Carbon Nanotube Host Research Articles

Radical-Mediated Creation of Fluorescent Defects in Carbon Nanotubes

The fluorescent defects in carbon nanotubes have been demonstrated to give exceeding optical properties such as room temperature single photon emissions at telecom wavelengths. A handful of methods for creating these defects have been invented in the past 13 years and provides practical guidelines for obtaining desired functional groups. However, most reactions are performed in the aqueous solution, and the transfer of the single-wall carbon nanotubes (SWCNTs) from aqueous to organic solvents are usually challenging. This gives barriers for applications that require SWCNTs to be dissolved in an organic solvent. Here, we introduce controlled creations of three different fluorescent defects in carbon nanotube hosts in organic solvents using a single radical initiator. We achieved selective creations of benzyl, phenyl, and benzoyloxy defects by controlling the reaction conditions such as dissolved oxygen concentration, reaction temperature, solvents, and addition of radical scavengers. It is worth noting that the both radical initiator and solvent can provide functional groups at the defect sites through radical reaction. We believe that this method will serve as a practical platform for designing new fluorescent defects in the organic phase.

Unraveling the governing properties of confined carbyne through the interaction with its carbon nanotube host

Linear carbon chains (LCCs), synthesized using carbon nanotubes (CNTs) as templates, exhibit intriguing properties that are not dependent on their length. Consequently, LCCs can also be identified as carbyne. Since such carbyne only exists confined to CNT, it is commonly called confined carbyne (CC). In this study, we investigate the interaction between CC and double-walled CNTs (DWCNTs) through resonance Raman spectroscopy. The optical band gaps and Raman frequencies of inner (6,4) and (6,5) CNTs are influenced both externally by the outer CNTs and internally by the encapsulated CCs. Remarkably, our findings demonstrate that the properties of CC are determined by the interaction between the encapsulated CC and the CNT. As a result, the optical band gap of the encapsulated CC is solely dictated by the hosting CNT, rendering it identical to the host's gap. Therefore, we propose a novel approach to tailor the properties of CC by selecting the appropriate chirality of the CNT. These findings pave the way for future applications of CC with tailored properties, offering promising application opportunities of this material as semiconductor.

(Invited) Quantum Defects as Sensors

Organic color-centers are molecularly tunable quantum defects that can be synthetically introduced into semiconducting carbon nanotube hosts. Charge carriers in the form of electron-hole pairs (or excitons) are efficiently harvested at these atomic defect sites to emit as bright shortwave-infrared photons that carry local chemical information. These intriguing properties open new possibilities of pushing the limits of sensing and imaging. In this talk, we will discuss recent advances as well as the challenges and opportunities at this emerging frontier.

Can armchair nanotubes host organic color centers?

We use time-dependent density functional theory to investigate the possibility of hosting organic color centers in (6, 6) armchair single-walled carbon nanotubes, which are known to be metallic. Our calculations show that in short segments of (6, 6) nanotubes nm in length there is a dipole-allowed singlet transition related to the quantum confinement of charge carriers in the smaller segments. The introduction of defects to the surface of (6, 6) nanotubes results in new dipole-allowed excited states. Some of these states are redshifted from the native confinement state of the defect-free (6, 6) segments; this is similar behavior to what is observed with defects to exciton transitions in semiconducting carbon nanotubes. This result suggests the possibility of electrically wiring organic color centers directly through armchair carbon nanotube hosts.

A novel design of 3D carbon host for stable lithium metal anode

AbstractRational design of porous conductive hosts with high electrical conductivity, large surface area, and adequate interior space is desirable to suppressing dendritic lithium growth and accommodating large volume change of lithium metal anode during the Li plating/stripping process. However, due to the conductive nature of the conductive hosts, Li is easily deposited directly on the top of the hosts, which hinders it from fully functioning. To circumvent the issue, in this study, we designed a novel porous carbon host with a gradient‐pore‐size structure based on one‐dimensional (1D) carbon with different diameters. With this kind of host, stable cycling with high and stable Coulombic efficiency of ~98% is achieved at 0.5 mA cm−2 with an areal capacity of 1 mAh cm−2 over 320 cycles. In contrast, the normal three‐dimensional (3D) carbon nanotube host presents a moss‐like Li morphology with wildly fluctuating Coulombic efficiency after 100 cycles. The results reveal that the unique gradient‐pore‐size structure of the 3D conductive host greatly improves the performance of lithium metal batteries.

