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Highly Stretchable Carbon Nanotube Fibers with Tunable and Stable Light Emission
摘要： Carbon nanotubes (CNTs) possess intriguing photoluminescence properties, and CNT fibers emit strong incandescent light thus act as macroscopic light sources. So far, straight-shaped CNT fibers are a focus of study and their emission properties are elucidated. Here, the authors show that helical-shaped single-walled carbon nanotube (SWNT) fibers produce uniform and stable incandescent light along the entire fiber under moderate voltages, and the emission intensity is tailored over a wide range by the applied voltage and the elongation of the fiber (up to 70% strain), and in a reversible way during mechanical deformation. Their highly stretchable SWNT fibers with tunable light emission have promising applications in emerging research areas such as wearable electronics and high-performance optoelectronic fiber systems.
关键词： single-wall carbon nanotubes,stretchable device,helical fiber,light emission
更新于2025-09-23 15:22:29
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Direct observation of cross-polarized excitons in aligned single-chirality single-wall carbon nanotubes
摘要： Optical properties of single-wall carbon nanotubes (SWCNTs) for light polarized parallel to the nanotube axis have been studied extensively, whereas their response to light polarized perpendicular to the nanotube axis has not been well explored. Here, by using a macroscopic film of highly aligned single-chirality (6,5) SWCNTs, we performed a systematic polarization-dependent optical absorption spectroscopy study. In addition to the commonly observed angular-momentum-conserving interband absorption of parallel-polarized light, which generates E11 and E22 excitons, we observed a small but unambiguous absorption peak whose intensity is maximum for perpendicular-polarized light. We attribute this feature to the lowest-energy cross-polarized interband absorption processes that change the angular momentum along the nanotube axis by ±1, generating E12 and E21 excitons. Unlike previous observations of cross-polarized excitons in polarization-dependent photoluminescence and circular dichroism spectroscopy experiments, our direct observation using absorption spectroscopy allowed us to quantitatively analyze this resonance. Specifically, we determined the energy and oscillator strength of this resonance to be 1.54 and 0.05, respectively, compared with the values for the E11 exciton peak. These values, in combination with a comparison with theoretical calculations, in turn led to an assessment of the environmental effect on the strength of Coulomb interactions in this aligned single-chirality SWCNT film.
关键词： polarization-dependent,single-wall carbon nanotubes,cross-polarized excitons,aligned film,optical absorption spectroscopy,Coulomb interactions
更新于2025-09-23 15:22:29
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Variance Spectroscopy Studies of Single-Wall Carbon Nanotube Aggregation
摘要： Early stages of single-wall carbon nanotube aggregation in aqueous surfactant suspension have been investigated through combined structure-resolved fluorescence and variance spectroscopies. Following the addition of NaCl to destabilize dispersed samples, variance data revealed strong decreases in the concentrations of emitting particles, while fluorescence spectra showed only modest changes. This indicates the formation of loose aggregates in which electronic contact between individual nanotubes is too limited to perturb their emission. Variance data showed that the initial formation rates of homoaggregates (clusters of the same (n,m) species) increase superlinearly with NaCl concentration. Co-variance analysis gave complementary structure-resolved data on emissive heteroaggregates. For both types of clusters, it is found that the initial aggregation rates correlate with species particle concentrations, but show no clear dependence on nanotube structure. Variance spectroscopy can sensitively detect and characterize small loose clusters of carbon nanotube that are not observable by other spectroscopic methods.
