| Abstract
| - Gold nanocrystals in a toluene solution were aggregated by several thiophene and pyrrole oligomers as shownby surface plasmon (SP) spectroscopy and TEM analysis. The rate of aggregation can be controlled by varyingthe oligomer type and concentration. Two distinct regimes of aggregation kinetics are observed: (1) at lowoligomer concentrations, aggregation is slow and dependent on the gold nanocrystal concentration withproduction of a SP band at ca. 700 nm and (2) at high oligomer concentrations, aggregation is very fast andproduces a SP band at ca. 570 nm. The results suggest that, in general, at high oligomer concentrations, thelinker molecules form more dense layers via perpendicular orientation toward the metal plane, whereas aparallel orientation is obtained at low concentrations. TEM analysis indicates in the high concentration regimethat there is formation of spherical or dendritic superclusters depending on the aggregating oligomer. FTIRanalysis of the terthiophene and dipyrrole gold aggregates has shown the presence of adsorbed ligand moleculeswith surface enhancements of some bands, giving features particular to parallel and perpendicular coordination,respectively.
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