Single-walled Carbon Nanotubes Samples Research Articles

High-loading Fe2O3/SWNT composite films for lithium-ion battery applications

Single-walled carbon nanotube (SWNT) films are a potential candidate as porous conductive electrodes for energy conversion and storage; tailoring the loading and distribution of active materials grafted on SWNTs is critical for achieving maximum performance. Here, we show that as-synthesized SWNT samples containing residual Fe catalyst can be directly converted to Fe2O3/SWNT composite films by thermal annealing in air. The mass loading of Fe2O3 nanoparticles is tunable from 63 wt% up to 96 wt%, depending on the annealing temperature (from 450 °C to 600 °C), while maintaining the porous network structure. Interconnected SWNT networks containing high-loading active oxides lead to synergistic effect as an anode material for lithium ion batteries. The performance is improved consistently with increasing Fe2O3 loading. As a result, our Fe2O3/SWNT composite films exhibit a high reversible capacity (1007.1 mA h g−1 at a current density of 200 mA g−1), excellent rate capability (384.9 mA h g−1 at 5 A g−1) and stable cycling performance with the discharge capacity up to 567.1 mA h g−1 after 600 cycles at 2 A g−1. The high-loading Fe2O3/SWNT composite films have potential applications as nanostructured electrodes for various energy devices such as supercapacitors and Li-ion batteries.

(Invited) Diameter-Dependent Thermal Defunctionalization of Single-Walled Carbon Nanotubes

Covalent sidewall functionalization of single-walled carbon nanotubes (SWCNTs) is an important tool for tailoring their properties for research purposes and applications. In this study, SWCNT samples were first functionalized by reductive alkylation using metallic lithium and 1-iodododecane in liquid ammonia. Samples of the alkyl-functionalized SWCNTs were then pyrolyzed under an inert atmosphere at selected temperatures between 100 and 500 °C to remove the addends. The extent of defunctionalization was assessed using a combination of thermogravimetric analysis, Raman measurements of the RBM, D, and G bands, absorption spectroscopy of the first- and second-order van Hove peaks, and near-IR fluorescence spectroscopy of (n,m)-specific emission bands. These measurements all indicate a substantial dependence of defunctionalization rate on nanotube diameter, with larger diameter nanotubes showing more facile loss of addends. The effective activation energy for defunctionalization is estimated to be a factor of ~1.44 greater for 0.76 nm diameter nanotubes as compared to those with 1.24 nm diameter. The experimental findings also reveal the quantitative variation with functionalization density of the Raman D/G intensity ratio and the relative near-IR fluorescence intensity. Pyrolyzed samples show spectroscopic properties that are equivalent to those of SWCNTs prior to functionalization. The strong structure-dependence of defunctionalization rate suggests a new approach for diameter-sorting of mixed SWCNT samples on relatively large scales without ultrasonic agitation. In addition, properties of a new reactor designed for large-scale functionalization of SWCNTS will be presented. Figure 1

Variance Spectroscopy Monitors the Sonication-Induced Cutting and Debundling of Single-Walled Carbon Nanotubes

It is well known that ultrasonic processing is a crucial step for preparing suspensions of individualized single-walled carbon nanotubes (SWCNTs). Sonication disaggregates nanotube bundles but can also cut long nanotubes into shorter segments and introduce defect sites that degrade optical properties. To study these processes in detail, we have applied the newly developed method of variance spectroscopy.1 In this technique, we analyze fluorescence spectra from many different small regions of a dilute SWCNT sample to determine the variations in emission brought about by statistical changes in composition. By analyzing the first and second moments of the intensity distributions at each wavelength, we construct the mean and variance spectra. Simple analysis of these spectra then reveals the number of particles per unit volume of different (n,m) species present within the mixed sample and the average emission per particle for various (n,m) species. Deeper data analysis gives covariance plots, showing aggregation between different species, and third moment (skew) spectra, showing aggregation of individual species. Starting with a sample of relatively long SWCNTs that had been dispersed in surfactant solution by high shear mixing, we measured variance spectra as a function of sonication time and power. We found that the number density values for every (n,m) species increased with sonication time, reflecting initial further disaggregation and a slower cutting process. These rates of number density increase showed no apparent dependence on nanotube diameter or chiral angle. To confirm the changes in SWCNT length caused by cutting, we also measured full length distributions using the diffusion-based LAND method.2 Findings from these length distributions were compared to the change in number density values in order to disentangle the effects of debundling and cutting. We believe that this is the first study to separately observe these effects. Damage to SWCNTs during continued sonication was monitored through decreases in the values of emission per particle, as determined from variance spectra. We also introduce here the use of skew analysis to obtain a quantitative index of self-aggregation. The experimental results will be compared to findings from a numerical model constructed to represent the main processes occurring during sonication. Our study should allow the optimized preparation of SWCNT dispersions. 1. J. K. Streit, S. M. Bachilo, S. R. Sanchez, C.-W. Lin, and R. B. Weisman, J. Phys. Chem. Lett., 3976-3981 (2015). 2. J. K. Streit, S. M. Bachilo, A. V. Naumov, C. Khripin, M. Zheng, and R. B. Weisman, ACS Nano, 6 (9), 8424-8431 (2012).

