Quantum dots of SnI4 and its clusters in cyclodextrins

From the reflection spectra of tin tetraiodide (SnI4) single crystals, the exciton absorption band has been observed at peak energies of 3.14 eV (77 K) and 3.07 eV (room temperature). The exciton binding energy is estimated at 380 meV. The large binding energy suggests that each SnI4 molecule has a quantum dot-like character. The reflection spectra of the SnI4 clusters in γ-cyclodextrins were also measured. The first exciton peak of the clusters shift to a higher energy by 0.35 eV (77 K) and 0.40 eV (room temperature) compared with those of the single crystal due to the quantum size effect.