C60-Fullerene in Water Solution, γ-Cyclodextrin Complex and Cluster of C60: An NMR and a Photophysical Study
γ-CD has been used to dissolve C60 in water. At high γ-CD:C60 ratio a complex that is monomeric in C60 is stable whereas at lower γ-CD:C60 ratio a cluster of several C60 molecules surrounded by γ-CD is stable. We propose that clusters of different sizes can be formed. The γ-CD:C60 complex have an electronic absorption spectrum similar to that of an organic solution of C60 and the cluster have an electronic absorption spectrum similar to that of a thin film of C60. In an NMR experiment on a γ-CD.C60 complex solution two sets of signals for me cyclodextrin protons were observed indicating that the exchange of C60 between different γ-CD:s is slow on the NMR time scale.
For the γ-CD:C60 complex, the photophysical properties are similar to those of C60 in an organic solvent with the exceptions for quenching rates of the triplet state by molecular oxygen and annihilation rates of the triplet state.
The properties of the clusters are different from those of an organic solution of monomeric C60. For water solutions of small clusters, decay of the excited state of the cluster is clearly dependent on the intensity of the excitation laser pulse; at high laser intensity there is both a fast and a slow component in the decay process whereas at low laser intensity only the slow process is observed.
KeywordsToluene Half Life Fullerene Cyclodextrin
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