**5. Application areas of nanoparticles**

Generally, nanoparticles have been applied in various areas including anticancer drugs, vaccines, disease treatment, cancer diagnosis, mechanical factories, electronics, optical devices, energy harvesters, manufacturing processes, cell imaging, and delivery systems due to their unique features [4]. NPs also aid water contaminants to be absorbed on the surface during water purification, serve as environmental sensors, and protect materials from harmful substances. Some of the application areas of the nanoparticles [2, 23] have been summarized in **Table 2**.

Despite the numerous applications of NPs; they suffer from poisonous and harmful body effects which inhaled, ingested, or transferred to the ground and surrounding environs. Nanoparticles are also affected by organic materials which lead to agglomeration. The poisonous effects associated with NP synthesis can be curtailed by adopting green synthesis methods especially in the synthesis of silver,


### **Table 2.**

*Application areas of some nanoparticles.*

iron, copper, gold nanoparticles amongst others [25]. The synthesis process for silver nanoparticles is as shown in **Figure 4** [25].

Green synthesis involves different capping substances like biomolecules and polysaccharides. Green methods are non-poisonous, environmentally friendly, involve toxic-free solvents, compatible in biological systems, and utilize reagents like sugars, polymers, vitamins, plant extracts [26]. Plant-based extracts like latex, leaf, seed, root, or stem are more suited for bioprocesses as they are cheap, noncomplex, easily reproduced, and highly stable. Other sources of waste materials useful for nanoparticle production have been outlined in **Figure 5**. Models can be developed to minimize the difficulties associated with distributing the size of the particles and NPs synthesis by computing the rates at which the particles get nucleated [11].

**Figure 4.**

*Experimental diagram for the bioproduction of silver nanoparticles.*

**Figure 5.** *Schematic showing different sources of waste material.*
