C20 Fullerene Research Articles

Ab initio simulation of the effects of substitutional doping of oxygen in the semifullerene (C30)

Using first principles calculations, we studied the effects of substitutionally doping a 30-atom semifullerene (C30) with oxygen atoms, within the Density Functional Theory (DFT) and the pseudopotential formalism. We analyzed two C30 structures, one with a pentagonal and one with a hexagonal base. In both cases, the substitutionally absorbed oxygen atoms break the bonds between pentagons and hexagons of the semifullerene. We show that each semifullerene breaks into two geometrically flat structures, one of them being consistent with a known ring isomer of the fullerene C20. We used the Quantum ESPRESSO package code and the generalized gradient corrected Perdew-Burke-Ernzerhof (PBE) approximation for the exchange and correlation functional.

Spin-polarized electrical transport in transition metal encapsulated C20 fullerenes: A theoretical account

This work delves into the conductance property of transition metal (Ti, V, Cr, Mn, Fe, Co, Ni) encapsulated C20 endohedral metallofullerenes (EMFs), sandwiched between non-magnetic gold electrodes. DFT optimization of the designed systems casts the encapsulated metal at the center of the C20 cage irrespective of the system and spin states. Application of density functional theory coupled with non-equilibrium green function techniques on these EMFs results variant transport characteristics for different metal encapsulation, represented through transmission spectra at zero bias and current vs. voltage (I-V) plots. Spin-polarized electrical transport has been observed for the Mn, Fe, Co and Ni encapsulated C20, while no such spin polarization could be traced for Ti, V and Cr both in absence and presence of applied bias. The EMFs with Mn, Fe, Co and Ni display half-metallic behavior and significant spin-filtering efficiency, which reaches maximum value for the Fe encapsulated C20. Spin-resolved electrical conductance in the Mn/Fe/Co/Ni-EMFs are explained by density of states, projected density of states at zero bias and molecular orbital analyses, which reveal the contribution of C20 electrons towards the down-spin-polarized transmission for Fe/Co/Ni-EMFs, while for the Mn-EMF, the metal d-electrons mostly participate in the up-spin-polarized transmission. Taken these observations together, the present computational study showcases the importance of encapsulating transition metal inside carbon cages in inducing spin polarization and thus provides an aid to tailor suitable molecules for spintronic applications.

The key feature of instability of small non-IPR closed-shell fullerenes: three isomers of C40

The molecular structures of non-IPR C40 fullerene isomers 31 (Cs), 38 (D2) and 39 (D5d) were studied using a semiempirical approach developed earlier for higher fullerenes. Quantumchemical calculations (DFT) showed that they have closed shells. The distributions of single, double and delocalized π bonds in the test isomer molecules and their molecular formulas are presented for the first time.

1,3-Dioxane inside fullerenes: the innovative conformational behavior of usual cyclic system

Conformational transformations of unsubstituted 1,3-dioxane in the cavities of fullerenes with 60, 70 and 80 atoms in their shells have been investigated using PBE/3ζ density functional theory method. It was shown that the preferred conformation of the guest molecule in endoclasters with 60 atoms (С60, С12B24N24, B36N24) corresponds to the 1,4-twist form, not to the expected chair. In case of fullerenes C70 and C80 conformational equilibrium is shifted to the chair, but the relative stability of 1,4-twist-form is higher in comparison with free 1.3-dioxane. Substitution carbon atoms of the last nanostructures by boron-nitrogen fragments again resulted in the dominance of 1,4-twist conformer. In all cases the molecule of 1,3-dioxane inside fullerenes has a notable electric charge and demonstrates a significant reduction in bond lengths.

Структура молекулы изомера 17894 (С1) фуллерена C76: причины её нестабильности и вероятные пути стабилизации

