Plants do not produce silver (or any other metal) nanoparticles. They act as reducing agents for precursors such as ammoniacal silver nitrate. SPR gives rise to the characteristic peaks in the UV-VIS part of the spectrum (and thus to the color of the colloid/sol).

thank you...but how one can understand SPR Phenomenon here how these peaks are created in this range what is the exact cause?

Google (and Wikipedia) is your friend:

https://en.wikipedia.org/wiki/Surface_plasmon_resonance

In addition to Alan F Rawle .

The good explanations of SPR phenomen is presented in paper https://doi.org/10.1070/RC2008v077n03ABEH003751, some details are in our work too (https://doi.org/10.1201/b16895).

At the same time, the papers published by Dr. Naznin A. Begum (see https://www.researchgate.net/profile/Naznin_A_Begum) will be helpful for You. See, for example DOI:10.1007/s40097-016-0209-y; DOI:10.1016/j.ecoenv.2017.09.002.

Good luck!

Liliya

thank you mam