Encapsulation of an anticancer drug Isatin inside a host nano-vehicle SWCNT: a molecular dynamics simulation

The use of carbon nanotubes as anticancer drug delivery cargo systems is a promising modality as they are able to perforate cellular membranes and transport the carried therapeutic molecules into the cellular components. Our work describes the encapsulation process of a common anticancer drug, Isatin (1H-indole-2,3-dione) as a guest molecule, in a capped single-walled carbon nanotube (SWCNT) host with chirality of (10,10). The encapsulation process was modelled, considering an aqueous solution, by a molecular dynamics (MD) simulation under a canonical NVT ensemble. The interactions between the atoms of Isatin were obtained from the DREIDING force filed. The storage capacity of the capped SWCNT host was evaluated to quantify its capacity to host multiple Isatin molecules. Our results show that the Isatin can be readily trapped inside the volume cavity of the capped SWCNT and it remained stable, as featured by a reduction in the van der Waals forces between Isatin guest and the SWCNT host (at approximately − 30 kcal mol−1) at the end of the MD simulation (15 ns). Moreover, the free energy of encapsulation was found to be − 34 kcal mol−1 suggesting that the Isatin insertion procedure into the SWCNT occurred spontaneously. As calculated, a capped SWCNT (10,10) with a length of 30 Å, was able to host eleven (11) molecules of Isatin, that all remained steadily encapsulated inside the SWCNT volume cavity, showing a potential for the use of carbon nanotubes as drug delivery cargo systems.

Toward Confined Carbyne with Tailored Properties

Confining carbyne to a space that allows for stability and controlled reactivity is a very appealing approach to have access to materials with tunable optical and electronic properties without rival. Here, we show how controlling the diameter of single-walled carbon nanotubes opens the possibility to grow a confined carbyne with a defined and tunable band gap. The metallicity of the tubes has a minimal influence on the formation of the carbyne, whereas the diameter plays a major role in the growth. It has been found that the properties of confined carbyne can be tailored independently from its length and how these are mostly determined by its interaction with the carbon nanotube. Molecular dynamics simulations have been performed to interpret these findings. Furthermore, the choice of a single-walled carbon nanotube host has been proven crucial even to synthesize an enriched carbyne with the smallest energy gap currently reported and with remarkable homogeneity.

Organic molecules encapsulated in single-walled carbon nanotubes

Abstract 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 has 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.

Hidden Fine Structure of Quantum Defects Revealed by Single Carbon Nanotube Magneto-Photoluminescence.

Organic color-center quantum defects in semiconducting carbon nanotube hosts are rapidly emerging as promising candidates for solid-state quantum information technologies. However, it is unclear whether these defect color-centers could support the spin or pseudospin-dependent excitonic fine structure required for spin manipulation and readout. Here we conducted magneto-photoluminescence spectroscopy on individual organic color-centers and observed the emergence of fine structure states under an 8.5 T magnetic field applied parallel to the nanotube axis. One to five fine structure states emerge depending on the chirality of the nanotube host, nature of chemical functional group, and chemical binding configuration, presenting an exciting opportunity toward developing chemical control of magnetic brightening. We attribute these hidden excitonic fine structure states to field-induced mixing of singlet excitons trapped at sp3 defects and delocalized band-edge triplet excitons. These findings provide opportunities for using organic color-centers for spintronics, spin-based quantum computing, and quantum sensing.

Probing Trions at Chemically Tailored Trapping Defects.