Removal of sodium dodecyl sulfate surfactant from aqueous dispersions of single-wall carbon nanotubes

A reagent-based treatment method was developed for the removal of sodium dodecyl sulfate (SDS) from aqueous dispersions of single-wall carbon nanotubes (SWCNTs). Based on a survey of various reagents, organic solvents emerged as the most effective at interrupting the SDS:SWCNT interaction without producing deleterious side reactions or causing precipitation of the surfactant. Specifically, treatment with acetone or acetonitrile allows for the facile isolation of SWCNTs with near complete removal of SDS through vacuum filtration, resulting in a 100x reduction in processing time. These findings were validated via quantitative analysis using thermogravimetric analysis, Raman spectroscopy, 4-point probe electrical measurement, and X-ray photoelectron spectroscopy. Subsequent thermal oxidation further enhances the purity of the reagent treated samples and yields bulk SWCNT samples with >95% carbonaceous purity. The proposed reagent treatment method thus demonstrates potential for large volume SWCNT processing.

Chirality-Controlled Synthesis and Applications of Single-Wall Carbon Nanotubes

Preparation of chirality-defined single-wall carbon nanotubes (SWCNTs) is the top challenge in the nanotube field. In recent years, great progress has been made toward preparing single-chirality SWCNTs through both direct controlled synthesis and postsynthesis separation approaches. Accordingly, the uses of single-chirality-dominated SWCNTs for various applications have emerged as a new front in nanotube research. In this Review, we review recent progress made in the chirality-controlled synthesis of SWCNTs, including metal-catalyst-free SWCNT cloning by vapor-phase epitaxy elongation of purified single-chirality nanotube seeds, chirality-specific growth of SWCNTs on bimetallic solid alloy catalysts, chirality-controlled synthesis of SWCNTs using bottom-up synthetic strategy from carbonaceous molecular end-cap precursors, etc. Recent major progresses in postsynthesis separation of single-chirality SWCNT species, as well as methods for chirality characterization of SWCNTs, are also highlighted. Moreover, we discuss some examples where single-chirality SWCNTs have shown clear advantages over SWCNTs with broad chirality distributions. We hope this review could inspire more research on the chirality-controlled preparation of SWCNTs and equally important inspire the use of single-chirality SWCNT samples for more fundamental studies and practical applications.

Assessing Inhomogeneity in Sorted Samples of Single-Walled Carbon Nanotubes through Fluorescence and Variance Spectroscopy

Detailed spectroscopic analysis has been used to study the homogeneity of single-walled carbon nanotube fractions carefully prepared by nonlinear density gradient ultracentrifugation sorting. Two distinct colored bands containing (6,5) enantiomers were subdivided into several extracted fractions that were separately diluted with sodium cholate surfactant and characterized by fluorescence, absorption, and variance spectroscopy. Values were measured for emission and absorption peak positions, Stokes shifts, emission peak widths, and emissive quantum yields. In addition, variance data were used to find relative emission per nanotube and to plot covariance slices representing homogeneous emission spectra. It was found that emission from SWCNTs within the upper enantiomer band shifts to shorter wavelengths with increasing depth in the centrifuge tube. In the lower enantiomer band such spectral shifts were not observed, but the emissive quantum yields decreased with depth. Variance analysis revealed spectral differences among SWCNTs within the same fraction of the same band. It is concluded that current methods for density gradient ultracentrifugation sorting produce samples that retain measurable structural and spectral inhomogeneities.

