*2.2. Synthesis and Characterization of NMs*

The ZnNMs were synthesized using two different approaches: Wet chemical and Sol-gel synthesis methods. Six different ZnNMs samples were prepared using soluble zinc salts (zinc acetate/zinc nitrate/zinc chloride) as the precursors. The reducing/complexingcapping agents used in the study were sodium hydroxide [25], thiourea [26] and natural polymers such as starch [27,28], and cellulose-nanocomposite [29], and protein (Bovineserum albumin (BSA)) [30]. The brief protocols depicting the schematic steps have been provided in Figure 1.

**Figure 1.** Schematic representation of steps for the synthesis of zinc nanomaterials using different reducing and complexing/capping agents.

#### 2.2.1. UV-Vis Spectroscopy

The spectral absorbance behavior of the synthesized nanoparticles was analyzed on a Double Beam UV-Vis Spectrophotometer (model Elico SL 218, India) through screening over wavelengths ranging from 190 to 800 nm.

#### 2.2.2. Transmission Electron Microscopy

The morphology of the synthesized nanoparticles was determined by the transmission electron microscopy (Hitachi H-7650, Japan) analysis. The powdered ZnNMs were ground in a polystyrene pestle mortar, homogenized, and suspended in a known volume of deionized water. The suspension was bath sonicated for 15 to 30 min and 20 µL of the

suspension was then placed on a copper grid (carbon film-coated, 200-mesh size). The prepared grids were air-dried and viewed under high-resolution imaging mode in TEM operated at 80 kV acceleration voltage.
