A facile strategy for preparation of fluorescent SWNT complexes With high quantum yields based on ion exchange

The fluorescent imidazolium salt (1,3-bis(9-anthracenylmethyl)imidazolium chloride, [bamim]Cl) has been grafted onto the surfaces of single-walled carbon nanotubes (SWNTs) using an ion exchange strategy based on metathesis of the K+ ion in CO2K derivatized SWNTs with [bamim]+. The resulting SWNT-[bamim] complex has been characterized with high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), elemental mapping, and elemental linear profiles analysis. A blue light emission can be observed at 392,414 and 438 nm for SWNT-[bamim] upon being excited at 254nm. The quantum yield (QY) of the SWNT-[bamim] complex (0.40) is much higher than that of SWNT/[bamim]Cl (0.02), used as a control, and prepared using a pi-pi stacking method, indicating that ion exchange is a far more effective strategy for retaining a high QY. Additionally, UV-Vis-NIR and Raman spectroscopy show that the SWNT-[bamim] complex can maintain the one-dimensional electronic states of SWNTs. Other imidazolium salts have also been successfully grafted onto SWNTs via the same strategy, indicating that the ion exchange process can serve as a universal strategy for the functionalization of SWNTs.