It is well-known that non-IPR fullerenes are highly unstable. For this reason, they cannot be obtained as pristine fullerenes; however, some of them become stable as derivatives (exohedral or endohedral). In this article, we attempted to elucidate in detail molecular structure for such a non-IPR fullerene. Using theoretical approach supported by DFT calculations, the features of molecular structure of isomer 17894 (C1) of fullerene C76 with data about distribution of single, double and delocalized π-bonds as well its structural formula has been determined for the first time. The instability of the studied fullerene molecule caused by its open-shell structure and significant local overstrains related to the high folding angle value of pentagons in pentalene fragment. The supposed synthesis of the endohedral molecule starts with the ionic pair formation, i.e. anionic fragment of fullerene cage and metal cation electrostatically bound with it. It would lead to closing of open electron shell of fullerene and local overstrain release at pentalene fragment. As to the exohedral derivatives the probable positions of addends are discussed. Both methods in their own demonstrate the possibilities to stabilize the molecule of the C76 isomer 17894. The elucidation and analysis of structural features along with electronic characteristics of non-IPR fullerene molecules appear to be useful for predicting the possibility of their synthesis as derivatives and will assist in determination of their reactivity. This will ensure the targeted production of fullerenes and their derivatives for the needs of medicine, electronics and other industries. The fundamental knowledge of the properties of nanoobjects, namely fullerenes, is actually developing as the independent direction with a long-term perspective.

Ultrafast rattling motion of a single atom in a fullerene cage sensed by terahertz spectroscopy

We have investigated the dynamical motion of a single Ce atom encapsulated in a C82 fullerene cage (Ce@C82) by using terahertz (THz) spectroscopy. A Ce@C82 molecule is placed in a sub-nm gap of metal electrodes and excited by THz radiation. Two broad peaks are observed in the THz photocurrent spectra around 5 meV and 15 meV and are attributed to the lateral and longitudinal vibrational modes of the encapsulated single Ce atom, respectively. The present results demonstrate that the THz spectroscopy using nanogap electrodes has an extremely high sensitivity that can detect the dynamical motion of a single atom.

Different molecular arrangements to capture fullerene by aromatic systems

ABSTRACT Direct reactions to generate covalent or coordinated bonds as well as π stacking interactions are theoretically studied in order to suggest which can be the best pathway to achieve fullerene capture by means aromatic fragments. The chosen models include isolated coronene and 1,4,5,8-Naphtalenetetracarboxdiimide as well as the mentioned species included into macrocycles. The nature of the formed bond and the frontier molecular orbitals are studied and the particular pathway which generates a covalent bond with a fullerene C20 is also analysed.

DFT study for Structural and Electronic Properties of N2O3 Adsorption onto C20 Fullerene

Structural and electronic properties of N2O3 adsorbed on C20 fullerene were investigated by Density Functional Theory. Before N2O3 was adsorbed on C20 fullerene surface, the structural properties of the isomers of the N2O3 were calculated. According to the total energy calculations, asym-N2O3 is the most stable isomer since it has lower energy than the other two isomers. Data obtained for the structural properties of N2O3 molecule are in agreement with the previous studies. After full structural optimization without any restrictions, the most stable structures were obtained. The adsorption energies with no dissociation of N2O3 were in the range of −2.88 to −3.55 eV for LDA and −2.02 to −2.45 eV for GGA. On the other hand, the dissociative adsorption yields a lower total energy with Eads values of −3.72 and −2.93 eV in LDA and GGA, respectively. According to these values, adsorption can be evaluated as chemisorption for all stable structures. The adsorption occurs with no reaction barriers except for one configuration. Although the co-adsorption of NO and NO2 molecules on the same fullerene is energetically less favorable compared to their adsorptions on separate fullerenes, the dissociative co-adsorption occurs with no energy barrier. The electronic structures are dominated by charge transfer from the fullerene to the adsorbate. The obtained HOMO-LUMO gap (GapHL) values are in the range of 1.02 and 1.35 eV for both LDA and GGA, respectively. The results presented here can be expected to guide future experimental and theoretical studies as new hybrid material.

Исследование процесса адсорбции фуллеренов С20 на поверхности углеродных нанотрубок для создания наномеханических комплексов

Исследование процесса адсорбции фуллеренов С20 на поверхности углеродных нанотрубок для создания наномеханических комплексов

Fullerene Thermochemical Stability: Accurate Heats of Formation for Small Fullerenes, the Importance of Structural Deformation on Reactivity, and the Special Stability of C60.

