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During the last 30 years, theoretical scientists imagined segmental families of monolayer carbon tubules with fullerene-based end-caps. These fullertube molecules would possess structural features of both fullerenes (hemispherical end-caps) and tubular belts of single-walled carbon nanotubes (SWCNTs). Yet, their experimental verification remained elusive for decades. It was not until 2020–2023 that segmental families of fullertubes were finally confirmed in the lab. The shocking irony is that these fullertubes were unwittingly coproduced alongside fullerenes (e.g., C60, C70, C84) in both flame and electric arc soot since the 1990s. Yet, nobody knew these “hidden” families of fullertubes were experimentally present in their extracted soot due to their low abundance and the absence of isolation methodology. This eruption of fullertube discoveries in 2020–2023 was brought to fruition by structural data, both DFT and experimental. This “Treasure Trove” of new molecules during this four-year window occurred with only microgram quantities. Typically, milligram levels of purified samples are required for X-ray crystallography and 13C NMR structural analysis. The breakthrough for experimentally verifying the missing fullertubes was an aminopropanol reagent to selectively react with and remove spheroidal carbon (e.g., C60, C70, C84) as hydrophilic derivatives. In contrast, there was suppressed reaction with fullertubes, which remained in organic solvent. It is well established that high symmetry (3-, 5-, and 6-fold) hemispheres for C60-Ih and other fullerenes and metallofullerenes are prerequisite end-caps for fullertubes. For the case of [5,5] C130 fullertubes, this requirement results in only eight 3-, 5-, and 6-fold symmetry structural isomers possible from a total of 39,393 possible isolated pentagon rule (IPR) isomers. From this C130 list of 8 candidate isolated pentagon rule (IPR) high symmetry isomers, surprisingly only one structure matched the DFT polarizability versus chromatographic retention parameter (a new gold standard for isomer identification). The simultaneous emergence of DFT computations of other properties (e.g., total energy, HOMO–LUMO gap, UV–vis) for large carbon molecules provided support for structural determination. Experimental approaches (e.g., mass spectrometry, UV–vis, XPS, Raman, and STEM) provided additional layers of structural elucidation at the microgram level. For the first time, we developed a chemical isolation protocol that would allow the preparation and isolation of soluble pristine fullertubes in the range of C90–C200. To date, applications of SWCNTs for use in nanoscale computer applications requires purities greater than 99.999%. Although this stringent mandate has not yet been demonstrated using SWCNT samples, this high level of purity appears achievable for metallic [5,5] D5d-C120 and semiconductor [10,0] D5h-C120 [10,766] fullertubes. Moreover, commercial production of pristine fullertubes should easily be feasible by the flame method due to its continuous operation and inexpensive feedstock. For application development, theoretical and electrochemical experimental data show that fullertubes exhibit high catalytic activity in oxygen reduction reactions. In the medical sector, pristine fullertube dispersions exhibit antimicrobial effects on Mycobacterium smegmatis and M. abscessus. 

The retention behavior of fullerenes and fullertubes on a PYE column in reversed-phase chromatography was investigated to clarify the influence of their shapes on the separation process. The impact of anisotropy was further elucidated using a pair potential interaction model, together with experimental data and ab initio calculations, to evaluate its contribution to various parameters characterizing the interaction models. The findings indicate that the shape of fullerenes plays a more significant role than anticipated in the retention mechanisms, highlighting the necessity of considering the shape of fullerenes and fullertubes to accurately predict their retention times. Furthermore, a phenomenological pair potential was devised to demonstrate the feasibility of precisely predicting the retention times of fullerenes and fullertubes through first-principles calculations, regardless of their shape. The existence of such a model paves the way for the development of a method to identify isomers of fullerenes from minute amounts of sample. 

