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1.
Artigo em Inglês | MEDLINE | ID: mdl-32045508

RESUMO

We achieved concise synthesis of sulfur-enriched graphene for battery applications. The direct treatment of graphene oxide (GO) with commercially available Lawesson's reagent produced sulfur-enriched-reduced GO (S-rGO). Various techniques, such as X-ray photoelectron spectroscopy (XPS), confirmed the occurrence of both sulfur functionalization and GO reduction. We also fabricated a nanohybrid material by using S-rGO with polyoxometalate (POM) as a cathode-active material for a rechargeable battery. Transmission electron microscopy (TEM) revealed that POM clusters were individually immobilized on the S-rGO surface. This battery based on a POM/S-rGO complex exhibited greater cycling stability for the charge-discharge process than a battery with nanohybrid materials positioned between the POM and non-enriched rGO. Our results demonstrate that the use of sulfur-containing groups on a graphene surface can be extended to applications such as the catalysis of electrochemical reactions and electrodes in other battery systems.

2.
Chemistry ; 2020 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-32080906

RESUMO

Owing to their remarkable properties, single-walled carbon nanotube thin film transistors (SWCNT-TFTs) are expected to be used in various flexible electronics applications. To fabricate SWCNT channel layers for TFTs, solution-based film formation on a self-assembled monolayer (SAM) covered with amino groups is commonly used. However, this method uses highly oxidized surfaces, which is not suitable for flexible polymeric substrates. Herein, we report a solution-based SWCNT film fabrication using methoxycarbonyl polyallylamine (Moc-PAA). The NH 2 -teminated surface of the cross-linked Moc-PAA layer enables the formation of highly dense and uniform SWCNT networks on both rigid and flexible substrates. TFTs that use the fabricated SWCNT thin film exhibited excellent performance with small variations. The presented simple method to access SWCNT thin film accelerates the realization of flexible nanoelectronics.

3.
Inorg Chem ; 58(21): 14325-14330, 2019 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-31622085

RESUMO

The photoluminescence of lanthanide ions inside fullerenes is usually very weak due to the quenching effect of the fullerene cage. In the case of Er@C82, the near-infrared emission from the Er3+ ion is completely quenched by the C82 fullerene cage. It remains challenging to turn on the photoluminescence of Er@C82 and other monometallofullerenes. In this work, we adopt a covalent modification strategy to alter the electronic structure of the fullerene cage for sensitizing the near-infrared emission of Er3+ ions in metallofullerenes Er@C2n (2n = 72, 76, and 82). After covalent modification with trifluoromethyl, phenyl, or dichlorophenyl groups, the erbium metallofullerenes exhibit photoluminescence at 1.5 µm, which is the characteristic emission of the Er3+ ion. Particularly, the otherwise nonfluorescent metallofullerene Er@C82 is transformed into fluorescent derivatives by using this strategy. The photoluminescence from the Er3+ ion is ascribed to energy transfer from the fullerene cage to the Er3+ ion. According to theoretical calculations, the sensitization of the Er3+ ion by the fullerene cage is associated with the large HOMO-LUMO gap and the closed-shell electronic structure of the metallofullerene derivatives. This work provides useful guidance for the design and synthesis of new fluorescent metallofullerenes.

4.
J Am Chem Soc ; 140(35): 10955-10959, 2018 09 05.
Artigo em Inglês | MEDLINE | ID: mdl-30125097

RESUMO

DySc2N@C80 is an endohedral metallofullerene showing single-molecule magnet (SMM) behavior. In this work, we encapsulated DySc2N@C80-SMMs into the internal one-dimensional nanospace of single-walled carbon nanotubes (SWCNTs). Using transmission electron microscopy, "peapod" structures were clearly observed. From magnetic field dependent measurements, DySc2N@C80 showed stepwise hysteresis characteristic of SMMs even inside the SWCNTs, and the coercivity increased from 0.5 to 4 kOe. In addition, it showed slow relaxation of the magnetization without an applied external magnetic field. This system is the first example where SMMs have been encapsulated in SWCNTs, and this system could be used in future molecular-spintronics devices.

5.
Nat Commun ; 9(1): 3073, 2018 08 06.
Artigo em Inglês | MEDLINE | ID: mdl-30082836

RESUMO

Endohedral metallofullerenes have been extensively studied since the first experimental observation of La@C60 in a laser-vaporized supersonic beam in 1985. However, most of these studies have focused on metallofullerenes larger than C60 such as (metal)@C82, and there are no reported purified C60-based monomeric metallofullerenes, except for [Li@C60]+(SbCl6)- salt. Pure (metal)@C60 compounds have not been obtained because of their extremely high chemical reactivity. One route to their stabilization is through chemical functionalization. Here we report the isolation, structural determination and electromagnetic properties of functionalized crystalline C60-based metallofullerenes Gd@C60(CF3)5 and La@C60(CF3)5. Synchrotron X-ray single-crystal diffraction reveals that La and Gd atoms are indeed encapsulated in the Ih-C60 fullerene. The HOMO-LUMO gaps of Gd@C60 and La@C60 are significantly widened by an order of magnitude with addition of CF3 groups. Magnetic measurements show the presence of a weak antiferromagnetic coupling in Gd@C60(CF3)3 crystals at low temperatures.