We have used quantum chemistry computations, in conjunction with isodesmic-type reactions, to obtain accurate heats of formation (HoFs) for the small fullerenes C20 (2358.2 ± 8.0 kJ mol-1), C24 (2566.2 ± 7.6), and the lowest-energy isomers of C32 (2461.1 ± 15.4), C42 (2629.0 ± 20.5), and C54 (2686.2 ± 25.3). As part of this endeavor, we have also obtained accurate HoFs for several medium-sized molecules, namely 216.6 ± 1.4 for fulvene, 375.5 ± 1.5 for pentalene, 670.8 ± 2.9 for acepentalene, and 262.7 ± 2.5 for acenaphthylene. We combine the energies of the small fullerenes and previously obtained energies for larger fullerenes (from C60 to C6000) into a full picture of fullerene thermochemical stability. In general, the per-carbon energies can be reasonably approximated by the "R+D" model that we have previously developed [Chan et al. J. Chem. Theory Comput. 2019, 15, 1255-1264], which takes into account Resonance and structural Deformation factors. In a case study on C54, we find that most of the high-deformation-energy atoms correspond to the sites of the C-Cl bond in the experimentally captured C54Cl8. In another case study, we find that C60 has the lowest value for the maximum local-deformation energy when compared with similar-sized fullerenes, which is consistent with its "special stability". These results are indicative of structural deformation playing an important role in the reactivity of fullerenes.

Confinement Effects of a Noble Gas Dimer Inside a Fullerene Cage: Can It Be Used as an Acceptor in a DSSC?

A detailed density functional theory investigation of He2-encapsulated fullerene C36 and C40 has been presented here. When confinement takes place, He-He bond length shortens and a non-covalent type of interaction exists between two He atoms. Energy decomposition analysis shows that though an attractive interaction exists in free He2, when it is confined inside the fullerenes, repulsive interaction is observed due to the presence of dominant repulsive energy term. Fullerene C40, with greater size, makes the incorporation of He2 much easier than C36 as confirmed from the study of boundary crossing barrier. In addition, we have studied the possibility of using He2-incorporated fullerene as acceptor material in dye-sensitized solar cell (DSSC). Based on the highest energy gap, He2@C40 and bare C40 fullerenes are chosen for this purpose. Dye constructed with He2@C40 as an acceptor has the highest light-harvesting efficiency and correspondingly will possess the maximum short circuit current as compared to pure C40 acceptor.

Isolation and crystal structure of the trifluoromethyl derivative C84(24)(CF3)18 of a minor C84 fullerene isomer

C1-C84(24)(CF3)18 was isolated by HPLC from the trifluoromethylation products of a C84 fullerene mixture. Its molecular structure was determined by single crystal X-ray diffraction using synchrotron radiation. In the addition pattern, 18 CF3 groups are arranged near the cage equator, thus isolating five benzenoid rings and three C=C bonds on the carbon cage.

Aminated C20 fullerene as a promising nanosensor for detection of A-234 nerve agent

In this study, we investigated the interaction of A-234 molecule with the pristine, Si, Ge, Sc doped and aminated C20 fullerene using density functional theory (DFT). Adsorption of A-234 molecule on pristine C20 fullerene provides insufficient adsorption energy (-5.27 kcal.mol−1) which makes it unsuitable sensor platform for detection of this molecule. When A-234 molecule is adsorbed on Si, Ge and Sc doped fullerene, the work function (Φ) alters properly (-18.78%, −25.69% and −70.43%, respectively). However, adsorption energies are very high (-104.16, −96.19 and −76.05 kcal.mol−1, respectively). In contrast, when a A-234 molecule is adsorbed from its PO head on the C20HNH2 (aminated) fullerene, its work function is considerably decreased (−12.20%) demonstrating a appropriate sensitivity and the adsorption energy (−13.55 kcal.mol−1) is small enough to provide short recovery time. In addition, the electron emission greatly increases which can be converted to an electronic noise and thus, C20HNH2 fullerene is a work function-type sensor for sensing and detection of A-234 nerve agent.

Scandium Tetrahedron Supported by H Anion and CN Pentaanion inside Fullerene C80.

Endohedral metallofullerenes have greatly expanded the range of the fullerene family due to their nesting structure and unusual encapsulated clusters protected by a fullerene cage. Herein, we report a metallofullerene Sc4CNH@Ih-C80, which has a scandium tetrahedron supported by H and CN anions inside fullerene C80. Sc4CNH@Ih-C80 has a rare multilayer nesting structure, and the internal Sc4CNH is the most complex endohedral cluster disclosed to date. Sc4CNH@Ih-C80 has so many bonding types (metal-carbide, metal-nitride, and metal-hydride), which weave a polyhedron of Sc4CNH clusters. This work shows that the endohedral metallofullerenes have the potential to build inorganic nesting polyhedra that have distinctive architectures and unique electronic properties. Sc4CNH@Ih-C80 was synthesized by means of the arc-discharge method using scandium and graphite under the mixed atmosphere of hydrogen, nitrogen, and helium. It is the first time to disclose an unprecedented metal-hydride bond in a fullerene cage. This result shows that the endohedral fullerenes bearing hydrogen species can be synthesized by the arc-discharge technique under an atmosphere of hydrogen. This work demonstrates that a fullerene cage can be an ample carrier to encapsulate unusual cluster moieties.