Lower limits of detection in using carbon nanotubes as thermoluminescent dosimeters of beta radiation

World-wide, on-going intensive research is being seen in adaptation of carbon nanotubes (CNTs) for a wide variety of applications, particular interest herein being in the thermoluminescent (TL) properties of CNTs and their sensitivity towards energetic radiations. Using beta radiation delivering dose levels of a few Gy it has been observed in previous study that strain and impurity defects in CNTs give rise to significant TL yields, providing an initial measure of the extent to which electron trapping centres exist in various qualities of CNT, from super-pure to raw. This in turn points to the possibility that there may be considerable advantage in using such media for radiation dosimetry applications, including for in vivo dosimetry. CNTs also have an effective atomic number similar to that of adipose tissue, making them suitable for soft tissue dosimetry. In present investigations various single-wall carbon nanotubes (SWCNT) samples in the form of buckypaper have been irradiated to doses in the range 35–1.3Gy, use being made of a 90Sr beta source, the response of the CNTs buckypaper with dose showing a trend towards linearity. It is shown for present production methodology for buckypaper samples that the raw SWCNT buckypaper offer the greatest sensitivity, detecting doses down to some few tens of mGy.

Preparation of Horizontal Single-Walled Carbon Nanotubes Arrays.

The synthesis of SWNTs has achieved great success with the development of synthetic methodologies. From the viewpoint of exploiting the exceptional electrical properties of single-walled carbon nanotubes (SWNTs) in advanced applications, one of the most difficult challenges is how to assemble the SWNTs with high degrees of alignment and purity in electronic conducting (mainly semiconducting) behavior into functional nanodevices. Numerous approaches have been developed to reach this goal, which could be divided into two categories. One is direct preparation of SWNT arrays on the substrate, and the other is self-assembly of pre-sorted SWNTs from solution. The former one obtains SWNT arrays via chemical vapor deposition (CVD) growth, with the sorting realized by either selective growth or post-growth treatment; the latter one assembles SWNT into arrays from solution, with the sorting process occurring before the aligning process in most cases. This review will highlight both in situ and post-synthetic approaches for preparing samples of aligned arrays of SWNTs with well-defined electronic properties-including the working mechanism for directional growth of SWNTs, growth/sorting methods like catalyst engineering, cloning/cap engineering, in situ etching, and ex situ selective removal/etching for surface-grown SWNT sample, and assembling technologies from SWNT solution such as dielectrophoresis, adsorption on lithographically patterned and/or chemically functionalized substrates, Langmuir-Blodgett and Langmuir-Schaefer techniques, and evaporation-driven self-assembly-and research efforts towards direct growth of arrays of complex SWNT structures.

Elemental Quantification and Residues Characterization of Wet Digested Certified and Commercial Carbon Materials.

Inductively coupled plasma optical emission spectroscopy (ICP-OES) is a common, relatively low cost, and straightforward analytical technique for the study of trace quantities of metals in solid materials, but its applicability to nanocarbons (e.g., graphene and nanotubes) has suffered from the lack of efficient digestion steps and certified reference materials (CRM). Here, various commercial and certified graphitic carbon materials were subjected to a "two-step" microwave-assisted acid digestion procedure, and the concentrations of up to 18 elements were analyzed by ICP-OES. With one exception (Sm), successful quantification of all certified elements in the two reference nanocarbons studied was achieved, hence validating the sample preparation approach used. The applicability of our "two-step" protocol was further confirmed for a commercial single-walled carbon nanotube sample. However, the digestion was markedly incomplete for all other commercial materials tested. Where possible, the digestion residues of the carbon materials analyzed (CRM included) were characterized to understand the structural changes that take place and how this may explain the challenge of disintegrating graphitic carbon. In this respect, it was found that solid state nuclear magnetic resonance holds considerable promise as a nonlocalized, easily interpretable, and reliable tool to access the efficient disintegration of these materials.

Optical properties of single-walled carbon nanotubes highly separated in semiconducting and metallic tubes functionalized with poly(vinylidene fluoride)

