Diameter Of Single-walled Carbon Nanotubes Research Articles

Direct Synthesis of Colorful Single-Walled Carbon Nanotube Thin Films.

In floating catalyst chemical vapor deposition (FC-CVD), tuning chirality distribution and obtaining narrow chirality distribution of single-walled carbon nanotubes (SWCNTs) is challenging. Herein, by introducing various amount of CO2 in FC-CVD using CO as a carbon source, we have succeeded in directly synthesizing SWCNT films with tunable chirality distribution as well as tunable colors. In particular, with 0.25 and 0.37 volume percent of CO2, the SWCNT films display green and brown colors, respectively. We ascribed various colors to suitable diameter and narrow chirality distribution of SWCNTs. Additionally, by optimizing reactor temperature, we achieved much narrower (n,m) distribution clustered around (11,9) with extremely narrow diameter range (>98% between 1.2 and 1.5 nm). We propose that CO2 may affect CO disproportionation and nucleation modes of SWCNTs, resulting in SWCNTs’ various diameter ranges. Our work could provide a new route for high-yield and direct synthesis of SWCNTs with narrow chirality distribution and offer potential applications in electronics, such as touch sensors or transistors.

A Comparison Between Reduced and Intentionally Oxidized Metal Catalysts for Growth of Single‐Walled Carbon Nanotubes

In this article, the authors report a detailed comparative study on the growth of single‐walled carbon nanotubes (SWNTs) from monometallic and its oxide (intentionally oxidized) catalysts. The difference and findings are summarized in the following three aspects. 1) High‐quality SWNTs are also grown from intentionally oxidized Co nanoparticles, but the yield of SWNTs significantly decreases, resulting in random network rather than vertically aligned SWNT arrays. 2) The authors clarify from in‐plane transmission electron microscopy that Co oxide nanoparticles grow SWNTs through an in situ reduction process, which means Co oxide becomes metallic Co after the introduction of ethanol; direct growth from an oxide phase is not observed. 3) Compared to the SWNTs grown by pre‐reduced catalysts, SWNTs grown from intentionally oxidized catalysts show narrower diameter distribution and smaller average diameter from Raman spectra. The strategy also shows similar results in the Ni catalysts. The findings are helpful to improve the controllability of SWNT diameter and morphology, as well as the reproducibility and robustness of CVD process.

Diameter-Dependent Optical Absorption and Excitation Energy Transfer from Encapsulated Dye Molecules toward Single-Walled Carbon Nanotubes.

The hollow cores and well-defined diameters of single-walled carbon nanotubes (SWCNTs) allow for creation of one-dimensional hybrid structures by encapsulation of various molecules. Absorption and near-infrared photoluminescence-excitation (PLE) spectroscopy reveal that the absorption spectrum of encapsulated 1,3-bis[4-(dimethylamino)phenyl]-squaraine dye molecules inside SWCNTs is modulated by the SWCNT diameter, as observed through excitation energy transfer (EET) from the encapsulated molecules to the SWCNTs, implying a strongly diameter-dependent stacking of the molecules inside the SWCNTs. Transient absorption spectroscopy, simultaneously probing the encapsulated dyes and the host SWCNTs, demonstrates this EET, which can be used as a route to diameter-dependent photosensitization, to be fast (sub-picosecond). A wide series of SWCNT samples is systematically characterized by absorption, PLE, and resonant Raman scattering (RRS), also identifying the critical diameter for squaraine filling. In addition, we find that SWCNT filling does not limit the selectivity of subsequent separation protocols (including polyfluorene polymers for isolating only semiconducting SWCNTs and aqueous two-phase separation for enrichment of specific SWCNT chiralities). The design of these functional hybrid systems, with tunable dye absorption, fast and efficient EET, and the ability to remove all metallic SWCNTs by subsequent separation, demonstrates potential for implementation in photoconversion devices.

