Hybrid CdSe Nanoparticle-Carbazole Dendron Boxes : Electropolymerization and Energy-Transfer Mechanism Shift

Carbazole containing ligand dendrons are designed based on second generation polybenzyl ether dendrons (2GPO). This is subsequently used for directly synthesizing and capping CdSe nanoparticles in contrast to ligand exchange for introducing functionality. The stable hybrid CdSe-2GPO quantum dot nanoparticles have characteristic energy-transfer properties from the donor carbazole peripheral groups to the acceptor CdSe nanoparticles, i.e., overlap of the fluorescence of the carbazole with the absorbance of the CdSe nanoparticle resulting in an enhanced fluorescence with concentration through Forster resonance energy transfer (FRET). However, electropolymerization of the peripheral electroactive carbazole units result in a red-shift in absorbance and quenching in fluorescence. This is attributed to a reversed molecular orbital energy order with respect to the electropolymerized carbazole dendron and CdSe nanoparticle. The hole-transfer results in fluoresence quenching and charge transfer between the CdSe nanoparticles and the polycarbazole peripheral units. The photoelectric alteration may yet provide for an interesting electro-optical or sensing device application based on electrochemical properties of the hybrid material.