**3.2 Characterization of silver nanoparticles**

#### *3.2.1 UV-Vis spectrometry*

The UV-visual spectra of the synthesized nanoparticles were recorded by a UV-Vis spectrophotometer. The developed color was examined at 220–600 nm in a UV-Vis spectrophotometer (Lambda 25 UV/Vis, Perkin Elmer, Shelton, CT, USA).

#### *3.2.2 Fourier transformer infra-red spectrometry (FT-IR)*

The FTIR spectra were measured using Thermonicolet Spectrometer, Nexus 870, Thermo Nicolet, Madison, USA instrument. The synthesized green silver nanoparticle was obtained from maximum biomass culture and was pressed into KBr pellets at a ratio of 1:100. The spectra were then recorded in transmittance mode over the wave range of 4000–400 cm−1.

#### *3.2.3 X-ray diffraction analysis*

The XRD analysis of the sample was collected at room temperature on a Philips X'Pert Pro diffractometer, equipped with a Cu target X-ray tube with a step size of 0.020, 2θ, and time per step of 0.3 s.

The methods of Williamson and Hall were used to calculate the crystal size and strain. The simplest and most widely used method for estimating the mean crystal size is from the full width at half peak (FWHM) of the diffraction peak using the Scherrer equation as follows:

$$\mathbf{d}\_{\rm XRD} = \mathbf{K}\mathcal{X} / \mathbf{B}\cos\theta \,\tag{1}$$

Where d is the crystal size, λ diffraction wavelength, B is the corrected FWHM, is the diffraction angle, and K is the near-unit constant. The main assumption is that the sample is not deformed. B can be obtained from the observed FWHM by complicating a Gaussian configuration that models the expansion of the Br pattern, like this:

$$\mathbf{B}^2 \mathbf{r} = \mathbf{B}^2 \mathbf{o} - \mathbf{B}^2 \tag{2}$$

Where B0 is widely observed, and Bi is the instrument broadening. Williamson and Hall is a simplified integral width method to decipher the contributions of size and strain to line expansion as a function of 2θ [20].
