## 3 Results and Discussions
### Xrd  
XRD was used to analyze the crystal structure of the ZS-ZnO-NPs synthesized using different zinc salts. Figure 6 shows the XRD patterns of the ZS-ZnO-NPs synthesized using different metal salts. The diffraction peaks observed in all samples at 20 (\({}^{\circ}\)) = 31.85, 34.46, 36.30, 47.59, 56.67, 62.89, 66.57, 68.1, and 69.10 were attributed to the crystallographic reflection's planes (100), (002), (101), (102), (110), (103), (200), (112), and (201), which corresponded to the characteristic peaks of the hexagonal wurtzite structure of ZnO (JCPDS n\({}^{\circ}\).01-079-2205) [68], confirming the successful synthesis of ZS-ZnO-NPs. The peak intensity and position exhibited variations depending on the type of zinc salt employed, particularly at the most intense peak (101) for each ZnO-NPs spectrum. ZS-ZnO-NPs synthesized with ZnCl\({}_{2}\) demonstrated superior crystallinity, showing a degree of crystallinity of 28.1% in Figure 6a. In comparison, ZnSO\({}_{4}\).H\({}_{2}\)O, Zn(CH\({}_{3}\)COO)\({}_{2}\).2H\({}_{2}\)O, and Zn(NO\({}_{3}\))\({}_{2}\).6H\({}_{2}\)O resulted in lower crystallinities at the same peak, with values of 27.6% (Figure 6b), 27.1%  
Figure 5: FFT illustrating the distinct crystalline structures of ZS-ZnO-NPs synthesized using different zinc salts and a plant extract of _Phoenix dactylifera_ L. at pH 12: (**a**). ZnCl\({}_{2}\), (**b**). ZnSO\({}_{4}\).H\({}_{2}\)O, (**c**). Zn(CH\({}_{3}\)COO)\({}_{2}\).2H\({}_{2}\)O, and (**d**). Zn(NO\({}_{3}\))\({}_{2}\).6H\({}_{2}\)O. (Figure 6c), and 14.8% (Figure 6d), respectively. The variation in peak intensities is likely attributed to differences in zinc ion concentrations and the nature of anions in the various zinc salts, impacting the growth and nucleation of ZS-ZnO-NPs [63; 69; 70]. This observation aligns with studies on the prolongation of oxidation time, where a similar effect in peak intensity and corresponding crystallinity was noted. This phenomenon was explained by the preferential growth of ZnO nanostructures along the c-axis as wet oxidation progressed from 2 to 8 h [71; 72]. When varying the anion, the application of the Hofmeister series can offer insights, as discussed in Section 3.3. The synthesis mechanism for the formation of zinc oxide nanoparticles (ZnO-NPs) using various zinc salts (ZnCl\({}_{2}\), ZnSO\({}_{4}\cdot\)H\({}_{2}\)O, Zn(CH\({}_{3}\)COO)\({}_{2}\cdot\)2H\({}_{2}\)O, and Zn(NO\({}_{3}\))\({}_{2}\cdot\)6H\({}_{2}\)O) and _Phoenix dactylifera_ L. extract involves a complex interplay of chemical reactions and molecular processes. The eco-friendly synthesis process is depicted in Figure 7, emphasizing the role of _Phoenix dactylifera_ L. extract as a rich source of polyphenols, which act as non-toxic antioxidants facilitating the reduction of metal precursors to ZnO-NPs. The use of polyphenols contributes to green synthesis by stabilizing the nanoparticles without generating toxic by-products, aligning with environmentally sustainable practices [19; 73; 74]. Figure 6: XRD spectra of ZS-ZnO-NPs synthesized using different zinc salts and a plant extract of _Phoenix dactylifera_ L. at pH 12: (**a**). ZnCl\({}_{2}\), (**b**). ZnSO\({}_{4}\cdot\)H\({}_{2}\)O, (**c**). Zn(CH\({}_{3}\)COO)\({}_{2}\cdot\)2H\({}_{2}\)O, and (**d**). Zn(NO\({}_{3}\))\({}_{2}\cdot\)6H\({}_{2}\)O. Standard ZnO diffraction pattern; JCPDS n\({}^{\circ}\)0.01-079-2205. The synthesis process can be delineated into three key phases [29, 75, 76]:  
1. Activation Phase: This initial phase involves precursor formation, metal ion reduction (neutralization reactions), and metal ion nucleation. The reduction of metal ions by phytochemicals, particularly polyphenols, plays a pivotal role in initiating the synthesis process. 2. Growth Phase: This phase is crucial for nanoparticle stability. The stabilized metal ions undergo further growth, contributing to the stability of the formed nanoparticles. 3. Termination Phase: In this phase, the shape of nanoparticles is determined.