Kefu Fu

Interactions of functionalized carbon nanotubes with tethered pyrenes in solution

Single-wall carbon nanotubes (SWNTs) were functionalized by oligomeric species containing derivatized pyrenes. Absorption and emission properties of the pyrene moieties tethered to the functionalized SWNTs were studied in homogeneous solution. The absorption spectra suggest no significant ground-state complexation between the pyrenes and nanotubes. The fluorescence and fluorescence excitation results show that the tethered pyrenes form “intramolecular” (intra-nanotube) excimers and that the excimer formation is predominantly dynamic in nature. The time-resolved fluorescence results show that the pyrene monomer and excimer emissions are significantly quenched by the attached SWNTs. The quenching is explained in terms of a mechanism in which carbon nanotubes serve as acceptors for excited-state energy transfers from the tethered pyrene moieties.

Functionalization of Carbon Nanotubes with Bovine Serum Albumin in Homogeneous Aqueous Solution

Single-walled (SWNTs) and multiple-walled (MWNTs) carbon nanotubes were solubilized via the esterification of nanotube-bound carboxylic acids by oligomeric polyethylene glycol compounds. The water-soluble samples were used as starting materials in reactions with bovine serum albumin (BSA) protein in ambient aqueous solutions. The reaction conditions were designed for thermodynamically favorable transformation from ester to amide linkages, yielding SWNT-BSA and MWNT-BSA conjugates. The results show that the use of soluble starting nanotube materials in an indirect functionalization method represents a valuable approach to the biomodification of carbon nanotubes.

Luminescence anisotropy of functionalized carbon nanotubes in solution

Luminescence anisotropy of functionalized single-wall (SWNT) and multiple-wall (MWNT) carbon nanotubes in solution and in polymeric thin-film matrix was investigated. The results show that the absorption and emission dipole moments are intrinsically collinear, corresponding to the limiting positive anisotropy. The observation of strong luminescence polarization for the functionalized carbon nanotubes in room-temperature chloroform is consistent with the polymeric nature of these luminescent species; and the partial depolarization in solution is rationalized in terms of the flexibility of the nanotubes.

Transparent silica glasses containing single walled carbon nanotubes

Organic/inorganic matrix nanocomposites have been created using an acid catalyzed, tetraethyl orthosilicate-based sol-gel technique with single-walled carbon nanotubes (SWNTs). By utilizing nanotubes functionalized with the dendron methyl 3,5-di(methyltrigycoloxy)benzylic alcohol (IPEG), ultrasonic blending in the sol phase prior to gelation yields excellent dispersion characteristics of the nanotube phase. The glasses were densified by heating to 600 °C yielding 80% of theoretical density with little change in the optical appearance or behavior. These materials exhibited intrinsic Rayleigh scattering, suggesting near ideal dispersion. Nonlinear optical transmission was observed for 1064 and 532 nm light suggesting that the matrix has a strong broad band coupling to the optical field. Such composites allow for a host of applications based on the novel confinement properties of carbon nanotubes in a robust inorganic host.

Efficient intramolecular excited-state energy transfer in pyrenes–fullerene macromolecule

The fluorescence of pyrene species covalently linked with a methanofullerene is nearly completely quenched due to efficient excited-state energy transfer to the fullerene cage, resulting in the population of the emissive fullerene excited state. The quenching is largely static in nature, consistent with the computational result that the pyrene moieties are close to the fullerene cage. The yield for the excited-state pyrene to fullerene energy transfer is determined.

Interesting fluorescence properties of C60-centered dendritic adduct with twelve symmetrically attached pyrenes

A C60-centered dendritic adduct with 12 symmetrically attached pyrene species was synthesized and found to have relatively simple fluorescence emission kinetics, in particular, the mono-exponential decay of the significant pyrene excimer emission.

Transparent silica glasses containing single-walled carbon nanotubes

Organic - Inorganic matrix nano composites have been created using an acid catalyzed, tetraethyl orthosilicate-based sol- gel technique with SWNTs. By utilizing nanotubes functionalized with the dendron methyl 3,5- di(methyltrigycoloxy)benzylic alcohol, ultrasonication blending in the sol phase prior to gelation yields excellent dispersion characteristics of the nanotube phase. Further, glasses could easily be dried by heating to 600 degrees C yielding 80 percent of theoretical density wit little change in the nanotube content. These materials exhibited intrinsic Rayleigh scattering, suggesting near ideal dispersion. Nonlinear optical transmissivity was observed for 1064 and 532 nm light suggesting that the matrix has a strong broad band coupling to the optical field. Such composites allow for a host of applications based on the novel confinement properties of carbon nanotubes in a robust host.