mention of microwave oven, autoclave, sonication, heating, boiling, etc. During a study of these methods or conditions, the size or shape and type or form of nanoparticles formulated depend upon the kinetics of reaction that relays on the adopted methodology. In this section, we addressed different conditions under which nanoparticles could be generated. For example, the effect on the synthesis of nanoparticles of a specific sound wave may differ from that of light intensity or color. The sunlight has a specific effect on nanoparticle synthesis, which synthesizes nanoparticles of different sizes and shapes.

**101**

*Phytonanofabrication: Methodology and Factors Affecting Biosynthesis of Nanoparticles*

The microwave oven that could be used for synthesis of nanoparticles is one of the popular techniques. The microwave oven is a method for the processing of nanoparticles using different intensities of microwave radiation. Here the reactant, which may be a capping agent, is mixed with metallic salts and the mixture is placed in a microwave oven. Microwave treatment is administered to the reaction mixture in a short burst of 20 s for 5 min, which has influenced the kinetics of the mixture and drastically alters the size and shape of the nanoparticles. The radio wave in microwave oven is utilized to activate compounds or secondary metabolites in extract to reduce metal salts. Radio wave at a specific frequency is absorbed by extract components (phytochemicals and secondary metabolites) or activates certain extract enzymes to reduce metallic salts for stable nanoparticle production. As a result, microwave oven-assisted silver nanoparticles form in less time and are

The basic instrument used in the laboratory is an autoclave that produces steam at a pressure of 50 psi and reaches a temperature of ~121°C, at which organisms, pathogens and even endospores are killed or destroyed within 15 min. However, nanotechnologists use autoclaves to create a specific pressure and temperature for nanoparticle synthesis. In this process, kinetic of mixture is influenced by autoclave which is preheated for 5 min, once the pressure rises the flap is opened and the mixture flask or round bottom flask is kept in it for 5 min. Autoclave is not allowed to achieve 50 psi, instead, the autoclave is preheated to 5–10 psi for nanoparticle synthesis, and capping agent and the reducing agent are mixed with metallic salt and kept inside the autoclave for a specific time. Care must be taken in this method, as the autoclave is a very simple but dangerous machine, if the pressure rises above the crucial level and when it is opened critically results in steam or blast. Similarly, sonication is another way that could be used to synthesize nanoparticles [18].

Sonication produces excitation of compounds from various biological sources, such as plants, microbes, animals, extracts, etc. It uses sound energy to agitate metallic salt in a reaction mixture (AgNO3 + plant extract) to form nanoparticles. The specific wave hertz (Hz) is adjusted and applied to the reaction mixture for a specific time and the synthesized silver nanoparticles can be easily collected. Typically, an ultrasonic frequency of 20 kHz is administered to the reaction mixture. It is also referred to as ultrasound used for the synthesis of nanoparticles, nanoemulsions, nanocrystals and other forms. In addition, sonication is used for dispensing nanoparticles in liquid solution to disaggregate larger nanoparticles. Similar to sonication heating, the reaction mixture could also be another method for synthesis of nanoparticles [18].

In the heating process, heat energy is transferred to and from the mixture of extract and silver salt. Thus, when the reactants are heated, the heat excites the electron of the reacting secondary metabolites as well as the Ag2+ ions, the NO3

ion silver salts to reduce Ag2+ ions to form Ag zero valent. In specific, the reaction

2−

*DOI: http://dx.doi.org/10.5772/intechopen.90918*

therefore the fastest way to synthesize [18].

**4.2 Various methods**

*4.2.1 Microwave oven*

*4.2.2 Autoclave*

*4.2.3 Sonication*

*4.2.4 Heating*

*Phytonanofabrication: Methodology and Factors Affecting Biosynthesis of Nanoparticles DOI: http://dx.doi.org/10.5772/intechopen.90918*
