3. Analysis and result discussion

### 3.1 X-ray diffraction pattern study

XRD technique was used to investigate the crystallography structure phase and lattice parameters of the as-synthesized samples UZ and DZ (1.0 mol % Ag) NPs. Figure 2 depicts the intense and crystalline XRD patterns of the as-synthesized samples UZ and DZ (1.0 mol% Ag) NPs, which were registered at room temperature. All the diffraction peaks are indexed to the standard hexagonal wurtzite structure of ZnO NPs (inorganic crystal structure database number ICSD-52362). The sharpness of the broadened XRD diffraction peaks is an indication of the small size and the good crystallinity of the NPs, whereas the crystallinity of DZ (1.0 mol % Ag) NPs is better than UZ NPs. In addition, no peak corresponding to any impurity could be seen, and this confirms the formation of single phase of ZnO NPs. Moreover, no peak indicates the existence of other phase of Ag NPs. It was reported that no Ag peaks could be observed for 1% and 3% Ag concentrations; however, Ag peaks can still be detected in the XRD pattern of ZnO:5% Ag NPs [17]. Furthermore, XRD peaks related to Ag were presented in the samples calcined at 500, 700, and 900°C but disappear at 1100°C calcination temperature. This reveals that Ag atoms may have diffused in ZnO matrix. It can be noted that the preferred orientation corresponding to the plane (101), which overwhelms the other peaks, is the most prominent peak, which agrees with the results of Kumar et al. [18]. The XRD diffraction peaks are significantly broadened due to the small size of the NPs [19]. The calculated lattice parameters (a, c, and c/a) of samples UZ and DZ (1.0 mol% Ag) NPs are listed in Table 1. The calculated parameters match with the results of Xiaofeng Zhou et al. [20] and H. Zayed et al. [21]. Based on the Scherrer equation, the estimated average crystallite size (D) of the samples DZ and UZ NPs has been calculated from the highest diffraction peak along the (101) plane [22]:

$$\mathbf{D} = \frac{\mathbf{k} \,\lambda}{\mathfrak{B} \,\cos(\theta)}\tag{2}$$

where k is the particle shape factor (k = 0.9 for spherical particle), λ is the Cu-Kα X-ray wavelength (0.15418 nm), β is the full width at half maximum (FWHM) of XRD peaks, and θ is the Bragg angle corresponding to the same plane which obtained from the diffraction angle (2θ). The calculated values of D of the

Figure 2. X-ray diffraction patterns the samples UZ and DZ (1.0 Mol% Ag) NPs.


Table 1.

Geometric parameters of the samples UZ and DZ (1.0 mol% Ag) NPs.

samples UZ and DZ (1.0 mol% Ag) NPs are given in Table 1, which are 20.45 and 22.30 nm, respectively.
