Stability against degradation in solution was evaluated by heating X@Ag54 in toluene and tracking changes in its ultraviolet-visible (UV-vis) absorption spectrum. The results showed that 1) the stabilities of both clusters are similar, and 2) the absorption spectra of both samples in toluene can remain unchanged over 20 h of heating at 60 °C (Figures and). The half-life of both clusters under these degradation conditions was estimated to be approximately 200 h (Table ).