High-performance single-walled carbon nanotube transparent conducting film fabricated by using low feeding rate of ethanol solution.

We report floating catalyst chemical vapour deposition synthesis of single-walled carbon nanotubes (SWCNTs) for high-performance transparent conducting films (TCFs) using low feeding rate of precursor solution. Herein, ethanol acts as carbon source, ferrocene and thiophene as catalyst precursor and growth promoter, respectively. By adopting a low feeding rate of 4 µl min−1, the fabricated TCFs present one of the lowest sheet resistances of ca 78 Ω sq.−1. at 90% transmittance. Optical characterizations demonstrate that the mean diameter of high-quality SWCNTs is up to 2 nm. Additionally, electron microcopy observations provide evidence that the mean length of SWCNT bundles is as long as 28.4 µm while the mean bundle diameter is only 5.3 nm. Moreover, very few CNT loops can be found in the film. Remarkably, the fraction of individual SWCNTs reaches 24.6%. All those morphology data account for the superior optoelectronic performance of our SWCNT TCFs.

Electronic Structure Control of Sub-nanometer 1D SnTe via Nanostructuring within Single-Walled Carbon Nanotubes.

Nanostructuring, e. g., reduction of dimensionality in materials, offers a viable route toward regulation of materials electronic and hence functional properties. Here, we present the extreme case of nanostructuring, exploiting the capillarity of single-walled carbon nanotubes (SWCNTs) for the synthesis of the smallest possible SnTe nanowires with cross sections as thin as a single atom column. We demonstrate that by choosing the appropriate diameter of a template SWCNT, we can manipulate the structure of the quasi-one-dimensional (1D) SnTe to design electronic behavior. From first principles, we predict the structural re-formations that SnTe undergoes in varying encapsulations and confront the prediction with TEM imagery. To further illustrate the control of physical properties by nanostructuring, we study the evolution of transport properties in a homologous series of models of synthesized and isolated SnTe nanowires varying only in morphology and atomic layer thickness. This extreme scaling is predicted to significantly enhance thermoelectric performance of SnTe, offering a prospect for further experimental studies and future applications.

Molecular dynamics study on the configuration and arrangement of doxorubicin in carbon nanotubes

Carbon nanotubes are potential candidates for drug delivery system (DDS) design due to their capacity to internalize and control the release of molecules. In this work, single-walled carbon nanotubes (SWCNTs) are the high-capacity drug carrier under study, and doxorubicin (DOX) is the model drug. Molecular dynamics simulations were performed to investigate the configuration and arrangement of different loading amounts of DOX in SWCNTs. The results show that the orientation and arrangement of DOX molecules can be influenced by drug concentration and by the diameter of the SWCNT. If the diameter of SWCNT is relatively small and there is strong confinement (e.g., in SWCNT (10,10)), DOX molecules prefer to form a single-file helix inside the SWCNT, which suggests that the controlled loading and release of a single drug molecule can be achieved by precise manufacture of SWCNTs with specific diameters, thus overcoming the disadvantage of aggregated DOX structure in solution and reducing chemotherapy dosage.

(Invited) Diameter-Dependent Optical Absorption and Energy Transfer from Encapsulated Dye Molecules to Single Wall Carbon Nanotubes

The hollow core and well-defined diameters of single-walled carbon nanotubes (SWCNTs) allow for creation of unique one-dimensional hybrid structures by encapsulation of various molecules. For instance, we previously demonstrated that in this way dipolar dye molecules can be naturally aligned in an ideal head-to-tail arrangement to create assemblies with a giant total nonlinear optical response.[1] Here, we show that the optical properties of dye molecules encapsulated in SWCNTs can be strongly modulated by the SWCNT diameter, indicating very specific diameter-dependent stacking and interactions of the molecules. The filling is thoroughly characterized by optical absorption, resonant Raman, and two-dimensional infrared photoluminescence excitation (PLE) spectroscopy. Energy transfer probed by PLE spectroscopy shows the absorption spectrum of the dyes to be strongly diameter-dependent, and transient absorption spectroscopy, simultaneously probing the encapsulated dyes and the host SWCNTs, demonstrates sub-picosecond EET from encapsulated molecules to the host SWCNTs. The design of these functional hybrid systems, with tuneable dye absorption, EET depending on the SWCNT diameter and the ability to remove all metallic SWCNTs by subsequent separation, demonstrates potential for implementation in dedicated photo-conversion devices. [1] S. Cambré, J. Campo et al., Nature Nanotechnol. 10, 248 (2015).