In this paper, the interaction of poly(vinylidene fluoride) (PVDF) with single-walled carbon nanotubes (SWNTs) highly separated in metallic (M) and semiconducting (S) tubes is studied by resonant Raman scattering and FTIR spectroscopy. In this order, the PVDF/SWNTs membranes were prepared by the evaporation of dimethylformamide (DMF) from PVDF solutions containing i) the as-prepared SWNTs samples, i.e., as mixtures of metallic (33%) and semiconducting (66%) tubes (M + S-SWNTs), ii) SWNTs highly separated in metallic tubes (98%, M-SWNTs), and iii) SWNTs highly separated in semiconducting tubes (99%, S-SWNTs). An increase in the PVDF β phase weight, highlighted by the increase in the absorbance of IR band at 843 cm−1, is reported to take place in the presence of M + S-SWNTs and S-SWNTs. An increase of the PVDF γ crystalline phase weight is reported for the PVDF/M + S-SWNTs, PVDF/M-SWNTs and PVDF/S-SWNTs membranes. Using Raman scattering, a donor-acceptor interaction is invoked to take place at the interface PVDF/M + S-SWNTs and PVDF/S-SWNTs. In the case of the membranes based on PVDF and M-SWNTs, the changes reported in Raman spectra of the two constituents are explained on the base induction-interaction forces between the permanent dipole of PVDF and induced dipole of M-SWNTs.

Low-Temperature Phase Transformation Accompanied with Charge-Transfer Reaction of Polyiodide Ions Encapsulated in Single-Walled Carbon Nanotubes

In order to understand the reason why polyiodide ions encapsulated in single-walled carbon nanotubes (SWCNTs) drastically improve the electric conductivity and the water dispersibility of SWCNTs at low temperature, we performed in situ Raman measurements of polyiodide ions encapsulated in three kinds of SWCNTs having different mean tube diameters under low temperature down to −100 °C. It was found that, for all the three samples, the Raman peak intensities of polyiodide ions increase and the G-band peak position of SWCNTs shifts toward the higher-wavenumber side with decreasing temperature. It means that the charge-transfer from SWCNTs to encapsulated iodine molecules increases with decreasing temperature and that hole-doping level of SWCNTs increases at low temperature. Furthermore, the peak profiles changed with temperature drastically for polyiodide ions encapsulated in the SWCNT sample having the largest mean tube diameter of 2.5 nm. This change indicates the structural transformation of polyiodide ions in SWCNTs. These experimental results can be explained by the promotion of the chain-like polyiodide ion formation at low temperature. It was discussed with the control experiment using amylose that the promotion of the polyiodide ion formation at low temperature is characteristic for iodine molecules encapsulated in SWCNTs.

Disentangling Vacancy Oxidation on Metallicity-Sorted Carbon Nanotubes

Pristine single-walled carbon nanotubes (SWCNTs) are rather inert to O2 and N2, which for low doses chemisorb only on defect sites or vacancies of the SWCNTs at the ppm level. However, very low doping has a major effect on the electronic properties and conductivity of the SWCNTs. Already at low O2 doses (80 L), the X-ray photoelectron spectroscopy (XPS) O 1s signal becomes saturated, indicating nearly all of the SWCNT’s vacancies have been oxidized. As a result, probing vacancy oxidation on SWCNTs via XPS yields spectra with rather low signal-to-noise ratios, even for metallicity-sorted SWCNTs. We show that, even under these conditions, the first-principles density functional theory calculated Kohn–Sham O 1s binding energies may be used to assign the XPS O 1s spectra for oxidized vacancies on SWCNTs into its individual components. This allows one to determine the specific functional groups or bonding environments measured. We find the XPS O 1s signal is mostly due to three O-containing functional groups on SWCNT vacancies: epoxy (C2>O), carbonyl (C2>C═O), and ketene (C═C═O), as ordered by abundance. Upon oxidation of nearly all of the SWCNT’s vacancies, the central peak’s intensity for the metallic SWCNT sample is 60% greater than that for the semiconducting SWCNT sample. This suggests a greater abundance of O-containing defect structures on the metallic SWCNT sample. For both metallic and semiconducting SWCNTs, we find O2 does not contribute to the measured XPS O 1s spectra.

Preparation of tritium-labeled modified single-walled carbon nanotubes for pharmacokinetic studies

Tritium was introduced by the thermal activation method into samples of single-walled carbon nanotubes modified with diaminotriethylene glycol. Chemical linking of the modifier considerably increased the specific radioactivity of the product. The maximal specific radioactivity was reached when “hot” (2000 K) tritium atoms acted on targets of modified nanotubes kept at 295 K. The main pharmacokinetic parameters of tritium-labeled modified carbon nanotubes upon intravenous administration into mongrel rats chosen as a model were determined.