C20 fullerene and its boron- and nitrogen-doped counterparts as an efficient catalyst for CO oxidation

DFT calculations are utilised to investigate the CO oxidation on the C20, BC19, and NC19 clusters. For CO oxidation over considered clusters, two continuous steps are proposed that in each step one CO2 molecule is released from clusters surface. The calculations demonstrate that in the case of the C20 cluster, the first step of CO oxidation takes place through the ER mechanism on two routes with a barrier height of 1.06 eV and 2.57 eV for the rate-limiting step. Also, in the cases of BC19 and NC19 clusters, both reaction paths occur via the ER mechanism. The activation energy of the first reaction step is about 0.53 and 0.46 eV, while it is negligible for the second step that is 0.04 and 0.18 eV for BC19 and NC19 clusters, respectively. Based on the present theoretical results, the catalytic activity of BC19 and NC19 clusters toward the CO oxidation is more than that of the C20 cluster. These results show that the BC19 and NC19 clusters can be recommended as an efficient and metal-free catalyst for CO oxidation at near ambient temperatures. Research Highlights CO oxidation over C20 fullerene has been investigated. The effect of N/B-doing on the CO oxidation reaction is also studied. The N/B-doping increases the catalytic activity of C20 fullerene. Boron/Nitrogen-doped C20 fullerene can be applied as an efficient catalyst for CO oxidation.

TDDFT Study of the Influence of C20 Fullerene on Optical Properties of BODIPY and Two its Analogs: AlDIPY, GaDIPY

In this research, it is tried to improve electrical, optical, and non-linear optical (NLO) properties of boron-dipyrromethene (BODIPY) as a very optically active molecule. The results showed that two analogs of BODIPY, i.e., the AlDIPY and GaDIPY, have electrical properties and optical activity comparable to those of BODIPY. Next, improvement of the electrical and optical properties of BODIPY, AlDIPY, and GaDIPY was investigated using the C20 fullerene, as an electronegative fragment, instead of two F atoms. The results showed considerable improvement in the electrical properties of these molecules. Compatible with high electronegativity of C20 fullerene, evident charge transfer (CT) from BODIPY, AlDIPY, and GaDIPY to C20 fullerene was seen. Promising results were observed when using the C20 to modify the optical properties of BODIPY, AlDIPY, and GaDIPY. In particular, the optical properties of BODIPY were enriched in the presence of C20. This molecule causes the creation of two absorption lines in visible region that did not exist before. The solvent influence on the optical activity of BODIPY-C20 showed that, in the visible region, the λmax line is affected by the polarity of the solvent and increasing solvent dielectric constant cause a blue shift in this region. Finally, the NLO properties were calculated for all mentioned molecules, which indicated remarkable improvement in the NLO properties in the presence of C20 fullerene. The results of this research showed that the designed molecules are suitable for photosensitizer uses because of their NLO properties.

Structure, stability, MEP, NICS, reactivity, and NBO of Si–Ge nanocages evolved from C20 fullerene at DFT

We have performed systematic theoretical studies of C20 and its SinGenC20-2n heterofullerenic derivatives with n = 1–10, at the density functional theory. Vibrational frequency analysis confirms that except for Si5Ge5C10, Si8Ge8C4, and Si10Ge10, other systems are true minima and none of the 12 computed heterofullerenes collapses to open deformed as segregated nanocage. Isolating the Si–Ge hetero bonds through C=C double bond and/or one carbon atom is an appropriate approach for reaching highly substituted stable heterofullerenes, since it prevents weak Si–Si and Ge–Ge homo bonds. The calculated band gap, ionization potential, and atomization energy of Si1Ge1C18 shows it as the best insulated heterofullerene. Binding energy, and absolute values of heat of atomization of computed heterofullerene decrease as number of substituting Si–Ge unit increases. Henceforth, in contrast to the common belief that thermodynamically stable species are not always kinetically stable, here isolable or extractable Si1Ge1C18 heterofullerene is stable from both viewpoints. Contrary, Si10Ge10 that unfortunately suffers from lack of carbon participation, is revealed as the most chemically reactive heterofullerene and the best optically active via increasing its hyperpolarizability. Exclusive of Si10Ge10, substitutional doping of other heterofullerenes leads to a high NBO charge distribution upon their surfaces. We are very pleased to state that isolating the Si–Ge single bonds by intermediation of only one carbon atom is an applicable strategy for obtaining the highest atomic charge distributions on C, Si, and Ge atoms of Si6Ge6C8 as suitable hydrogen storage. Evaluating nucleus independent chemical shift (NICS) values at the cage centers clearly show the highest aromatic character of Si1Ge1C18 species followed by Si2Ge2C16 (− 48.76 and − 35.42 ppm compared to − 19.61 for the pure carbon cage, C20).