Influence of Carbon Nanotube Chirality on Sodium Cholate Adsorption in Aqueous Suspensions

Established chirality separation techniques for single-wall carbon nanotubes (SWNTs) in aqueous suspensions make use of chirality specific adsorption behavior of surfactants on these nano-carbon surfaces. Here, we investigate the adsorption of sodium cholate on SWNTs of different chirality with diameters ranging from 0.7 to 1 nm. Titration studies are performed at different temperatures by measuring photoluminescence emission energies of the diluted SWNT suspensions. The high sensitivity of the exciton to its environment allows to detect small changes in arrangement and concentration of surfactants on the SWNT surface, as recently shown for the (6,5) chirality by Bergler et al. [1]. Here we report on substrate-induced cooperative adsorption regimes for sodium cholate on five different SWNT chiralities. The critical micelle concentrations of the cholate-SWNT micelles exhibit a linear increase with SWNT diameter, while the thermodynamic stability of the cholate-SWNT micelles decreases. These diameter and temperature dependences may play a key role in the separation of SWNT chiralities by density gradient ultracentrifugation and aqueous two phase extraction and thus may help not only to understand the microscopic sorting mechanisms but also to improve empirical preparation protocols. [1] Bergler et al., Langmuir 2016, 32, 9598-9603, DOI: 10.1021/acs.langmuir.6b02759

Designing Single-Wall Carbon Nanotube Forest Growth for Nanofluidic Applications

Ultrafast fluid transport through the core of single-wall carbon nanotube (SWNT) channels promises to advance membrane applications, from efficient water purification and low-cost separation of high-value components, to next-generation protective garments. For the last application, we recently demonstrated cm2-area, vertically-aligned, SWNT-polymer composite membranes that combined both high breathability and protection in a single functional material, thus breaking the typically elusive trade-off between the two.1 As we seek to further enhance the performance of these membranes, we target vertically-aligned SWNT “forest” growth toward: a) minimizing SWNT diameter to maximize protection via size exclusion; b) maximizing SWNT number density to maximize breathability; and c) scaling up SWNT growth area to eventually incorporate into garments. We perform low-pressure chemical vapor deposition (CVD) in an AIXTRON® Black Magic cold-wall furnace, featuring a wafer-scale, local heater stage and gas showerhead. The combination of a low flux of carbon precursors with sub-nm Fe/Mo catalyst films on alumina-coated Si wafers maintains small-diameter SWNTs. High-resolution TEM and X-ray scattering2 confirm that our forests contain >99% SWNTs below 3.5 nm diameter (on wafers up to 4 inches). Consistent with literature reports, 6 at% Mo optimally preserves small, densely packed particles, templating growth of forests with high number densities up to 1.4x1012 cm-2. In an effort to control the forest thickness and uniformity across large substrate areas, we investigate the area-dependent growth kinetics and temporal density decay. Despite exhibiting a growth rate that is initially uniform across the substrate, growth at the center self-terminates first, while edge growth continues at a sublinear rate for tens of minutes. Understanding these varying reaction lifetimes that arise on a single substrate is key to engineering large-area SWNT membranes with highly uniform transport characteristics. To scale SWNT forest production and overcome non-uniformities in wafer-scale growth, we seek to simplify the catalyst film formulation. While wafer-scale growth from Fe films of equal thickness in the absence of Mo is markedly more robust over multiple sequential batches, the SWNT diameter distributions have larger means and tails, which are detrimental to the rejection properties of our membranes. Tuning the Fe thickness down renders smaller SWNTs, but the range of densities grown from these Fe-only films is 0.2-0.6x1012 cm-2, regardless of thicknesses studied (0.35-0.65 nm). This challenge of accessing a parameter space that co-optimizes growth yield of small, monodisperse diameter, high-density SWNT forests highlights a deficiency in conventional catalyst design and suggests a need for improved designs that could unlock a range of SWNT applications. This work is supported by the Defense Threat Reduction Agency (DTRA) D[MS]2 project under Contract No. BA12PHM123 and was performed under the auspices of U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Bui, N.; Meshot, E. R.; Kim, S.; Peña, J.; Gibson, P. W.; Wu, K. J.; Fornasiero, F., Ultrabreathable and Protective Membranes with Sub-5 nm Carbon Nanotube Pores. Advanced Materials 2016, 28 (28), 5871-5877.Meshot, E.; Zwissler, D. W.; Bui, N.; Kuykendall, T. R.; Wang, C.; Hexemer, A.; Wu, K. J. J.; Fornasiero, F. Quantifying the Hierarchical Order in Self-Aligned Carbon Nanotubes from Atomic to Micrometer Scale. ACS Nano 2017, 11 (6), 5405-5416.

