Synthesis and characterization of carbon nanotube-nanocrystal heterostructures

Oxidized single-walled carbon nanotubes (SWNTs) have been reacted with cadmium selenide (CdSe) nanocrystals, capped with mercaptothiol derivatives, as well as with titanium dioxide (TiO2) nanocrystals, functionalized with 11-aminoundecanoic acid to form nanoscale heterostructures, characterized by transmission electron microscopy and infrared spectroscopy. The reaction with acid-terminated CdSe nanocrystals and acid-terminated tubes was facilitated with the aid of intermediary linking agents, such as ethylenediamine and semicarbazide, in an amide-forming reaction in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride, EDC. Based on electronic absorption spectroscopy, charge transfer is thought to proceed from the nanocrystal to the nanotube in the CdSe-nanotube system, whereas in the TiO2-nanotube system, charge transfer is expected to occur from the nanotube to the nanocrystal.