**5.4 Silver nitrate (AgNO3) concentration**

The concentration of AgNO3 is measured in a range of 0.1–1 mM or even more concentrations, such as 10, 50 and 100 mM [22]. However, 1 mM concentration is best studied and suggested as we are actually synthesizing nanoparticles that are very minute and cannot be seen with naked eyes. Therefore, a very small quantity of the reactant is required for the reaction to occur. If the concentration of the reactant is increased, the reduction of Ag++ will not be successful and the accumulation could be noticeable. Actually, it does not make sense to use higher concentration for synthesis of nanoscale particles. Another factor vital for synthesis is the reaction stirring time for up to which reaction mixture is stirred.

#### **5.5 Reaction stirring time**

The reaction stirring time is the time required for silver nanoparticle synthesis starting from the reactant is added in the beaker to occur reaction. The stirring time will enable the proper interaction of silver salt with the reducing complex components present in test leaf extract. The plant containing the more secondary metabolites or phytochemicals will reduce the silver salt in less time, in other terms the plant containing fewer reduced compounds will take longer time for reducing silver salt. However, the less number of secondary metabolites reduces silver salt and nanoparticles formed quickly in very less time. The stirring time will be dependent on reaction mixture acidity, basicity, temperature, reducing power of extract, light intensity, enzyme and secondary metabolites of the test plant extract. Ref. [23] concluded that the stability of silver nanoparticle synthesis using glutathione as a reducing agent increases at 72 h and confirms the visible UV absorbance at 344–354 nm. Thus stirring time affects the synthesis of nanoparticles, the duration of the synthesis of nanoparticles, the time allowed for the interaction of silver nitrate and leaf extract.