Spontaneous and controlled-diameter synthesis of single-walled and few-walled carbon nanotubes

In this study, we explored the spontaneous and controlled-diameter growth of carbon nanotubes. We evaluated the effects of catalyst density, reduction time, and a number of catalyst coating on the substrate (for multi-walled carbon nanotubes) on the diameter of single-walled carbon nanotubes and the number of layers in few-walled carbon nanotubes. Increasing the catalyst density and reduction time increased the diameters of the carbon nanotubes, with the average diameter increasing from 1.05 nm to 1.86 nm for single-walled carbon nanotubes. Finally, we succeeded in synthesizing a significant double-walled carbon nanotube population of 24%.

Chiral vector and metal catalyst-dependent growth kinetics of single-wall carbon nanotubes

Single-wall carbon nanotubes (SWCNTs) are synthesized by the pyrolysis of cobaltocene and nickelocene in the interior of hosting SWCNTs. In situ Raman spectroscopy elucidates growth kinetics of SWCNTs of nine different chiral vectors (8,8), (12,3), (13,1), (9,6), (10,4), (11,2), (11,1), (9,3) and (9,2) that features faster and slower growth rates. The activation energy of the faster growth increases monotonically with the SWCNT diameter, while that of the slower growth doesn't show a clear dependence, and neither of them depends on the chiral angle. At a given temperature the growth rates of the inner tubes are much higher with nickel than those with cobalt. The activation energy of the faster growth is found to be independent of the metal type, whereas that of the slower growth is metal-specific. The information obtained in the present study is elemental for a large-scale and selective synthesis of single-chirality SWCNTs that are demanded for applications.

Structure factors of carbon nanotubes on the thermal conductivity of carbon nanotube/epoxy composites

The structure factors of carbon nanotubes such as the dispersion, morphology and size have effects on the thermal conductivity of carbon nanotube/epoxy composites (kc). However, the behavior how these structure factors affect the kc has still not been fully understood. To seek the answer, three-dimensional computational models containing various dispersion of bending single wall carbon nanotubes (SWCNTs) are developed using the finite element method. A conjecture is proposed based on these models that the dispersion and the number of the overlapping heat-affected zones (OHAZs) of heat conduction networks play an important role on the kc. To prove the conjecture, a feature parameter–a dispersion coefficient is proposed to quantify the dispersion uniformity. The kc is calculated in models with different dispersion coefficients. The results show that the kc increases with the dispersion coefficient. The effects of the morphology and the size of SWCNTs on the kc could also be explained using this conjecture. SWCNTs with a larger length efficiency and diameter are found to be beneficial to a higher kc. Because a larger length efficiency increases the number of OHAZs and a larger diameter SWCNT has a wider heat-affected zone which also increases the number of OHAZs.

