Cloaking by π‐electrons in the infrared

Pekker, Áron; Németh, Gergely; Botos, Ákos; Tóháti, Hajnalka M.; Borondics, Ferenc; Osváth, Z.; Biró, László Péter; Walker, Kate E.; Khlobystov, Andrei N.

doi:10.1002/pssb.201600399

Cited by 3 publications

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“…To further probe the efficiency of encapsulation of C 60 in BNNTs, IR and UV–vis spectroscopy were performed ( Figure ). Being electrically insulating and optically transparent, BNNTs should allow the vibrations of guest molecules to be directly analyzed by IR spectroscopy, unlike CNTs that have often hindered such analysis . Indeed, the IR spectrum of toluene‐washed C 60 @BNNT (Figure a) contains prominent bands at 803 and 1375 cm −1 corresponding to the out‐of‐plane radial buckling (R) mode and the in‐plane stretching modes of h‐BN in BNNTs, respectively, as well as weak features at 527, 576, and 1183 cm −1 consistent with known vibrational modes of T 1u (1), T 1u (2), and T 1u (3) symmetry in C 60 .…”

Section: Resultsmentioning

confidence: 99%

Growth of Carbon Nanotubes inside Boron Nitride Nanotubes by Coalescence of Fullerenes: Toward the World's Smallest Coaxial Cable

et al. 2017

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as excellent nanoscale containers for mole cules, [4][5][6] metals, [7][8][9] and metal halides, [10] where the spontaneous encapsulation is driven by van der Waals forces that stabilize the confined guest species in the internal channel of the host nanotube. [11] Moreover, a good geometric fit between the critical dimensions of the encapsulated guest and the internal dimensions of the host can result in van der Waals forces that are sufficiently high that insertion is irreversible. This effective nanoscale confinement permits the study of the structure, [12,13] motion, [14] and dynamics [15,16] of individual molecules.Furthermore, extreme spatial confinement in CNTs allows us to probe the kinetics and pathways of chemical reactions and processes at the nanoscale, including the formation of 1D materials templated by the internal channel of the host nanotube. [6,17,18] The simplest and most widely studied confined transformation in single-walled carbon nanotubes (SWCNTs) is the conversion of C 60 @SWCNT, so-called "peapods," into double-walled carbon nanotubes (DWCNTs) via the thermally activated polymerization and coalescence of guest fullerenes to an internal carbon nanotube. [17,19] Numerous more complex processes have also been observed inside nanotubes, such as unusual oligomerization and polymerization reactions, [13,20,21] the growth of graphene nanoribbons, [22][23][24] and the formation of molecular nanodiamonds [18] from encapsulated fullerenes and organic molecules, respectively. As such, chemical reactions inside carbon nanotubes open up new avenues for the synthesis of nanoscale materials with unique structures and functional properties inaccessible by other means.Boron nitride nanotubes (BNNTs) are isoelectronic to CNTs and similarly possess high mechanical strength [25] and excellent chemical and thermal stabilities. [26] In contrast to CNTs, however, BNNTs are electronically insulating, a consequence of the partly ionic interatomic BN bonding, and optically transparent with a wide bandgap. [27,28] While less well explored relative to CNTs, BNNTs represent a remarkable class of 1D nanoscale containers for metals, [29][30][31][32][33][34] metal halides, [35,36] and molecules, such as C 60 , [37] and owing to their transparency to visible light The use of boron nitride nanotubes as effective nanoscale containers for the confinement and thermal transformations of molecules of C 60 -fullerene is demonstrated. The gas-phase insertion of fullerenes into the internal channel of boron nitride nanotubes yields quasi-1D arrays, with packing arrangements of the guest fullerenes different from those in the bulk crystal and critically dependent on the internal diameter of the host nanotube. Interestingly, the confined fullerene molecules: i) exhibit dynamic behavior and temperaturedependent phase transitions analogous to that observed in the bulk crystal, and ii) can be effectively removed from within the internal channel of nanotubes by excessive sonication in organic solvent, indicating weak host-guest inter ...

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Section: Resultsmentioning

confidence: 99%

Growth of Carbon Nanotubes inside Boron Nitride Nanotubes by Coalescence of Fullerenes: Toward the World's Smallest Coaxial Cable

et al. 2017

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“…Consequently, carbon and boron nitride nanotubes have very different extinction coefficients of 45–55 and 1.64 × 10 –4 mL mg –1 cm –1 (at 204 nm), respectively, opening opportunities for probing electronic transitions of guest-molecules encapsulated within BNNTs with UV/visible light at least 270,000 times more effectively than in CNTs. Furthermore, the vibrational modes of guest-molecules are often obscured (“cloaked”) by the delocalized electron density of CNTs; as BNNTs have no delocalized charge carriers in the ground state, these vibrational modes are expected to become more accessible for molecules encapsulated within BNNTs. The transparent nature of BNNTs allows not only probing guest-molecules but also initiation of their photochemical reactions, as in the case of the polymerization of fullerene molecules in C 60 @BNNT triggered by visible light .…”

Section: Introductionmentioning

confidence: 99%

Host–Guest Chemistry in Boron Nitride Nanotubes: Interactions with Polyoxometalates and Mechanism of Encapsulation

et al. 2022

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Boron nitride nanotubes (BNNTs) are an emerging class of molecular container offering new functionalities and possibilities for studying molecules at the nanoscale. Herein, BNNTs are demonstrated as highly effective nanocontainers for polyoxometalate (POM) molecules. The encapsulation of POMs within BNNTs occurs spontaneously at room temperature from an aqueous solution, leading to the self-assembly of a POM@BNNT host–guest system. Analysis of the interactions between the host-nanotube and guest-molecule indicate that Lewis acid–base interactions between WO groups of the POM (base) and B-atoms of the BNNT lattice (acid) likely play a major role in driving POM encapsulation, with photoactivated electron transfer from BNNTs to POMs in solution also contributing to the process. The transparent nature of the BNNT nanocontainer allows extensive investigation of the guest-molecules by photoluminescence, Raman, UV–vis absorption, and EPR spectroscopies. These studies revealed considerable energy and electron transfer processes between BNNTs and POMs, likely mediated via defect energy states of the BNNTs and resulting in the quenching of BNNT photoluminescence at room temperature, the emergence of new photoluminescence emissions at cryogenic temperatures (<100 K), a photochromic response, and paramagnetic signals from guest-POMs. These phenomena offer a fresh perspective on host–guest interactions at the nanoscale and open pathways for harvesting the functional properties of these hybrid systems.

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Organic molecules encapsulated in single-walled carbon nanotubes

Cadena

Botka

2020

Oxford Open Materials Science

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Hybrid materials based on carbon nanotubes continue to attract considerable interest due to the broad variety of both the cages outside and the encapsulated species inside. This review focuses on organic molecules as guests in single-walled carbon nanotube hosts. The majority of results presented here have been attained in recent years by various methods of optical spectroscopy, complemented by transmission electron microscopy. These spectroscopic methods yield information on electronic structure, as well as dynamic processes as structural transformations and chemical reactions.

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Cloaking by π‐electrons in the infrared

Cited by 3 publications

References 8 publications

Growth of Carbon Nanotubes inside Boron Nitride Nanotubes by Coalescence of Fullerenes: Toward the World's Smallest Coaxial Cable

Growth of Carbon Nanotubes inside Boron Nitride Nanotubes by Coalescence of Fullerenes: Toward the World's Smallest Coaxial Cable

Host–Guest Chemistry in Boron Nitride Nanotubes: Interactions with Polyoxometalates and Mechanism of Encapsulation

Organic molecules encapsulated in single-walled carbon nanotubes

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