Bundling of single-walled carbon nanotubes (SWCNTs) significantly undermines their superior thermal and electrical properties. Realizing stable, homogeneous, and surfactant-free dispersion of SWCNTs in solvents and composites has long been regarded as a key challenge. Here, we report amine-containing aromatic and cyclohexane molecules, which are common chain extenders (CEs) for epoxy curing in industry, can be used to effectively disperse CNTs. We achieve single-tube-level dispersion of SWCNTs in CE solvents, as demonstrated by the strong chirality-dependent absorption and photoluminescence emission. The SWCNT-CE dispersion remains stable under ambient conditions for months. The excellent dispersibility and stability are attributed to the formation of an n-type charge-transfer complex through the NH−π interaction between the amine group of CEs and the delocalized π bond of SWCNTs, which is confirmed by the negative Seebeck coefficient of the CE-functionalized SWCNT films, the red shift of the G band in the Raman spectra, and the NH−π peak in X-ray photoelectron spectroscopy. The high dispersibility of CEs significantly improves the electrical and thermal transport of macroscale CNT assemblies. The sheet resistance of the CE-dispersed SWCNT thin films reaches 161 Ω sq–1 at 80.8% optical transmittance after functional modification by HNO3. Moreover, the CEs cross-link CNTs and epoxy molecules, forming a pathway for phonon transport in CNT/epoxy nanocomposites. The thermal conductivity of the CE–CNT–epoxy composite is enhanced by 1850% compared with the original epoxy, which is the highest enhancement reported to date for CNT/epoxy nanocomposites. The CE-based NH−π interaction provides a new paradigm for the effective and stable dispersion of SWCNTs in a facile and scalable process.
Development of a refractory selective solar absorber (RSSA) is the key to unlock high-temperature solar thermal and thermochemical conversion. The fundamental challenge of RSSA is the lack of design and fabrication guidelines to simultaneously achieve omnidirectional, broadband solar absorption and sharp spectral selectivity at the desired cutoff wavelength. Here, we realize a ruthenium–carbon nanotube (Ru-CNT) nanocomposite RSSA with multiscale nanoparticle-on-nanocavity plasmonic modes. Ru conformally coated on the sidewalls of CNTs enables a spoof surface plasmon polariton mode for spectra selectivity; Ru nanoparticles formed at the tips of CNTs enable a localized surface plasmon resonance mode and plasmon hybridization for omnidirectional broadband solar absorption. The fabricated Ru-CNT RSSA has a total solar absorption (TSA) of 96.1% with sharp spectral cutoff at 2.21 μm. The TSA is maintained at over 90% for an incident angle of 56°. Our findings therefore guide full-spectrum optical and thermal control from visible to the far-infrared.
Broadband, omnidirectional light absorption in the infrared range is critical for emerging aerospace and ground applications, such as machine vision, autonomous vehicle technology, and aerospace telescope. Broadband absorbers (BBAs) need to possess strong absorption through thin structures for high signal-to-noise ratios, as well as manufacturing scalability and service reliability in harsh environment for practical applications. Such requirements rule out many known absorbing materials such as carbon nanotubes that are intrinsically lossy and fragile. Achieving strong lightmatter interaction in the mid-and long-wavelength infrared ranges has been extremely challenging despite long-standing research efforts. Here, an aerospace-grade, ≈2.0 µm-thick hierarchical coral-structured titanium nitride (coral-TiN) plasmonic metamaterial is experimentally realized with over 90% omnidirectional absorption across the visible to the long-wavelength infrared range (0.25-25 µm) using a scalable fabrication method. The broadband optical control of the coral-TiN BBA is achieved by the superposition of the hybridized plasmonic mode in the visible and near-infrared, the cavity mode in the short-wavelength infrared as well as the propagating surface plasmon polariton mode in the mid-and long-wavelength infrared. With conformal alumina coating, the plasmonic absorber demonstrates outstanding reliability in rigorous aerospace-grade tests under harsh mechanical and thermal environmental conditions.
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