Theoretical and experimental models for the synthesis of single-walled carbon nanotubes and their electrochemical properties

A major challenge in the field of selective synthesis of single-walled carbon nanotubes (SWCNTs) via chemical vapor deposition (CVD) method is lack of established theoretical model for direct selection of metal/support catalyst to grow the corresponding SWCNTs. This has limited the application of these materials, especially, in electronics. In this report, we introduced circumferential and axial distortions in the Extended Tight Binding (ETB) equations to generate our model equations which correlated the numerical magnitude of chiral index (n, m) of SWCNTs directly with mass fractions of metal/support catalyst matrix, respectively. Theoretical predictions of our model equations showed acceptable deviations with ETB model, and two Fe2O3/Al2O3 catalysts were prepared according to this model to grow corresponding SWCNTs (10, 7) and (8, 8) via CVD pyrolysis of C6H14/N2 feedstock. High-resolution transmission electron microscopy analysis revealed bundled SWCNTs while analysis of their Raman profiles showed consistency with the radial breathing modes, diameter and energy band gaps of SWCNTs (10, 7) and (8, 8). Electrochemical analysis of the samples suggested potentials as pseudocapacitor electrodes. If fully explored and optimized, this model may complement or augment the existing in-situ epitaxial growth model.

RETRACTED - Growth of single-walled carbon nanotube at a low temperature by alcohol catalytic chemical vapor deposition using Ru catalysts

ABSTRACTGrowth of single-walled carbon nanotube (SWCNT) was achieved by an alcohol catalytic chemical vapor deposition (CVD) mechanism that was conducted in a high vacuum using Ru catalysts. By optimizing the ethanol pressure, SWCNTs can grow in a wide range of temperature between 500 °C and 900 °C. Both the yield and crystalline quality of SWCNTs reached their maxima at 700 °C. Significantly, the SWCNT growth was achieved even at 450 °C, which was much lower than the growth temperatures that were required for SWCNT growth using Ru catalysts previously. Raman measurements exhibited that the diameter distribution of the SWCNTs that were grown at 450 °C was quite narrow and (11, 4) nanotubes were dominant. The observations of transmission electron microscope (TEM) suggested that the size of the Ru particles were larger than the diameter of SWCNT. Such a relation was similar to the relation observed in the growth of SWCNTs using Pt catalysts.

Growth of single-walled carbon nanotube at a low temperature by alcohol catalytic chemical vapor deposition using Ru catalysts

ABSTRACTGrowth of single-walled carbon nanotube (SWCNT) was achieved by an alcohol catalytic chemical vapor deposition (CVD) mechanism that was conducted in a high vacuum using Ru catalysts. By optimizing the ethanol pressure, SWCNTs can grow in a wide range of temperature between 500 °C and 900 °C. Both the yield and crystalline quality of SWCNTs reached their maxima at 700 °C. Significantly, the SWCNT growth was achieved even at 450 °C, which was much lower than the growth temperatures that were required for SWCNT growth using Ru catalysts previously. Raman measurements exhibited that the diameter distribution of the SWCNTs that were grown at 450 °C was quite narrow and (11, 4) nanotubes were dominant. The observations of transmission electron microscope (TEM) suggested that the size of the Ru particles were larger than the diameter of SWCNT. Such a relation was similar to the relation observed in the growth of SWCNTs using Pt catalysts.