6.
Chem Commun (Camb) ; 54(31): 3823-3826, 2018 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-29445804

RESUMO

1,6-Bis(hydroxymethyl)diamantane spontaneously aligns inside double-walled carbon nanotubes. The encapsulated molecules form a one-dimensional network within the double-walled carbon nanotubes through hydrogen bonding that leads to a highly dense filling as compared to unfunctionalized diamantane. Improving the encapsulation yields of precursors via functionalization is crucial to prepare novel one-dimensional materials.

7.
Chemphyschem ; 19(2): 237-242, 2018 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-29024320

RESUMO

We investigated the energetics and electronic structure of B3 N3 -doped graphene employing density functional theory calculations with the generalized gradient approximation. Our calculations reveal that all of the B3 N3 -doped graphene structures are semiconducting, irrespective of the periodicity of the B3 N3 embedded into the graphene network. This is in contrast to graphene nanomeshes, which are either semiconductors or metals depending on the mesh arrangement. In B3 N3 -doped graphene, the effective masses for both electrons and holes are small. The band gap in the B3 N3 -doped graphene networks and the total energy of the B3 N3 -doped graphene are inversely proportional to the B3 N3 spacing. Furthermore, both properties depend on whether or not the graphene region possesses a Clar structure. In particular, the sheets with a Clar structure exhibit a wider band gap and a slightly lower total energy than those without a Clar structure.

8.
R Soc Open Sci ; 5(9): 181015, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30839731

RESUMO

Our trifluoromethyl functionalization method enables the dissolution and isolation of missing metallofullerenes of Gd@C74(CF3) n . After multi-stage high-performance liquid chromatography purification, Gd@C74(CF3)3 and two regioisomers of Gd@C74(CF3) are isolated. X-ray crystallographic analysis reveals that all of the isolated metallofullerenes react with CF3 groups on pentagons of the D 3 h-symmetry C74 cages. Highest occupied molecular orbital-lowest unoccupied molecular orbital gaps of these trifluoromethylated derivatives, estimated by absorption spectra, are in the range 0.71-1.06 eV, consistent with density functional calculations.

9.
R Soc Open Sci ; 5(9): 180588, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30839750

RESUMO

Using density functional theory approaches, we follow the sequential addition of CF3 functional groups to the surface of the metallic endofullerene species Gd@C60. The presence of gadolinium in the interior of the cage strongly influences the addition sequence. The calculations are able to successfully identify end points in the addition sequence at Gd@C60(CF3) n , n = 3 and two isomers at n = 5, in predictive agreement with experiment. Inverting the algorithm to determine the most labile groups also identifies the correct positively charged Gd@ C 60 ( C F 3 ) 4 + isomer, as confirmed by experimental mass spectra. The importance of surface mobility, notably at later stage addition, is discussed.

10.
Molecules ; 22(5)2017 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-28468241

RESUMO

The purification of endohedral metallofullerenes by high performance liquid chromatography is very time-consuming and expensive. A number of rapid and inexpensive non-chromatographic methods have thus been developed for large-scale purification of metallofullerenes. In this review, we summarize recent advances in non-chromatographic purification methods of metallofullerenes. Lewis acid-based complexation is one of the most efficient and powerful methods for separation of metallofullerenes from empty fullerenes. The first oxidation potential of metallofullerenes is a critical factor that affects the separation efficiency of the Lewis acid-based method. Supramolecular methods are effective for separation of fullerenes and metallofullerenes that are different in size and shape. Chemical/electrochemical reduction and exohedral functionalization are also utilized to separate and purify metallofullerenes on a large scale.


Assuntos
Fulerenos/isolamento & purificação , Cromatografia Líquida de Alta Pressão , Fulerenos/química , Ácidos de Lewis/química , Compostos de Organossilício/química , Oxirredução , Processos Fotoquímicos
11.
J Biomater Sci Polym Ed ; 28(10-12): 1036-1050, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28132586

