## 3 Results and Discussions  
### Process Efficiency  
Efficiency is an important parameter to consider when synthesizing nanoparticles (NPs) since it indicates the molar number of NPs successfully synthesized. In this case, ZS-ZnO-NPs were synthesized using different zinc salts as precursors in _Phoenix dactylifera_ L. extract, where the efficiency ranged from 48.0% to 55.3% (Figure 1). Zinc chloride (ZnCl\({}_{2}\)) and zinc sulfate (ZnSO\({}_{4}\cdot\)H\({}_{2}\)O) showed the highest efficiencies, with no significant difference between them. On the other hand, zinc acetate (Zn(CH\({}_{3}\)COO)\({}_{2}\cdot\)2H\({}_{2}\)O) exhibited the lowest efficiency at 48.0 \(\pm\) 0.3%, and zinc nitrate (Zn(NO\({}_{3}\))\({}_{2}\cdot\)6H\({}_{2}\)O) had an intermediate efficiency of 50.3 \(\pm\) 0.0% (Table 1). The physicochemical properties of the zinc salts used can affect the formation, size, surface charge, and morphology of NPs, leading to variations in efficiency. For instance, the highly soluble zinc chloride (4320 g/L of H\({}_{2}\)O at 25 \({}^{\circ}\)C [48]) may have contributed to the high efficiency of ZnO-NP synthesis by promoting rapid nucleation and crystal growth. In contrast, zinc acetate (40 g/L of H\({}_{2}\)O at 25 \({}^{\circ}\)C [49]) has lower solubility, which may have resulted in a slower reaction rate and lower efficiency. Zinc sulfate (965 g/L of H\({}_{2}\)O at room temperature [50]) and zinc nitrate have (1843 g/L of H\({}_{2}\)O at 20 \({}^{\circ}\)C) intermediate solubilities and may have contributed to the observed intermediate efficiency values for the latter case. \begin{table}
\begin{tabular}{c c c c c c c} \hline  & **Sample** & **Efficiency (\%)** & **Zeta Potential (mV)** & **D\({}_{\text{TEM}}\)** & **D\({}_{\text{SEM}}\)** & **Rod Length (nm)\({}_{\text{SEM}}\)** \\ \hline a & ZnCl\({}_{2}\) & 55.3 \(\pm\) 0.2 \({}^{\text{A}}\) & \(-\)46.7 \(\pm\) 0.5 \({}^{\text{A}}\) & 3.7 \(\pm\) 0.2 \({}^{\text{D}}\) & 6.4 \(\pm\) 1.7 \({}^{\text{D}}\) & 421.7 \(\pm\) 184.2 \({}^{\text{C}}\) \\ \hline b & ZnSO\({}_{4}\cdot\)H\({}_{2}\)O & 54.8 \(\pm\) 0.8 \({}^{\text{AB}}\) & \(-\)28.6 \(\pm\) 0.9 \({}^{\text{D}}\) & 6.6 \(\pm\) 0.1 \({}^{\text{C}}\) & 9.4 \(\pm\) 2.4 \({}^{\text{C}}\) & 473.7 \(\pm\) 184.8 \({}^{\text{BC}}\) \\ \hline c & Zn(CH\({}_{3}\)COO)\({}_{2}\cdot\)2H\({}_{2}\)O & 48.0 \(\pm\) 0.3 \({}^{\text{D}}\) & \(-\)32.5 \(\pm\) 1.0 \({}^{\text{C}}\) & 8.7 \(\pm\) 0.3 \({}^{\text{B}}\) & 14.7 \(\pm\) 2.5 \({}^{\text{B}}\) & 593.5 \(\pm\) 230.2 \({}^{\text{AB}}\) \\ \hline d & Zn(NO\({}_{3}\))\({}_{2}\cdot\)6H\({}_{2}\)O & 50.3 \(\pm\) 0.0 \({}^{\text{C}}\) & \(-\)41.5 \(\pm\) 0.1 \({}^{\text{B}}\) & 10.2 \(\pm\) 0.3 \({}^{\text{A}}\) & 19.6 \(\pm\) 2.5 \({}^{\text{A}}\) & 707.7 \(\pm\) 307.2 \({}^{\text{A}}\) \\ \hline \end{tabular} Note: “\(\pm\)” indicates the standard deviation, and lowercase letters (\({}^{\text{A}-\text{D}}\)) denote significant differences between samples based on statistical analysis.  
\end{table} 
Table 1: Results of efficiency (%), zeta potential (mV), diameter distribution average (nm) from TEM and SEM (D\({}_{\text{TEM}}\) and D\({}_{\text{SEM}}\), respectively), and rod length (nm) for 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.  
Figure 1: Process efficiency (%) of ZS-ZnO-NPs synthesis 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. The observed difference in efficiency between ZnSO4-H2O and Zn(NO3)2:6H2O prompts a closer examination of the influence of solubility on nanoparticle synthesis. While solubility is a critical factor, its impact is multifaceted.