The self-assembled structures by evaporation of tetrahydrofuran (THF) solut
ion of wire-type dendrimers have been studied by some spectroscopic and mic
roscopic techniques. Doughnut-like structures were obtained for some dendri
mers with generation number of 2 and about 28 nm length by depositions thei
r THF solutions on a quartz substrate, while yam-like and particle-like str
uctures were obtained for other dendrimers. The size of the doughnut struct
ure Varied from I to 8 mum in diameter and between 30 and 150 nm in height.
Confocal fluorescence microscopy, atomic force microscopy (AFM), and near-
field scanning optical microscopy (NSOM) were applied to elucidate assemble
d structures and electronic properties in addition to conventional fluoresc
ence spectroscopy. Polarization and local fluorescence measurements at some
parts of doughnuts and particles were demonstrated, however, no correlatio
n between molecular orientation/intermolecular interaction and doughnut str
uctures was found. The doughnut formation mechanism is considered on the ba
sis of evaporation processes observed from in situ experiments.