Структурные и термоэлектрические свойства оптически прозрачных тонких пленок на основе одностенных углеродных нанотрубок

AbstractThin films have been produced via a spray method from commercially available single-walled carbon nanotubes (SWCNTs). A SWCNT film thickness has ranged from ~10 to ~80 nm. The SWCNT diameter has accepted values of 1.6–1.8 nm. The existence of SWCNTs longer than 10 μm is established. The optimal thickness of a SWCNT thin film is found to be ~15 nm at which the transmittance exceeds 85%. The specific resistance of SWCNT thin films goes from ~1.5 × 10^–3 to ~3 × 10^–3 Ohm cm at room temperature. The pioneering study of the temperature dependences of the Seebeck coefficient and surface resistance is performed for this type of SWCNT. A surface resistance is found to increase with rising temperature. Furthermore, the Seebeck coefficient of SWCNT thin films weakly depends on temperature. Its value for all samples is evaluated to be ~40 μV/K. According to the sign of the Seebeck coefficient, thin films exhibit hole-type conductivity. Moreover, the power factor of a 15-nm thin SWCNT-film decreases with a temperature increase to 140◦C from the value of approximately ~120 to ~60 μW m^–1 K^–2. A further rise in temperature has led to a gain in the power factor.

Chlorinated paraffins wrapping of carbon nanotubes: A theoretical investigation

How nanomaterials interact with pollutants is the central for understanding their environmental behavior and practical application. In this work, molecular dynamics (MD) and density functional theoretical (DFT) methods were used to investigated the influence of carbon chain length, degree of chlorination, chain configuration, and chirality of chlorinated paraffin (CP) and diameter of single-walled carbon nanotubes (SWNTs) on the interaction between CPs and SWNTs. The simulation results demonstrated that CP chain length and chlorination degree played considerably important roles in determining interaction strength between SWNTs and CPs. The interaction energies increased with increasing chain length and chlorination degree. The chirality of SWNT exerted negligible influence on the interaction energy between SWNTs and CPs. On the contrary, interaction energy increased with increasing radius of SWNTs due to the surface curvatures. This result was rationalized by considering the decrease in SWNT curvature with increasing radius, which resulted in plane-like CNT wall. The negligible influence of CP chain configurations was attributed to relative flexibility of CP carbon chains, which can wrap on tubes through conformational changes with low-energy barriers. MD results indicated that CPs could adsorb on SWNT surface rapidly in aqueous environment. Charge transfer and electronic density results indicated that the interaction between CPs and SWNTs was physisorption in nature. This work provides fundamental information regarding SWNTs as sorbents for CPs extraction and adsorptive removal from environmental water system.

Selective synthesis of single walled carbon nanotubes on metal (iron, nickel or cobalt) sulfate-based catalysts

Selective synthesis of single-walled carbon nanotubes (SWCNTs) is highly desirable for various applications. Among the strategies proposed for achieving this, the method involving sulfur-containing compounds is a promising approach showing the conversion of common cobalt/silica catalysts (Co/SiO2) into chirality selective catalysts. However, the possible influence of sulfur-containing compounds in promoting the selectivity of non-cobalt-based metal/silica catalysts has not been studied. Here three metal sulfate based catalysts (MSO4/SiO2, M=Fe, Ni, or Co) were prepared for SWCNT synthesis under the same growth condition. Detailed SWCNT and catalyst characterizations show that well-dispersed Fe oxides and silicates are formed on Fe2(SO4)3/SiO2, favoring the formation of small diameter (6,5) nanotubes. NiSO4/SiO2 contains a portion of NiSO4 together with Ni silicate and relatively large NiO particles, leading to a wider diameter distribution centered around (8,7) nanotubes. CoSO4/SiO2 consists of dominantly well-dispersed CoSO4 and a small amount of Co silicates, showing the good selectivity toward the relatively larger diameter (9,8) nanotubes with an abundance of 40.6% among the semiconducting nanotubes. Sulfur retained on the catalysts influences the selectivity toward relatively larger diameter SWCNTs. Current work highlights the potential of using metal sulfates with varied decomposition temperatures to achieve the selective growth of SWCNTs.