Abstract Endohedral metallofullerenes are chemically more inert compared to empty fullerenes, primarily due to their intramolecular electron transfer. In this work, we report an inverse electron demand Diels–Alder (IEDDA) reaction on M₃N@C₈₀(M=Lu, Sc), where they show significantly higher reactivity than empty fullerenes. The molecular structures of the [4+2] cycloadducts were unambiguously characterized. Moreover, the cycloadducts can fully revert to pristine M₃N@C₈₀via retro‐cycloaddition upon thermal treatment. With the unusual reactivity and reversibility, the IEDDA reaction enables an effective separation approach for metallofullerenes from their soot extracts, opening path to efficient and economical scale‐up synthesis of metallofullerenes in laboratory and industrial settings. 

Mycobacterium tuberculosis and nontuberculous mycobacteria such as Mycobacterium abscessus cause diseases that are becoming increasingly difficult to treat due to emerging antibiotic resistance. The development of new antimicrobial molecules is vital for combating these pathogens. Carbon nanomaterials (CNMs) are a class of carbon-containing nanoparticles with promising antimicrobial effects. Fullertubes (C90) are novel carbon allotropes with a structure unique among CNMs. The effects of fullertubes on any living cell have not been studied. In this study, we demonstrate that pristine fullertube dispersions show antimicrobial effects on Mycobacterium smegmatis and M. abscessus. Using scanning electron microscopy, light microscopy, and molecular probes, we investigated the effects of these CNMs on mycobacterial cell viability, cellular integrity, and biofilm formation. C90 fullertubes at 1 µM inhibited mycobacterial viability by 97%. Scanning electron microscopy revealed that the cell wall structure of M. smegmatis and M. abscessus was severely damaged within 24 h of exposure to fullertubes. Additionally, exposure to fullertubes nearly abrogated the acid-fast staining property of M. smegmatis. Using SYTO-9 and propidium iodide, we show that exposure to the novel fullertubes compromises the integrity of the mycobacterial cell. We also show that the permeability of the mycobacterial cell wall was increased after exposure to fullertubes from our assays utilizing the molecular probe dichlorofluorescein and ethidium bromide transport. C90 fullertubes at 0.37 µM and C60 fullerenes at 0.56 µM inhibited pellicle biofilm formation by 70% and 90%, respectively. This is the first report on the antimycobacterial activities of fullertubes and fullerenes. 

Abstract Fullertubes, that is, fullerenes consisting of a carbon nanotube moiety capped by hemifullerene ends, are emerging carbon nanomaterials whose properties show both fullerene and carbon nanotube (CNT) traits. Albeit it may be expected that their electronic states show a certain resemblance to those of the extended nanotube, such a correlation has not yet been found or described. Here it shows a scanning tunneling microscopy (STM) and spectroscopy (STS) characterization of the adsorption, self‐assembly, and electronic structure of 2D arrays of [5,5]‐C₉₀ fullertube molecules on two different noble metal surfaces, Ag(111) and Au(111). The results demonstrate that the shape of the molecular orbitals of the adsorbed fullertubes corresponds closely to those expected for isolated species on the grounds of density functional theory calculations. Moreover, a comparison between the electronic density profiles in the bands of the extended [5,5]‐CNT and in the molecules reveals that some of the frontier orbitals of the fullertube molecules can be described as the result of the quantum confinement imposed by the hemifullerene caps to the delocalized band states in the extended CNT. The results thus provide a conceptual framework for the rational design of custom fullertube molecules and can potentially become a cornerstone in the understanding of these new carbon nanoforms. 