Advanced Spectral Analysis for Characterizing Single-Walled Carbon Nanotube Samples

Single-walled carbon nanotubes (SWCNTs) are a family of 1D nanomaterials with the potential for a range for novel applications. However, accurate and convenient characterization is still an important challenge, since most SWCNT samples contain mixtures of many structural forms ((n,m) species) with different electronic, optical, mechanical, and chemical properties. Fluorescence emission, fluorescence excitation, and absorption spectra of such mixed samples are complex superpositions, with each (n,m) species giving multiple peaks. Therefore proper sample analysis requires detailed knowledge of the positions, widths, and intensities of those spectral features. Here we report progress in determining semiconducting SWCNT sample compositions by carefully analyzing the absorption and emission spectra simultaneously. One step in this approach is determining detailed fluorescence excitation spectra. For this we have prepared samples enriched in a single (n,m) and carefully measured their excitation spectra. Each such spectrum was broken down and modeled as features representing SWCNT electronic and vibronic transitions. We then deduced Voigt or Pearson line shapes that represent positions, widths, and intensities of these peaks as a function of nanotube structure. This has allowed us to construct a model for fluorescence excitation spectra that can be applied to (n,m) species beyond those that were directly measured. Similarly, to represent (n,m)-dependent emission spectra, we have made careful bulk and single-nanotube studies of features from the singlet bright exciton (E11) and three secondary emissive sidebands. We deduced parameters describing these features as a function of nanotube structure to construct a robust model for SWCNT emission spectra. This model, when combined with the one for excitation, allows the fluorescence spectra of nanotube mixtures to be properly analyzed as a sum of contributions from multiple (n,m) species. Although this procedure does not reveal absolute species concentrations, the fluorescence analysis can be combined with absorption analysis and recent data for SWCNT absolute absorption cross sections to obtain quantitative sample compositions. For this purpose, the absorption spectrum of a mixed sample is simulated as a background function plus components determined from the fluorescence emission and excitation profiles for the (n,m) species that were found to be present. Then the separate E11 (n,m) absorbance components are divided by their structure-specific absorption cross sections to find absolute species concentrations.

(Invited) Aligning Organic Dipolar Molecules in Carbon Nanotubes for Nonlinear Optics

The 1D character of single-walled carbon nanotubes (SWCNT) combined with their mechanical robustness, chemical inertness and wide range of diameters makes them ideal nanocontainers for various molecules. Here we show that by encapsulating elongated dipolar molecules in the 1D internal channel of SWCNTs, Coulomb interactions naturally favour a polar head-to-tail alignment of the molecular dipoles, resulting in a cooperative enhancement of directional properties, such as the dipole moment and the second-order nonlinear optical (NLO) response.[1] This principle is demonstrated for a prototypical dipolar molecule encapsulated in various SWCNT samples. The encapsulation is evidenced by extensive wavelength-dependent fluorescence-excitation and resonant Raman experiments on bile-salt solubilised dye-filled SWCNTs[2], revealing the effect of encapsulation on the vibrational and electronic properties of the SWCNTs and the encapsulated molecules.[3-6] The polar alignment is demonstrated by wavelength-dependent hyper Rayleigh scattering experiments (HRS)[7-9] (i.e. second harmonic light scattering). The newly synthesized organic nanohybrids possess a giant total dipole moment and NLO response, corresponding to ~70 identically aligned molecules (HRS intensity scaling quadratically with this number). These nanohybrids form solution processible building blocks highly interesting for the development of electro-optic modulators and switches.

(Invited) Spectral Triangulation: A Novel 3D Method for Locating Single-Walled Carbon Nanotubes In Vivo

Nanomaterials with luminescence in the short-wave infrared (SWIR) region are of special interest for biological research and medical diagnostics because of relatively favorable tissue transparency in that region. Single-walled carbon nanotubes (SWCNTs) show sharp SWIR spectral signatures and therefore have the potential for noninvasive detection and imaging of cancerous tumors when linked to selective targeting agents such as antibodies. However, such applications face the challenge of detecting and localizing the source of light emission from inside tissues. We present here a new method, called spectral triangulation, for sensitively locating SWCNT emission sources in three dimensions using only optical measurements at the specimen surface. SWCNTs inside tissue phantoms are excited by an LED array, and resulting SWIR emission is captured by a scanning fiber optic probe coupled to an InGaAs spectrometer or avalanche photodiode detector. Because of water absorption, attenuation of the SWCNT fluorescence in tissues is strongly wavelength-dependent. We can therefore gauge the distance between SWCNTs and probe by analyzing differential changes in the measured SWCNT emission spectra. SWCNT fluorescence is clearly detected though as much as 22.5 mm of tissue phantom, and the three-dimensional locations of SWCNT samples are deduced with sub-millimeter accuracy at depths up to 10 mm. Our method can also distinguish and locate dual SWCNT sources within tissues.

