Photoluminescence (PL) brightening is clearly observed through the direct morphology transition from isolated to thin bundled vertically- and individually freestanding single-walled carbon nanotubes (SWNTs). On the basis of the precise spectra analysis and equation-based estimation of the PL time trace, the origin of the PL brightening is consistently explained in terms of the exciton energy transfer through the tube bundles. The PL brightening is also revealed to obviously depend on SWNT diameters. Only the small-diameter rich sample can realize the PL brightening, which can be explained by the different concentrations of metallic SWNTs causing a PL quenching. Since it can be possible to fabricate brightly illuminating nanotubes on various kinds of substrates, the bundle engineering with freestanding nanotubes is expected to be a potential candidate for realizing the nanotube-based PL device fabrication.
"This interaction is one of the most elusive effects in carbon nanotubes photophysics, in that the investigation of these effects is strongly limited by the quality and control of the nanotubes separation . Up to now, very few studies on energy transfer in SWCNT aggregates based on steadystate measurements such as high-resolution optical microscopy and photoluminescence excitation spectroscopy have been reported      . It is known, however, that precise information of the energy transfer can be obtained only with time-resolved spectroscopy . "
[Show abstract][Hide abstract] ABSTRACT: Semiconducting single-walled carbon nanotubes (SWCNTs) sorted by conjugated polymers are of great interest for electronic and optoelectronic applications. Here we demonstrate by optical methods that the selectivity of conjugated polymers for semiconducting SWCNTs is influenced by the structure of their side-chains and/or the molecular weight of the macromolecules, and that side chain functionalities determine the solubility in different dispersion media. Moreover, high resolution time-resolved photoluminescence measurements provide evidence of energy transfer from tubes with larger band gaps compared to those with smaller band gaps coexisting in SWCNT bundles.
", excitonic energy transfer (EET)   , or bright phonon sidebands (BSs) of dark K-momentum excitons . EET occurs in bundles when the excitation of the eh ii of large bandgap donor SWNTs (d-SWNT) induces emission from the eh 11 of a smaller bandgap acceptor (a- SWNT)  . "
[Show abstract][Hide abstract] ABSTRACT: We present an overview of the recent developments in de-bundling and sorting of Single-Wall Carbon Nanotubes (SWNTs), which are useful for hi-tech applications in dye sensitized solar cells (DSSCs). Applications of SWNTs as transparent and conductive films, catalyst, and scaffold in DSSCs are also reviewed.
International Journal of Photoenergy 01/2010; 2010. DOI:10.1155/2010/727134 · 1.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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. The solvatochromic shifts of the aqueous SWNT suspensions are reversible once the solvent evaporates. However, some surfactant-solvent systems show permanent changes to the fluorescence emission intensity after exposure to the organic solvent. The intensity of some large diameter SWNT (n, m) types increase by more than 175%. These differences are attributed to surfactant reorganization, which can improve nanotube coverage, resulting in decreased exposure to quenching mechanisms from the aqueous phase.
Journal of the American Chemical Society 12/2008; 130(48):16330-7. DOI:10.1021/ja806586v · 12.11 Impact Factor
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