Spectroscopic properties of nanotube-chromophore hybrids.

Recently, individual single-walled carbon nanotubes (SWNTs) functionalized with azo-benzene chromophores were shown to form a new class of hybrid nanomaterials for optoelectronics applications. Here we use a number of experimental and computational techniques to understand the binding, orientation, and nature of coupling between chromophores and the nanotubes, all of which are relevant to future optimization of these hybrid materials. We find that the binding energy between chromophores and nanotubes depends strongly on the type of tether that is used to bind the chromophores to the nanotubes.

Solvatochromic shifts of single-walled carbon nanotubes in nonpolar microenvironments.

Single-walled carbon nanotubes (SWNTs) are encapsulated with microenvironments of nonpolar solvent, providing a new method to measure the photophysical properties of nanotubes in environments with known properties. Photoluminescence (PL) and absorbance spectra of SWNTs show solvatochromic shifts in 16 nonpolar solvents, which are proportional to the solvent induction polarization. The shifts in the emission energies (DeltaE(11)) range from approximately 25 to 100 meV and the smallest diameter SWNTs have the largest shifts.

Coating individual single-walled carbon nanotubes with nylon 6,10 through emulsion polymerization.

Solvent microenvironments are formed around individual single-walled carbon nanotubes (SWNTs) by mixing SWNT suspensions with water-immiscible organic solvents. These microenvironments are used to encapsulate the SWNTs with the monomer sebacoyl chloride. Hexamethylene diamine is then injected into the aqueous phase so the formation of nylon 6,10 is restricted to the interface between the microenvironment and water.

Swelling the micelle core surrounding single-walled carbon nanotubes with water-immiscible organic solvents.

Solvatochromic shifts in the absorbance and fluorescence spectra are observed when surfactant-stabilized aqueous single-walled carbon nanotube (SWNT) suspensions are mixed with immiscible organic solvents. When aqueous surfactant-suspended SWNTs are mixed with o-dichlorobenzene, the spectra closely match the peaks for SWNTs dispersed in only pure o-dichlorobenzene. These spectral changes suggest that the hydrophobic region of the micelle surrounding SWNTs swells with the organic solvent when mixed.

Improving the effectiveness of interfacial trapping in removing single-walled carbon nanotube bundles.

Single-walled carbon nanotube (SWNT) bundles are selectively removed from an aqueous dispersion containing individually suspended carbon nanotubes coated with gum Arabic via interfacial trapping. The suspensions are characterized with absorbance, fluorescence, and Raman spectroscopy as well as atomic force microscopy (AFM) and rheology. The resulting aqueous suspensions have better dispersion quality after interfacial trapping and can be further improved by altering the processing conditions.