Influence of Single-Walled Carbon Nanotubes Enriched in Semiconducting and Metallic Tubes on the Vibrational and Photoluminescence Properties of Poly(para-phenylenevinylene)

A new synthesis method based on the electrochemical reduction of α,α,α′,α′-tetrabromo-p-xylene in the presence of single-walled carbon nanotubes (SWNTs) is used to obtain composites of carbon nanotubes (CNTs) functionalized with poly(para-phenylenevinylene) (PPV). To separate the effects of metallic and semiconducting CNTs on their interaction with PPV, the experiments are carried out with SWNTs enriched in semiconducting (S, 99%) and metallic (M, 98%) tubes. Significant changes in the relative intensity and shift of the radial breathing vibrational mode are reported in the Raman spectra of the as-prepared SWNTs samples, i.e., as mixtures of metallic (33%) and semiconducting (66%) entities and SWNTs enriched in M tubes (98%) that result from the electrofunctionalization with PPV. This different behavior originates in the noncovalent and covalent functionalization of SWNTs enriched in M and S SWNTs tubes with PPV, respectively. A gradual decrease in the absorption of the infrared (IR) bands of PPV situated...

Ultrafast Energy Transfer from Fluorene Polymers to Single-Walled Carbon Nanotubes in Wrapped Carbon Nanotube Bundles

Conjugated polymers can selectively wrap around single-walled carbon nanotubes (SWNTs) with specific chiral angles and diameters. Such a hybrid material containing both SWNTs and polymers is attractive for applications such as organic photovoltaic devices and photosensors. In this study, we investigate excitation energy transfer (EET) in a paper form of semiconducting SWNTs wrapped by poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) by means of photoluminescence (PL) excitation spectroscopy and time-resolved luminescence spectroscopy. Photoluminescence excitation maps and spectra show PL peaks when the 0–0 singlet transition of PFO is excited at 2.88 eV, as well as peaks corresponding to EET between semiconducting SWNTs wrapped by PFO. The PL decay time measured for a drop-cast PFO film is 82 ps, whereas the decay time due to PFO in the PFO-wrapped SWNT sample is as short as 0.38 ps. From these results, the EET rate between PFO and SWNTs is estimated to be 2.6 × 1012 s–1. Comparison of the highest occupied molec...

Theoretical investigation of the solubilization of COOH-functionalized single wall carbon nanotubes in water

The paper discusses the impact of functionalization in understanding the solubility of (n, 0) single walled carbon nanotube (SWCNT) with varying diameters (n=8–16) to increase its dispersion in water with the aide of spin-unrestricted density functional theory (DFT). A finite nanotube model saturated with hydrogen at both ends was functionalized with a carboxylic acid at the sidewall. Functionalization resulted in an enhancement in the solubility of the nanotubes in water which can be explained by the increase in dipole moment as visualized in the HOMO–LUMO surface plots. This behavior depends on the tube diameter marked with saw tooth like periodic features which originated from their different π bonding structures manifested in the electronic band gaps. Furthermore, as the degree of sidewall functionalization increases, the SWCNT sample becomes more soluble as assessed by the calculated Gibbs free energies of solvation.

Photoinduced Absorption within Single-Walled Carbon Nanotube Systems

We study the photoabsorption properties of photoactive bulk polymer/fullerene/nanotube heterojunctions in the near-infrared region. By combining pump–probe spectroscopy and linear response time-dependent density functional theory within the random phase approximation (TDDFT-RPA) we elucidate the excited state dynamics of the E11 transition within (6,5) and (7,5) single-walled carbon nanotubes (SWNTs) and combined with poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) in P3HT/PCBM/SWNT blended samples. We find the presence of a photoinduced absorption (PA) peak is related mainly to the width of the photobleach (PB) peak and the charge carrier density of the SWNT system. For mixed SWNT samples, the PB peak is too broad to observe the PA peak, whereas within P3HT/PCBM/SWNT blended samples P3HT acts as a hole acceptor, narrowing the PB peak by exciton delocalization, which reveals a PA peak. Our results suggest that the PA peak originates from a widening of the band gap in the presence of excited electrons and holes. These results have important implications for the development of new organic photovoltaic heterojunctions including SWNTs.