Trions, charged excitons that are reminiscent of hydrogen and positronium ions, have been intensively studied for energy harvesting, light-emitting diodes, lasing, and quantum computing applications because of their inherent connection with electron spin and dark excitons. However, these quasi-particles are typically present as a minority species at room temperature making it difficult for quantitative experimental measurements. Here, we show that by chemically engineering the well depth of sp3 quantum defects through a series of alkyl functional groups covalently attached to semiconducting carbon nanotube hosts, trions can be efficiently generated and localized at the trapping chemical defects. The exciton-electron binding energy of the trapped trion approaches 119 meV, which more than doubles that of “free” trions in the same host material (54 meV) and other nanoscale systems (2–45 meV). Magnetoluminescence spectroscopy suggests the absence of dark states in the energetic vicinity of trapped trions. Unexpectedly, the trapped trions are approximately 7.3-fold brighter than the brightest previously reported and 16 times as bright as native nanotube excitons, with a photoluminescence lifetime that is more than 100 times larger than that of free trions. These intriguing observations are understood by an efficient conversion of dark excitons to bright trions at the defect sites. This work makes trions synthetically accessible and uncovers the rich photophysics of these tricarrier quasi-particles, which may find broad implications in bioimaging, chemical sensing, energy harvesting, and light emitting in the short-wave infrared.

Extraction of Linear Carbon Chains Unravels the Role of the Carbon Nanotube Host.

Linear carbon chains (LCCs) have been shown to grow inside double-walled carbon nanotubes (DWCNTs), but isolating them from this hosting material represents one of the most challenging tasks toward applications. Herein we report the extraction and separation of LCCs inside single-walled carbon nanotubes (LCCs@SWCNTs) extracted from a double-walled host LCCs@DWCNTs by applying a combined tip-ultrasonic and density gradient ultracentrifugation (DGU) process. High-resolution transmission electron microscopy, optical absorption, and Raman spectroscopy show that not only short LCCs but clearly long LCCs (LLCCs) can be extracted and separated from the host. Moreover, the LLCCs can even be condensed by DGU. The Raman spectral frequency of LCCs remains almost unchanged regardless of the presence of the outer tube of the DWCNTs. This suggests that the major importance of the outer tubes is making the whole synthesis viable. We have also been able to observe the interaction between the LCCs and the inner tubes of DWCNTs, playing a major role in modifying the optical properties of LCCs. Our extraction method suggests the possibility toward the complete isolation of LCCs from CNTs.

Frontispiece: Photochemical Creation of Fluorescent Quantum Defects in Semiconducting Carbon Nanotube Hosts

Frontispiece: Photochemical Creation of Fluorescent Quantum Defects in Semiconducting Carbon Nanotube Hosts

Frontispiz: Photochemical Creation of Fluorescent Quantum Defects in Semiconducting Carbon Nanotube Hosts

Frontispiz: Photochemical Creation of Fluorescent Quantum Defects in Semiconducting Carbon Nanotube Hosts

Photochemical Creation of Fluorescent Quantum Defects in Semiconducting Carbon Nanotube Hosts

AbstractQuantum defects are an emerging class of synthetic single‐photon emitters that hold vast potential for near‐infrared imaging, chemical sensing, materials engineering, and quantum information processing. Herein, we show that it is possible to optically direct the synthetic creation of molecularly tunable fluorescent quantum defects in semiconducting single‐walled carbon nanotube hosts through photochemical reactions. By exciting the host semiconductor with light that resonates with its electronic transition, we find that halide‐containing aryl groups can covalently bond to the sp2 carbon lattice. The introduced quantum defects generate bright photoluminescence that allows tracking of the reaction progress in situ. We show that the reaction is independent of temperature but correlates strongly with the photon energy used to drive the reaction, suggesting a photochemical mechanism rather than photothermal effects. This type of photochemical reactions opens the possibility to control the synthesis of fluorescent quantum defects using light and may enable lithographic patterning of quantum emitters with electronic and molecular precision.

Photochemical Creation of Fluorescent Quantum Defects in Semiconducting Carbon Nanotube Hosts.

Quantum defects are an emerging class of synthetic single-photon emitters that hold vast potential for near-infrared imaging, chemical sensing, materials engineering, and quantum information processing. Herein, we show that it is possible to optically direct the synthetic creation of molecularly tunable fluorescent quantum defects in semiconducting single-walled carbon nanotube hosts through photochemical reactions. By exciting the host semiconductor with light that resonates with its electronic transition, we find that halide-containing aryl groups can covalently bond to the sp2 carbon lattice. The introduced quantum defects generate bright photoluminescence that allows tracking of the reaction progress in situ. We show that the reaction is independent of temperature but correlates strongly with the photon energy used to drive the reaction, suggesting a photochemical mechanism rather than photothermal effects. This type of photochemical reactions opens the possibility to control the synthesis of fluorescent quantum defects using light and may enable lithographic patterning of quantum emitters with electronic and molecular precision.