RESUMO

As novel magnetic resonance imaging (MRI) contrast agent, gadofullerene encapsulated redox nanoparticles (Gd3NPs) were prepared by encapsulation of Gd3N@C80 in the core of core-shell-type polymer micelles composed of original polyamine with a reactive oxygen species (ROS)-scavenging ability. Because Gd3NPs possess biocompatible PEG shell with a smaller size (ca. 50 nm), they had high colloidal stability in a physiological environment, and showed low cytotoxicity. Specific accumulation of Gd3NPs in a tumor was confirmed in tumor-bearing mice after systemic administration. The tumor/muscle (T/M) ratio of the Gd ion reached five at 7.5 h after the administration. T1-weighted MRI signal enhancement of the T/M ratio increased by 8% at 6 h postinjection of Gd3NPs (Gd dose:14.35 µmol/kg). Although Gd3NPs showed a tendency for extended blood circulation, they did not have severe adverse effects, probably due to the confinement of Gd in a hydrophobic fullerene in addition to the ROS-scavenging capacity of these nanoparticles. In sharp contrast, systemic administration of Gd-chelate nanoparticles (GdCNPs) to mice disrupts liver function, increases leukocyte counts, and destroys spleen and skin tissues. Leaking of Gd ions from GdCNPs may cause such adverse effects. Based on these results, we expect that Gd3NPs is high-performance MRI contrast agents for tumor diagnosis.


Assuntos
Meios de Contraste/química , Fulerenos/química , Gadolínio/química , Imagem por Ressonância Magnética/métodos , Nanopartículas , Animais , Cápsulas , Linhagem Celular Tumoral , Meios de Contraste/farmacocinética , Meios de Contraste/toxicidade , Fulerenos/farmacocinética , Fulerenos/toxicidade , Masculino , Camundongos , Oxirredução
12.
Angew Chem Int Ed Engl ; 55(1): 199-202, 2016 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-26530527

RESUMO

D5h-symmetric fullerene C70 (D5h-C70) is one of the most abundant members of the fullerene family. One longstanding mystery in the field of fullerene chemistry is whether D5h-C70 is capable of accommodating a rare-earth metal atom to form an endohedral metallofullerene M@D5h-C70, which would be expected to show novel electronic properties. The molecular structure of La@C70 remains unresolved since its discovery three decades ago because of its extremely high instability under ambient conditions and insolubility in organic solvents. Herein, we report the single-crystal X-ray structure of La@C70(CF3)3, which was obtained through in situ exohedral functionalization by means of trifluoromethylation. The X-ray crystallographic study reveals that La@C70(CF3)3 is the first example of an endohedral rare-earth fullerene based on D5h-C70. The dramatically enhanced stability of La@C70(CF3)3 compared to La@C70 can be ascribed to trifluoromethylation-induced bandgap enlargement.

13.
Angew Chem Int Ed Engl ; 54(37): 10802-6, 2015 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-26268378

RESUMO

A simple method for the synthesis of linear-chain diamond-like nanomaterials, so-called diamantane polymers, is described. This synthetic approach is primarily based on a template reaction of dihalogen-substituted diamantane precursors in the hollow cavities of carbon nanotubes. Under high vacuum and in the presence of Fe nanocatalyst particles, the dehalogenated radical intermediates spontaneously form linear polymer chains within the carbon nanotubes. Transmission electron microscopy reveals the formation of well-aligned linear polymers. We expect that the present template-based approach will enable the synthesis of a diverse range of linear-chain polymers by choosing various precursor molecules. The present technique may offer a new strategy for the design and synthesis of one-dimensional nanomaterials.

14.
ACS Nano ; 9(5): 5034-40, 2015 May 26.
Artigo em Inglês | MEDLINE | ID: mdl-25868574

RESUMO

Nanotemplated growth of graphene nanoribbons (GNRs) inside carbon nanotubes is a promising mean to fabricate ultrathin ribbons with desired side edge configuration. We report the optical properties of the GNRs formed in single-wall carbon nanotubes. When coronene is used as the precursor, extended GNRs are grown via a high-temperature annealing at 700 °C. Their optical responses are probed through the diazonium-based side-wall functionalization, which effectively suppresses the excitonic absorption peaks of the nanotubes without damaging the inner GNRs. Differential absorption spectra clearly show two distinct peaks around 1.5 and 3.4 eV. These peaks are assigned to the optical transitions between the van Hove singularities in the density of state of the GNRs in qualitative agreement with the first-principles calculations. Resonance Raman spectra and transmission electron microscope observations also support the formation of long GNRs.

15.
Angew Chem Int Ed Engl ; 53(12): 3102-6, 2014 Mar 17.
Artigo em Inglês | MEDLINE | ID: mdl-24616170

RESUMO

A new strategy for the non-chromatographic extraction of metallofullerenes from solutions of arc-processed raw soot is based on the size-selective complexation with cycloparaphenylene (CPP). [11]CPP has a high affinity for Mx @C82 (x=1, 2); for example, Gd@C82 can be selectively extracted from a fullerene mixture by the addition of [11]CPP. This approach should open new opportunities in metallofullerene chemistry, including for the bulk extraction of metallofullerenes.


