Enhanced Self-Assembly of Pyridine-Capped CdSe Nanocrystals on Individual Single-Walled Carbon Nanotubes

We present a simple, noncovalent method for anchoring CdSe quantum dots (QDs) onto individual single-walled carbon nanotubes (SWNTs) through a ligand-exchange approach. Trioctylphosphine oxide (TOPO)-capped CdSe quantum dots were prepared, and the cap was then exchanged for pyridine (Py). It was found that the pyridine-capped quantum dots assembled much more effectively onto the SWNTs compared to the original TOPO-capped quantum dots. The density of the coverage of the quantum dots on the nanotubes was controlled through varying the concentration of the quantum dot solution and the reaction time. Spectroscopic studies indicated that the favorable formation of (Py-QD)−SWNT conjugates resulted from the π−π stacking interaction between the electron-rich SWNTs and the aromatic pyridine-capped quantum dots. Furthermore, the photoluminescence quenching of the quantum dots due to their interaction with the nanotubes suggests that the electron transfer from the quantum dots to the nanotubes was enhanced by using the pyridine cap.