The acid catalyst is generally needed to assist the formation of gel. In our tests, without the acid catalyst, the TEOS glassy solution did not show any sign of gelation within several days. However, to our surprise, significant gel formation was observed when the QDs were mixed into the glassy solution ( sol), even in absence of the acid catalyst. Fluorescence result further showed a clear QD emission peak, indicating that the QDs were successfully embedded into the glass. Since the commercial QDs used in these tests were suspended in a toluene solution with the help of ODA ligands, to understand which factor plays the key role in the gel formation, we added powdered QDs (with minimal ODA attached), ODA ligands, and toluene to separate glassy solutions. The solution with the ODA ligands showed a gelation process similar to the earlier observation with ODA-suspended QDs, indicating the ODA ligands can indeed assist the formation of the gel, which is also consistent with some prior reports.11,12 To further verify this finding, we measured the gelation time of glassy solutions with different ODA concentrations. The result shows that higher ODA concentrations result in quicker gelation (see Fig. 2), indicating a direct correlation between gel formation and the presence of ODA.