Browsing by Author "Maruyama, Shigeo"

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    Carbon Nanotubes and Related Nanomaterials: Critical Advances and Challenges for Synthesis toward Mainstream Commercial Applications
    (American Chemical Society, 2018) Rao, Rahul; Pint, Cary L.; Islam, Ahmad E.; Weatherup, Robert S.; Hofmann, Stephan; Meshot, Eric R.; Wu, Fanqi; Zhou, Chongwu; Dee, Nicholas; Amama, Placidus B.; Carpena-Nuñez, Jennifer; Shi, Wenbo; Plata, Desiree L.; Penev, Evgeni S.; Yakobson, Boris I.; Balbuena, Perla B.; Bichara, Christophe; Futaba, Don N.; Noda, Suguru; Shin, Homin; Kim, Keun Su; Simard, Benoit; Mirri, Francesca; Pasquali, Matteo; Fornasiero, Francesco; Kauppinen, Esko I.; Arnold, Michael; Cola, Baratunde A.; Nikolaev, Pavel; Arepalli, Sivaram; Cheng, Hui-Ming; Zakharov, Dmitri N.; Stach, Eric A.; Zhang, Jin; Wei, Fei; Terrones, Mauricio; Geohegan, David B.; Maruyama, Benji; Maruyama, Shigeo; Li, Yan; Adams, W. Wade; Hart, A. John
    Advances in the synthesis and scalable manufacturing of single-walled carbon nanotubes (SWCNTs) remain critical to realizing many important commercial applications. Here we review recent breakthroughs in the synthesis of SWCNTs and highlight key ongoing research areas and challenges. A few key applications that capitalize on the properties of SWCNTs are also reviewed with respect to the recent synthesis breakthroughs and ways in which synthesis science can enable advances in these applications. While the primary focus of this review is on the science framework of SWCNT growth, we draw connections to mechanisms underlying the synthesis of other 1D and 2D materials such as boron nitride nanotubes and graphene.
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    Molecular Dynamics of Catalyst-Free Edge Elongation of Boron Nitride Nanotubes Coaxially Grown on Single-Walled Carbon Nanotubes
    (American Chemical Society, 2024) Hisama, Kaoru; Bets, Ksenia V.; Gupta, Nitant; Yoshikawa, Ryo; Zheng, Yongjia; Wang, Shuhui; Liu, Ming; Xiang, Rong; Otsuka, Keigo; Chiashi, Shohei; Yakobson, Boris I.; Maruyama, Shigeo
    Recent advances in low-dimensional materials have enabled the synthesis of single-walled carbon nanotubes encapsulated in hexagonal boron nitride (BN) nanotubes (SWCNT@BNNT), creating one-dimensional van der Waals (vdW) heterostructures. However, controlling the quality and crystallinity of BNNT on the surface of SWCNTs using chemical vapor deposition (CVD) remains a challenge. To better understand the growth mechanism of the BNNT in SWCNT@BNNT, we conducted molecular dynamics (MD) simulations using empirical potentials. The simulation results suggest that spontaneous BN nucleation is unlikely to occur on the outer surface of the SWCNT when we assume only vdW interaction between the BN and SWCNT layers. However, we observe the elongation of the BNNT when a short BNNT is provided as a seed nucleus on the SWCNT. This grown BNNT structure, with its sharply cut edges, aligns with experimental observations made using transmission electron microscopy (TEM). Moreover, the edge-reconstruction process favors zigzag B edges, which exhibit low edge energy according to the ReaxFF potential. Our simulation successfully provides insights into the catalyst-free growth process of this one-dimensional vdW heterostructure.
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    Photoluminescence sidebands of carbon nanotubes below the bright singlet excitonic levels
    (The American Physical Society, 2009) Murakami, Yoichi; Lu, Benjamin; Kazaoui, Said; Minami, Nobutsugu; Okubo, Tatsuya; Maruyama, Shigeo
    We performed detailed photoluminescence (PL) spectroscopy studies of three different types of single-walled carbon nanotubes (SWNTs) by using samples that contain essentially only one chiral type of SWNT, (6,5), (7,5), or (10,5). The observed PL spectra unambiguously show the existence of an emission sideband at ∼140 meV below the lowest singlet excitonic (E11) level, whose identity and origin are now under debate. We find that the energy separation between the E11 level and the sideband is independent of the SWNT diameter within our experimental certainty. Based on this, we ascribe the origin of the observed sideband to coupling between K-point phonons and dipole-forbidden dark excitons, as recently suggested based on the measurement of (6,5) SWNTs.