Investigation of structural and electronic properties of N2O4 adsorbed on C20 fullerene

We report density functional theory calculations for structural and electronic properties of N2O4 adsorbed on C20 fullerene. At the beginning of the study, the isomers of N2O4 molecule were obtained and their structural properties were investigated. Our total energy calculations showed that the sym- N2O4 has lower energy than the other isomers. Therefore, it was selected as the most stable isomer of all. The structural properties of N2O4 isomers determined in this study were in agreement with previous studies. Various possible adsorption geometries were taken into consideration during the adsorption process of the N2O4 molecule onto the fullerene surface. The most stable four structures were obtained without any constraints by performing full structural optimizations. The adsorption energies of these optimized stable structures were calculated as −3.16, −3.35, −3.27, and −3.18 eV for LDA and −2.26, −2.61, −2.51, and −2.27 eV for PBE. These calculated values showed that the adsorption process can be evaluated as a chemisorption. GapHL values were calculated as 1.46, 1.41, 1.21, and 1.28 eV for LDA and 1.45, 0.34, 0.86, and 1.25 eV for PBE. The results obtained in this study regarding the N2O4 adsorption onto the C20 surfaces can be expected to guide future experimental and theoretical studies related to new hybrid semi-conductor material.

Innovative nanocomposite formulations for enhancing biogas and biofertilizers production from anaerobic digestion of organic waste

Herein, the design of nanocomposite (NC) formulations that consist of metal enzyme cofactors, highly conductive carbon materials, DIET activators, to boost AD biogas production from anaerobically incubated cattle manure are investigated and discussed. Three different NC formulations were designed and synthesized: zinc ferrite (ZnFe), ZnFe with 10% carbon nanotubes (ZFCNTs), and zinc ferrite with 10% C76 fullerene (ZFC76). The structure and morphology of the nano-additives were investigated via x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive x-ray (EDX), and transmission electron microscopy (TEM). NCs were supplemented to lab-scale biodigesters containing organic slurry. Biogas production was monitored daily and compared to blank biodigesters for 50 days. The maximum methane enhancement was obtained for ZnFe, which promoted methane production to 185.3%. ZFCNTs and ZFC76 showed a positive impact on the hydraulic retention time and enhanced methane production to 162% and 145.9%, respectively compared to the blank reactors.

Fullerene C76: An Unexplored Superior Electrode Material with Wide Operating Potential Window for High‐Performance Supercapacitors

AbstractCarbon materials have widely been used to enhance the performance of a plethora of supercapacitor electrode materials. In this regard, it is crucial to identify carbon materials that function over a wide pH range while enjoying a wide potential window. Herein, the DFT calculations were used to elucidate the electronic performance of C76 and the C76/electrolyte interface. The electronic investigation revealed the nature of the conductivity and charge storage mechanism of C76 based on the bandgap and quantum capacitance calculations. Also, the electrochemical and electronic properties of fullerene C76 have been extensively investigated over a wide pH range; acidic H2SO4, basic KOH, and neutral Na2SO4. The results showed a promising performance in the three electrolytes. Moreover, C76 electrodes exhibited a potential window of 1.9 V in Na2SO4 electrolyte, resulting in capacitances of 171 F/g and 142 F/g at a scan rate of 1 mV/s in the positive and negative potential windows, respectively. The material showed a pseudocapacitance performance of 65 % in Na2SO4 electrolyte in the positive potential window. We believe higher fullerenes provide a new class of materials for developing versatile supercapacitor devices for efficient energy storage.