# Enhancing Methyl Orange Degradation with Laser-Generated ZnO and Ce-Doped ZnO Nanoparticles
## 3 Results and Discussion
### Photocatalytic Degradation of MO Dye
Figure 7: Degradation efficiencies of MO dye by **(a)** 1% Ce/ZnO NPs and **(b)** ZnO NPs before and after annealing in the dark (**left**) and under UV and solar light (**right**). attributed to the annealing process, which enhances crystallization and other physical properties [42]. Additionally, the increased concentration of electron acceptors (Ce\({}^{4+}\) ions) and oxygen vacancies, combined with precise doping with respect to Ce\({}^{4+}\) ions in the ZnO nanostructure, contributes to the increased photocatalytic activity. Moreover, the presence of Ce\({}^{4+}\) on the surface of ZnO NPs plays a crucial role in facilitating interfacial charge transfer and suppressing electron-hole recombination. As a result, Ce\({}^{4+}\) may act as an electron scavenger during the degradation of the MO dye [27]. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{3}{*}{**Sample**} & \multicolumn{4}{c}{**UV**} & \multicolumn{4}{c}{**SUN**} \\ \cline{2-9}  & \multicolumn{2}{c}{**before**} & \multicolumn{2}{c}{**after**} & \multicolumn{2}{c}{**before**} & \multicolumn{2}{c}{**after**} \\ \cline{2-9}  & \(k\) & \(\textbf{(min^{-1})}\) & \(R^{2}\) & \(\textbf{(min^{-1})}\) & \(R^{2}\) & \(\textbf{(min^{-1})}\) & \(R^{2}\) & \(\textbf{(min^{-1})}\) & \(R^{2}\) \\ \hline ZnO NPs & 0.00404 & 0.70887 & 0.00417 & 0.81617 & 0.00672 & 0.78996 & 0.00663 & 0.84083 \\ \hline \multicolumn{9}{l}{1\% Ce-doped} \\ ZnO NPs & 0.0079 & 0.86034 & 0.01508 & 0.95236 & 0.0101 & 0.92149 & 0.0271 & 0.98526 \\ \hline \multirow{3}{*}{ZnO NPs} & \(\textbf{\emph{q}_{e}}\) & \(\textbf{\emph{q}_{t}}\) & \(\textbf{\emph{q}_{e}}\) & \(\textbf{\emph{q}_{t}}\) & \(\textbf{\emph{q}_{e}}\) & \(\textbf{\emph{q}_{t}}\) & \(\textbf{\emph{q}_{e}}\) & \(\textbf{\emph{q}_{t}}\) \\ \cline{2-9}  & \(\textbf{(mg\cdot g^{-1})}\) & \(\textbf{(mg\cdot g^{-1})}\) & \(\textbf{(mg\cdot g^{-1})}\) & \(\textbf{(mg\cdot g^{-1})}\) & \(\textbf{(mg\cdot g^{-1})}\) & \(\textbf{(mg\cdot g^{-1})}\) & \(\textbf{(mg\cdot g^{-1})}\) & \(\textbf{(mg\cdot g^{-1})}\) \\ \hline \multicolumn{9}{l}{ZnO NPs} & 15.1663 & 17.2983 & 15.2951 & 17.0564 & 15.6168 & 18.1426 & 15.6598 & 17.8561 \\ \hline \multicolumn{9}{l}{1\% Ce-doped} \\ ZnO NPs & 17.5743 & 16.0498 & 17.1596 & 17.1226 & 17.5369 & 17.0119 & 17.5528 & 18.0999 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Rate constants (\(k\) min\({}^{-1}\)) with linear regressions (\(R^{2}\)) for ZnO NPs and 1% Ce/ZnO NPs before and after annealing. Figure 8: Efficiency of relative concentrations of MO molecules photodegradation for **(a)** 1% Ce/ZnO NPs and **(b)** ZnO NPs; concentration decay of MO in logarithmic scale for **(c)** 1% Ce/ZnO NPs and **(d)** ZnO NPs (before and after annealing) under UV and solar light. As observed from Figure 9, under optimized conditions, adsorption reaches equilibrium within 30 min for both 1% Ce-doped ZnO NPs and undoped ZnO, both before and after annealing. The adsorption capacity remains nearly consistent across all cases. Notably, 1% Ce-doped ZnO NPs exhibit higher adsorption capacities in the absence of light (dark conditions). Upon irradiation, their degradation performance is significantly enhanced, leading to complete photodegradation of MO within 90 min, both before and after annealing.