关键词： heteroaggregates,homoaggregates,aggregation,fluorescence spectroscopy,variance spectroscopy,single-wall carbon nanotubes
更新于2025-09-23 15:21:01
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Highly sensitive ultraviolet photodetectors based on single wall carbon nanotube-graphene hybrid films
摘要： An ultraviolet (UV) photodetector was fabricated by depositing single wall carbon nanotubes (SWCNTs) on the surface of a graphene field-effect transistor (GFET) with buried gate electrode structure. A photoresponsivity with a value as high as 204.5 A/W was obtained under a 365-nm LED light illumination with an incident power of 3.9 μW. The photoresponsivity of our photodetector is about four orders higher in magnitude than that of a recently reported UV photodetector, which is based on CNTs/graphene hybrid films with a photoresponsivity of 2.3 × 10?2 A/W. With increasing the source-drain voltage of the SWCNTs modified GFET, the photoresponsivity can be further enhanced. In addition, the photoresponsivity can also be tuned by applying a small gate voltage. This work provides a simple and feasible method to create highly sensitive UV photodetectors based on all-carbon hybrid films, which are important in many applications such as military surveillance, biomedical instrumentation and environmental monitoring.
关键词： Ultraviolet,Graphene field effect transistor,Photodetector,Single wall carbon nanotubes
更新于2025-09-19 17:13:59
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Polarization-dependent pulse dynamics of mode-locked fiber laser with near-zero net dispersion
摘要： We demonstrate novel polarization-dependent pulse dynamics in a fiber laser cavity mode-locked by single-wall carbon nanotubes. By managing the net dispersion and polarization state, we obtain two noise-like pulsing procedures with distinctive polarization characteristics. Ultrafast polarization measurements reveal double pulses are produced by the combined effects of double-scroll chaotic polarization attractors and the polarization mode dispersion of single-mode fiber. The corresponding single-shot spectra provide evidence of coherent energy coupling between pulses during the switching process, due to the polarization hole burning of the active medium. The relative results provide new information for the polarization control of ultrafast lasers.
关键词： polarization-dependent pulse dynamics,single-wall carbon nanotubes,polarization hole burning,near-zero net dispersion,mode-locked fiber laser
更新于2025-09-19 17:13:59
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Preparation of Hybrid Molybdenum Disulfide/Single Wall Carbon Nanotube–n-Type Silicon Solar Cells
摘要： Carbon nanotube/silicon (CNT/Si) heterojunction solar cells represent one new architecture for photovoltaic devices. The addition of MoS2 to the devices is shown to increase the e?ciency of the devices. Two structures are explored. In one case, the single wall carbon nanotubes (SWCNTs) and MoS2 ?akes are mixed to make a hybrid, which is then used to make a ?lm, while in the other case, a two layer system is used with the MoS2 deposited ?rst followed by the SWCNTs. In all cases, the solar cell e?ciency is improved largely due to signi?cant increases in the ?ll factor. The rise in ?ll factor is due to the semiconducting nature of the MoS2, which helps with the separation of charge carriers.
关键词： molybdenum disul?de (MoS2),single wall carbon nanotubes (SWCNTs),thin ?lm,solar cells
更新于2025-09-16 10:30:52
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Global alignment of solution-based single-wall carbon nanotube films via machine-vision controlled filtration
摘要： Over the past decade, substantial progress has been made in the chemical control (chiral enrichment, length sorting, handedness selectivity, and filling substance) of single-wall carbon nanotubes (SWCNTs). Recently, it was shown that large, horizontally-aligned films can be created out of post-processed SWCNT solutions. Here, we use machine-vision automation and parallelization to simultaneously produce globally-aligned SWCNT films using pressure-driven filtration. Feedback control enables filtration to occur with a constant flow rate that not only improves the nematic ordering of the SWCNT films, but also provides the ability to align a wide range of SWCNT types and on a variety of nanoporous membranes using the same filtration parameters. Using polarized optical spectroscopic techniques, we show that under standard implementation, meniscus combing produces a two-dimensional radial SWCNT alignment on one side of the film. After we flatten the meniscus through silanation, spatially-resolved nematicity maps on both sides of the SWCNT film reveal global alignment across the entire structure. From experiments changing ionic strength and membrane charging, we provide evidence that the SWCNT alignment mechanism stems from an interplay of intertube interactions and ordered membrane charging. This work opens up the possibility of creating globally-aligned SWCNT film structures for a new-generation of nanotube electronics and optical control elements.
关键词： Nematic ordering,single-wall carbon nanotubes,directional charging,1D crystals
更新于2025-09-11 14:15:04