We report the seminal experimental isolation and DFT characterization of pristine [5,5] C130-D5h(1) fullertubes. This achievement represents the largest soluble carbon molecule obtained in pristine form. The [5,5] C130 species is the highest aspect ratio fullertube purified to date and now surpasses the recent gigantic [5,5] C120-D5d(1). In contrast to C90, C100, and C120 fullertubes, the longer C130-D5h has more nanotubular carbons (70) than end-cap fullerenyl atoms (60). Starting from 39,393 possible C130 isolated pentagon rule (IPR) structures and after analyzing polarizability, retention time, and UV-vis spectra, these three layers of data remarkably predict a single candidate isomer and fullertube, [5,5] C130-D5h(1). This structural assignment is augmented by atomic resolution STEM data showing distinctive and tubular “pill-like” structures with diameters and aspect ratios consistent with [5,5] C130-D5h(1) fullertubes. The high selectivity of the aminopropanol reaction with spheroidal fullerenes permits a facile separation and removal of fullertubes from soot extracts. Experimental analyses (HPLC retention time, UV-vis, and STEM) were synergistically used (with polarizability and DFT property calculations) to down select and confirm the C130 fullertube structure. Achieving the isolation of a new [5,5] C130-D5h fullertube opens the door to application development and fundamental studies of electron confinement, fluorescence, and metallic character for a fullertube series of molecules with systematic tubular elongation. This [5,5] fullertube family also invites comparative studies with single-walled carbon nanotubes (SWCNTs), nanohorns (SWCNHs), and fullerenes. 

Fullertubes are tubular fullerenes with nanotube-like middle section and fullerene-like endcaps. To understand how this intermediate form between spherical fullerenes and nanotubes is reflected in the vibrational modes, we performed comprehensive studies of IR and Raman spectra of fullertubes C90-D5h, C96-D3d, and C100-D5d. An excellent agreement between experimental and DFT-computed spectra enabled a detailed vibrational assignment and allowed an analysis of the localization degree of the vibrational modes in different parts of fullertubes. Projection analysis was performed to establish an exact numerical correspondence between vibrations of the belt midsection and fullerene headcaps to the modes of nanotubes and fullerene C60-Ih. As a result, we could not only identify fullerene-like and CNT-like vibrations of fullertubes, but also trace their origin in specific vibrational modes of CNT and C60-Ih. IR spectra were found to be dominated by vibrations of fullerene-like caps resembling IR-active modes of C60-Ih, whereas in Raman spectra both caps and belt vibrations are found to be equally active. Unlike the resonance Raman spectra of CNTs, in which only two single-phonon bands are detected, the Raman spectra of fullertubes exhibit several CNT-like vibrations and thus provide additional information on nanotube phonons. 

We report the first experimental characterization of isomerically pure and pristine C120 fullertubes, [5,5] C120-D5d(1) and [10,0] C120-D5h(10766). These new molecules represent the highest aspect ratio fullertubes isolated to date; for example, the prior largest empty cage fullertube was [5,5] C100-D5d(1). This increase of 20 carbon atoms represents a gigantic leap in comparison to three decades of C60–C90 fullerene research. Moreover, the [10,0] C120-D5d(10766) fullertube has an end-cap derived from C80-Ih and is a new fullertube whose C40 end-cap has not yet been isolated experimentally. Theoretical and experimental analyses of anisotropic polarizability and UV–vis assign C120 isomer I as a [5,5] C120-D5d(1) fullertube. C120 isomer II matches a [10,0] C120-D5h(10766) fullertube. These structural assignments are further supported by Raman data showing metallic character for [5,5] C120-D5d(1) and nonmetallic character for C120-D5h(10766). STM imaging reveals a tubular structure with an aspect ratio consistent with a [5,5] C120-D5d(1) fullertube. With microgram quantities not amenable to crystallography, we demonstrate that DFT anisotropic polarizability, augmented by long-accepted experimental analyses (HPLC retention time, UV–vis, Raman, and STM) can be synergistically used (with DFT) to down select, predict, and assign C120 fullertube candidate structures. From 10 774 mathematically possible IPR C120 structures, this anisotropic polarizability paradigm is quite favorable to distinguish tubular structures from carbon soot. Identification of isomers I and II was surprisingly facile, i.e., two purified isomers for two possible structures of widely distinguishing features. These metallic and nonmetallic C120 fullertube isomers open the door to both fundamental research and application development.