Spatial photon confinement and super-radiation from dye cored dendrimer

Shiyoshi Yokoyama, Akira Otomo, Tatsuo Nakahama, Shinro Mashiko

This paper describes the preparation of a dendritic macromolecule having a rhodamine B chromophore, called Rh-dendrime,and the emission properties from the neat films due to the spontaneous emission and super-radiative emission. An important concept to be investigated for material preparation, is the surrounding of a fluorescent chromophore by the dendriticbranches.Therefore, a dendrimer becomes a core-shell structure, achieving a high efficiency of fluorescence with little energy transfer and self-quenching. The optical properties from dendrimer were very different from that of a bare chromophore. The Rh -dendrimer showed a high efficiency of fluorescence, while a bared rhodamine chromophore formed a charge transferred complex and exhibited less fluorescence. Under optical excitation with sufficient intensity (Io), theemission intensity was non-linearly increased as a function of the square of the number of molecules (N), giving relation of IaN2Io. This property cannot be adequately explained within the simple picture of spontaneous emission.Results were discussed in terms of cooperative emission.