Porous carbon nanotubes improved sulfur composite cathode for lithium-sulfur battery

Porous multi-walled carbon nanotubes (PCNTs) with multiple mesopores structure are synthesized through activation of multi-walled carbon nanotubes (MWCNTs) by potassium hydroxide. The potassium hydroxide activation process results in a significantly enhanced specific surface area with numerous small pores. The as-obtained PCNTs are employed as the conductive matrix for sulfur in the sulfur cathode. Compared with the composite sulfur cathode based on the original MWCNTs, the sulfur-PCNTs cathode shows a significantly improved cycle performance and columbic efficiency. The reversible capacity is 530 mAh g−1 and columbic efficiency is 90 % after 100 cycles at a current density of 100 mA g−1. The improvement in the electrochemical performance for S-PCNT is mainly attributed to the enlarged surface area and the porous structure of the unique mesopores carbon nanotube host, which cannot only facilitate transport of electrons and Li+ ions, but also trap polysulfides, retard the shuttle effect during charge/discharge process.

Two-Dimensional Coalescence Dynamics of Encapsulated Metallofullerenes in Carbon Nanotubes

We report on the coalescence of a two-dimensional (2D) chain of La@C(82) metallofullerene molecules encapsulated inside a single-wall carbon nanotube (SWNT). 2D packing of metallofullerenes is known to adopt a zigzag arrangement and cause elliptical distortion to the cross-section of the SWNT host. We show that after coalescence of the metallofullerenes into an inner nanotube the carbon nanotube host returns to its original circular cross-section. This is due to a relaxation of the strain caused by the packing of the encapsulated La@C(82) molecules into the nanotube. We identify the formation of some novel but transient fullerene-based structures formed during the intermediate stages of coalescence of the La@C(82) into an inner nanotube. These results highlight the flexible nature of SWNTs and their ability to adapt their cross-sectional profile depending upon forces induced by material encapsulated within.

The BN-pair impurity in carbon nanotubes and the possibility for disorder-inducedfrustration of gap formation

We study the BN-pair impurity complex inside a metallic and a semiconductingsingle-walled carbon nanotube host. For the single impurity in the semiconductingtube, we find that no electron or hole bound states can be sustained because thedistance between the B and the N is less than the effective Fermi–Teller radius forthat system. If the BN pairs are incorporated at stoichiometric concentrations(BC10N nanotubes), achievable for example with a borabenzene–pyridine adductC10H10BN precursor, the metallic tube becomes semiconducting for an ordered arrangement of theimpurities, but the introduction of disorder restores a finite density of states at the Fermilevel. Thus, in the mechanism presented here, disorder effectively restores thesymmetry of the nanotube, returning the nanotube to its original metallic character.

Growth of single wall carbon nanotubes from 13C isotope labelled organic solvents inside single wall carbon nanotube hosts

We present the growth of single wall carbon nanotubes (SWCNTs) from organic solvents such as benzene and toluene inside a host SWCNT. The solvents encapsulated in SWCNTs are transformed to an inner tube when subject to a heat treatment under dynamic vacuum at 1270 °C. We used isotope labeling of the different carbon sources to prove that the source of the inner tubes is indeed the solvent. Our results put constraints on the models explaining the inner tube growth and provides a simple alternative for the fullerene based inner tube growth. It also provides the possibility to study a completely new field of in-the-tube chemistry.

Temperature dependence of conductance character in nanotube peapods

Recent electrical transport measurements on metallofullerene-doped nanotube peapods are reviewed. In temperature-dependent conductance measurements, it was found that the temperature plays a crucial role in charge transfer between the nanotube and entrapped metallofullerenes and it is shown that the metallofullerenes can function as electron donors and transfer charge to the carbon nanotube host. The amount of charge transferred varies with temperature. At room temperature, the doped nanotube shows p-type conduction. As the temperature decreases, the conductance becomes n-type and even metallic behavior is observed at still lower temperatures, indicating the degenerate state caused by doping.