Microwave‐Assisted Functionalization of Carbon Nanostructures in Ionic Liquids

Abstract

The effect of microwave (MW) irradiation and ionic liquids (IL) on the cycloaddition of azomethine ylides to [60]fullerene has been investigated by screening the reaction protocol with regard to the IL medium composition, the applied MW power, and the simultaneous cooling of the system. [60]Fullerene conversion up to 98 % is achieved in 2-10 min, by using a 1:3 mixture of the IL 1-methyl-3-n-octyl imidazolium tetrafluoroborate ([omim]BF(4)) and o-dichlorobenzene, and an applied power as low as 12 W. The mono- versus poly-addition selectivity to [60]fullerene can be tuned as a function of fullerene concentration. The reaction scope includes aliphatic, aromatic, and fluorous-tagged (FT) derivatives. MW irradiation of IL-structured bucky gels is instrumental for the functionalization of single-walled carbon nanotubes (SWNTs), yielding group coverages of up to one functional group per 60 carbon atoms of the SWNT network. An improved performance is obtained in low viscosity bucky gels, in the order [bmim]BF(4)> [omim]BF(4)> [hvim]TF(2)N (bmim=1-methyl-3-n-butyl imidazolium; hvim=1-vinyl-3-n-hexadecyl imidazolium). With this protocol, the introduction of fluorous-tagged pyrrolidine moieties onto the SWNT surface (1/108 functional coverage) yields novel FT-CNS (carbon nanostructures) with high affinity for fluorinated phases.

Effect of Surfactant Structure on Carbon Nanotube Sidewall Adsorption

“…[4] Moreover, CNT/polymer composites and CNT/ionic liquid gels have been considered for the preparation of actuator systems [5] and reaction media. [6] CNTs have been extensively explored for the development of highly sensitive and specific nanoscale biosensors. [2] Due to their intrinsic stability, structural flexibility and high aspect ratio, CNTs may act as highly efficient vehicles for the transport of a wide range of molecules across living cell membranes.…”

Non-covalent and reversible functionalization of carbon nanotubes

“…To date, several successful strategies have been applied to covalently derivatize CNTs sidewalls. Typical approaches include acid oxidation [25], cycloadditions spanning from the widely known 1,3-dipolar cycloaddition, namely the Prato reaction [26–28] to the Bingel [2 + 1] cyclopropanation [29], radical additions via diazonium salts [30–31] grafting of polymers. Nevertheless the creation of novel covalent bonds disrupt the sp 2 network of non-derivatized CNTs and may thus alter their inherent properties [30,32].…”

Green Processing of Carbon Nanomaterials

“…Zhang et al demonstrated a one-pot functionalization of a graphene sheet with porphyrin derivatives using a similar reaction. [49] The cycloaddition of azomethine ylides to fullerene under microwave irradiation was achieved within 10 min with conversion up to 98%. From the results of the luminescence lifetimes of materials, either energy or electron transfer between graphene and the covalently bonded porphyrins occurred after photoexcitation.…”