**3.4 Nature of silver nanoparticles**

Due to their application intent, colloidal nature of the synthesized silver nanoparticles is a critical aspect to consider. If the silver nanoparticles are not stabilized, they become heavy and will be found at bottom of flask or beaker. This aggregation problems can be resolved by sonicating the silver nanoparticle solution as well as using NaCl salt which hides the charges allowing the particles to clump together to form aggregates. Generally, a peak around 420–460 nm confirms stable silver nanoparticle synthesis, while silver nanoparticle aggregates form a broad peak around 350–525 nm with a decrease in the intensity of the plasmon absorbance [19].

### **Figure 2.**

*General optimization method, criteria, instrument characterization and potential applications of synthesized nanoparticles [18].*

**Figure 3.** *Complete process of green synthesis of silver nanoparticles at room temperature [18].*
