## 3 Results and Discussions
### Antioxidant Activity  
The synthesized ZS-ZnO-NPs were evaluated for their antioxidant activity using the DPPH FR\({}^{\bullet}\) assay. A series of experiments were performed with different concentrations (50-1000 ug/mL, Table 3) and incubation times (0.5-24 h, Table 3) to fully understand this property. The results, as shown in Figure 10 (Table 3), demonstrated that all ZS-ZnO-NPs exhibited antioxidant activity, and there was an increase in antioxidant activity with increasing concentration and incubation time. Figure 10: Concentration-dependent (50, 125, 250, 500, and 1000 ug/mL) and time-dependent (0.5, 3, 6, 12, and 24 h) trends in antioxidant activity (_IP_ % DPPH inhibition) of ZS-ZnO-NPs synthesized using different zinc salts and a plant extract of _Phoeenix 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. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c c c c c c c c} \hline \hline \multicolumn{11}{c}{**IP (\%)**} \\ \hline \multicolumn{11}{c}{**Time (h)**} & \multicolumn{4}{c}{**0.5**} & \multicolumn{4}{c}{**3**} & \multicolumn{4}{c}{**6**} & \multicolumn{4}{c}{**12**} & \multicolumn{4}{c}{**24**} \\ \hline C (\(\mu\)g/mL) & **a** & **b** & **c** & **d** & **a** & **b** & **c** & **d** & **a** & **b** & **c** & **d** & **a** & **b** & **c** & **d** & **a** & **b** & **c** & **d** \\ \hline
50 & 33.9 & 37.2 & 35.8 & 26.1 & 41.2 & 47.9 & 42.8 & 36.4 & 48.2 & 56.4 & 49.5 & 43.7 & 56.7 & 68.3 & 59.3 & 52.3 & 64.8 & 79.1 & 68.6 & 64.9 \\
125 & 47.7 & 50.6 & 48.5 & 34.2 & 56.9 & 63.7 & 59.6 & 47.6 & 64.6 & 71.6 & 67.8 & 54.9 & 70.6 & 80.1 & 74.8 & 65.7 & 93.2 & 94.3 & 95.2 & 72.3 \\
250 & 61.4 & 62.4 & 59.8 & 45.8 & 73.2 & 75.1 & 69.8 & 59.1 & 78.6 & 82.5 & 75.8 & 68.1 & 85.8 & 88.2 & 82.5 & 78.5 & 97.5 & 99.1 & 98.8 & 90.5 \\
500 & 73.1 & 74.3 & 69.7 & 57.3 & 78.5 & 79.2 & 75.6 & 70.8 & 85.2 & 86.2 & 81.2 & 79.5 & 90.8 & 91.3 & 86.9 & 85.6 & 98.4 & 99.7 & 99.2 & 94.6 \\
1000 & 77.5 & 78.3 & 73.9 & 68.5 & 81.7 & 83.1 & 78.6 & 76.9 & 88.1 & 88.9 & 84.6 & 84.6 & 92.7 & 93.2 & 89.3 & 89.2 & 99.1 & 99.8 & 99.3 & 97.4 \\ \hline \hline \end{tabular} Note: Rows with the same values in the time column for a given concentration indicate no significant difference in antioxidant activity (IP% DPPH inhibition) between the corresponding time points.  
\end{table} 
Table 3: Concentration-dependent (50, 125, 250, 500, and 1000 ug/mL) and time-dependent (0.5, 3, 6, 12, and 24 h) trends in antioxidant activity (IP% DPPH inhibition) of ZS-ZnO-NPs synthesized using different zinc salts and a plant extract of _Phoeenix 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. Specifically, ZS-ZnO-NPs synthesized using ZnSO\({}_{4}\cdot\)H\({}_{2}\)O exhibited the highest scavenging activity among all the tested concentrations and incubation times, with inhibition percentages ranging from 37.2% to 78.3% at 50-1000 \(\upmu\)g/mL after 0.5 h of incubation. ZnCl\({}_{2}\) showed 77.5% inhibition at 1000 \(\upmu\)g/mL after 0.5 h of incubation, followed by Zn(CH\({}_{3}\)COO)\({}_{2}\cdot\)2H\({}_{2}\)O with 73.9% inhibition at 1000 \(\upmu\)g/mL after 0.5 h of incubation and Zn(NO\({}_{3}\))\({}_{2}\cdot\)6H2O with 68.5% inhibition. The antioxidant activity of the ZS-ZnO-NPs was found to be concentration-dependent, with higher concentrations resulting in higher antioxidant activity. This could be due to the increased availability of ZS-ZnO-NPs to scavenge free radicals at higher concentrations. Moreover, the antioxidant activity of ZS-ZnO-NPs also increased with increasing the concentration and incubation time up to a certain point, beyond which the activity plateaued.