Spectroscopic Properties of Nanotube–Chromophore Hybrids

Abstract

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. The pyrene tethers form a much stronger attachment to nanotubes compared to anthracene or benzene rings, resulting in more than 80% retention of bound chromophores post-processing. Density functional theory (DFT) calculations show that the binding energy of the chromophores to the nanotubes is maximized for chromophores parallel to the nanotube sidewall, even with the use of tethers; optical second harmonic generation measurements show that there is nonetheless a partial radial orientation of the chromophores on the nanotubes. We find weak electronic coupling between the chromophores and the SWNTs, consistent with noncovalent binding. This weak coupling is still sufficient to quench the chromophore fluorescence through a combination of static and dynamic processes. Photoluminescence measurements show a lack of significant energy transfer from the chromophores to isolated semiconducting nanotubes.

Colorimetric and optical discrimination of halides by a simple chemosensor

“…Extensive previous work has shown that the M06L semi-local functional accurately predicts binding energies in both organometallic compounds 44 as well as noncovalent interactions for large systems. 45 Fully unconstrained geometry optimizations were carried out on both the isolated receptor as well as the various molecular-bound complexes. The DFT-optimized geometries of the complexes are shown in Fig.…”

Giant Raman scattering from J-aggregated dyes inside carbon nanotubes for multispectral imaging

“…Both results are consistent with previous work on bulk 6T@SWNTs in solution, although some fluorescence was detected but at shorter excitation wavelengths 8,9 . Other studies on different dyes inside SWNT reported efficient fluorescence quenching by the SWNTs 12,13,15 and this effect seen in weakly bonded chromophore-SWNT complexes was explored recently in the context of light harvesting applications 16,17 .…”

Photobleaching effect in azo-dye containing epoxy resin films: the potentiality of carbon nanotubes as azo-dye dispensers

“…Particularly, the electronic structure of carbon nanotubes and azo-dye chromophores allows them to weakly interact via a non-covalent binding [1,2]. Among the many possible ways of working with carbon nanotubes and azo-dye chromophores, one alternative turns out from the addition of both carbon nanotubes and azo-dye molecules into a polymeric matrix [3,4].…”