Influence of Single-Walled Carbon Nanotubes on the Performance of Poly(Azomethine-Ether) Composite Materials

ABSTRACTThe present work is aimed to fabricate a new set of composite materials containing conducting poly(azomethine-ether) reinforced with single-walled carbon nanotubes in the form of single-walled carbon nanotube/poly(azomethine-ether)1–5 for excellent enhanced thermal as well as conducting behavior of poly(azomethine-ether). Single-walled carbon nanotubes of variable loading have been embedded into conducting poly(azomethine-ether) using in situ polymerization technique. Before attempting the polymerization, 1,3-thiazole established poly(azomethine-ether) and its conformable monomers have been prepared and their chemical structures have been correlated by spectral analyses. Furthermore, ηinh and Mw values for poly(azomethine-ether) were found 0.89 dL g−1 and 39723.6, respectively. The fabricated single-walled carbon nanotube/poly(azomethine-ether)1–5 composites were specified and characterized by wide-angle X-ray diffraction patterns, Fourier transform infrared spectroscopy, thermal behavior, scanning electron microscopy, and transmission electron microscopy characterization techniques. A perfect indicative response for this composite material was estimated by Fourier transform infrared spectra and X-ray diffraction as well. Both techniques displayed all intensive characteristic peaks regarding single-walled carbon nanotubes and poly(azomethine-ether) in the spectra or diffraction pattern for single-walled carbon nanotube/poly(azomethine-ether)1–5. The role of single-walled carbon nanotubes on the performance of poly(azomethine-ether) was considerably examined. Single-walled carbon nanotube/poly(azomethine-ether)1–5 showed relatively higher thermal stability. Single-walled carbon nanotube/poly(azomethine-ether)1 displayed the lowest final composite degradation temperature value (552°C), whereas single-walled carbon nanotube/poly(azomethine-ether)5 displayed the highest value (621°C). T10 and T25 values showed a gradual temperature increased while single-walled carbon nanotubes increased. Single-walled carbon nanotube/poly(azomethine-ether)1 showed the lowest thermal stability and single-walled carbon nanotube/poly(azomethine-ether)5 showed the highest thermal stability between all fabricated products. Furthermore, transmission electron microscopy images showed a prominent increase in single-walled carbon nanotubes diameters (40–60 nm). The conductivity values were significantly increased while single-walled carbon nanotubes content was increased and reached to the semiconductors. ε′ values were also increased in both single-walled carbon nanotube/poly(azomethine-ether)4,5 which have higher single-walled carbon nanotubes content.

Low-Temperature Single Carbon Nanotube Spectroscopy of sp3 Quantum Defects.

Aiming to unravel the relationship between chemical configuration and electronic structure of sp3 defects of aryl-functionalized (6,5) single-walled carbon nanotubes (SWCNTs), we perform low-temperature single nanotube photoluminescence (PL) spectroscopy studies and correlate our observations with quantum chemistry simulations. We observe sharp emission peaks from individual defect sites that are spread over an extremely broad, 1000-1350 nm, spectral range. Our simulations allow us to attribute this spectral diversity to the occurrence of six chemically and energetically distinct defect states resulting from topological variation in the chemical binding configuration of the monovalent aryl groups. Both PL emission efficiency and spectral line width of the defect states are strongly influenced by the local dielectric environment. Wrapping the SWCNT with a polyfluorene polymer provides the best isolation from the environment and yields the brightest emission with near-resolution limited spectral line width of 270 μeV, as well as spectrally resolved emission wings associated with localized acoustic phonons. Pump-dependent studies further revealed that the defect states are capable of emitting single, sharp, isolated PL peaks over 3 orders of magnitude increase in pump power, a key characteristic of two-level systems and an important prerequisite for single-photon emission with high purity. These findings point to the tremendous potential of sp3 defects in development of room temperature quantum light sources capable of operating at telecommunication wavelengths as the emission of the defect states can readily be extended to this range via use of larger diameter SWCNTs.