Understanding the chemistry of single-walled carbon nanotubes (SWNTs) is critical to rational manipulation of their properties. In one set of experiments, raw and oxidized SWNTs have been reacted with metal-containing molecular complexes.
One of the molecular complexes studied was Vaska's compound. It has been found that Ir coordinates to these nanotubes by two distinctive pathways. With raw nanotubes, the metal attaches as if the tubes behaved as electron-deficient alkenes. With oxidized nanotubes, the reaction occurs by coordination through the increased number of oxygen atoms, forming a hexacoordinate structure around the Ir atom. Another compound analyzed was Wilkinson's complex. It has been found that the Rh metal similarly coordinates to these nanotubes through the increased number of oxygenated species. The adducts of SWNTs with these complexes have been structurally characterized by electron and atomic force microscopy. Optical properties have been extensively probed by means of UV-Vis-NIR, mass, and multinuclear NMR spectroscopy as well as by photoluminescence studies. The functionalization reaction, in general, appears to significantly increase oxidized nanotube solubility in DMF (in the case of Vaska's) and in DMSO (with Wilkinson's). The derivatization process results in exfoliation of larger bundles of SWNTs and may select for the presence of distributions of smaller diameter tubes. An application has been made of this system as supports for homogeneous catalysis.
In another set of experiments, oxidized SWNTs have been reacted with cadmium selenide nanocrystals (quantum dots) as well as with titanium dioxide nanocrystals to form nanoscale heterostructures, characterized by transmission electron microscopy and infrared spectroscopy. Based on the types of intermediary linking agents used, we have demonstrated a level of control over the spatial distribution of nanocrystals on these tubes. Optical data on the derivatized adducts suggest the possibility of interesting charge transfer behavior across the nanocrystal-nanotube interface. Such composites are expected to be useful for applications as diverse as molecular electronics, photocatalysis, solar energy conversion, and as probes for scanning force microscopy.
Sarbajit Banerjee and Stanislaus S. Wong, Synthesis and Characterization of Carbon Nanotube-Nanocrystal Heterostructures, Nano Letters, 2(3), 195-200 (2002).
Sarbajit Banerjee and Stanislaus S. Wong, Functionalization of Carbon Nanotubes with a Metal-Containing Molecular Complex, Nano Letters, 2(1), 49-53 (2002).
Stanislaus S. Wong
Department of Chemistry, State University of New York at Stony Brook
Stony Brook, NY 11794 USA
Phone: 631-632-1703 Fax: 631-632-7960