Assuntos
Fulerenos/química , Estrutura Molecular , Estereoisomerismo
16.
Nat Chem ; 5(7): 572-6, 2013 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23787746

RESUMO

Carbon nanotubes (CNTs), tubular molecular entities that consist of sp(2)-hybridized carbon atoms, are currently produced as mixtures that contain tubes of various diameters and different sidewall structures. The electronic and optical properties of CNTs are determined by their diameters and sidewall structures and so a controlled synthesis of uniform-diameter, single-chirality CNTs-a significant chemical challenge-would provide access to pure samples with predictable properties. Here we report a rational bottom-up approach to synthesize structurally uniform CNTs using carbon nanorings (cycloparaphenylenes) as templates and ethanol as the carbon source. The average diameter of the CNTs formed is close to that of the carbon nanorings used, which supports the operation of a 'growth-from-template' mechanism in CNT formation. This bottom-up organic chemistry approach is intrinsically different from other conventional approaches to making CNTs and, if it can be optimized sufficiently, offers a route to the programmable synthesis of structurally uniform CNTs.


Assuntos
Nanotubos de Carbono , Espectrometria de Fluorescência , Espectrofotometria Infravermelho , Análise Espectral Raman , Estereoisomerismo
17.
Acc Chem Res ; 45(8): 1378-89, 2012 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-22587963

RESUMO

Since their discovery in 1991, carbon nanotubes (CNTs) have attracted significant attention because of their remarkable mechanical, electronic, and optical properties. Structural uniformity of the CNT is critically important because the sidewall structures (armchair, zigzag, and chiral) determine many of the significant properties of CNTs. Ideally researchers would synthesize CNTs with a defined target sidewall structure and diameter, but the current synthetic methods, such as arc discharge and chemical vapor deposition, only provide CNTs as the mixtures of various structures. Purification of these mixtures does not allow researchers to isolate a structurally uniform CNT, which is the bottleneck for fundamental studies and advanced applications of these materials. Therefore, the selective and predictable synthesis of structurally uniform CNTs would represent a critical advance in both nanocarbon science and synthetic chemistry. This Account highlights our efforts toward the bottom-up synthesis of structurally uniform carbon nanotubes (CNTs). We envisioned a bottom-up synthesis of structurally uniform CNTs through a controlled growth process from a short carbon nanoring (template) that corresponds to the target structure of CNTs. Our simple retrosynthetic analysis led to the identification of cycloparaphenylenes (CPPs), acene-inserted CPPs, and cyclacenes as the shortest sidewall segments of armchair, chiral, and zigzag CNTs, respectively. With this overall picture in mind, we initiated our synthetic studies of aromatic rings/belts as an initial step toward structurally uniform CNTs in 2005. This research has led to (i) a general strategy for the synthesis of CPPs and related carbon nanorings using cyclohexane derivatives as a benzene-convertible L-shaped unit, (ii) a modular, size-selective, and scalable synthesis of [n]CPPs (a shortest segment of armchair CNTs), (iii) the X-ray crystal structure analysis of CPPs, (iv) the design and synthesis of acene-inserted CPPs as the shortest segment of chiral CNTs, and (v) the first synthesis of cyclo-1,4-naphthylene, a π-extended CPP. We believe this work will serve as important initial steps toward a controlled synthesis of CNTs.


Assuntos
Benzeno/química , Benzeno/síntese química , Técnicas de Química Sintética/métodos , Nanotecnologia/métodos , Nanotubos de Carbono/química , Cristalografia por Raios X , Estereoisomerismo
18.
Org Biomol Chem ; 10(30): 5979-84, 2012 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-22441238

RESUMO

We studied the UV-vis absorption and fluorescence in solution/solid states of [n]cycloparaphenylene ([n]CPP: n = 9, 12, 14, 15, and 16), and conducted theoretical studies to better understand the experimental results. The representative experimental findings include (i) the most intense absorption maxima (λ(abs1)) display remarkably close values (338-339 nm), (ii) the longest-wavelength absorption maxima (λ(abs2)) are blue-shifted with increasing the ring size (395 → 365 nm), (iii) the emission maxima (λ(em)) are blue-shifted with increasing the ring size (494 → 438 nm for longest-wavelength maxima), (iv) the fluorescent quantum yields (Φ(F)) in solution are high (0.73-0.90), (v) the fluorescence lifetimes (τ(s)) of [9]- and [12]CPP are 10.6 and 2.2 ns, respectively, and (vi) the Φ(F) values slightly increase in polymer matrix but significantly decrease in the crystalline state. According to TD-DFT calculations, the longest-wavelength absorption (λ(abs2)) corresponds to a forbidden HOMO → LUMO transition and the most intense absorption (λ(abs1)) corresponds to degenerate HOMO - 1 → LUMO and HOMO → LUMO + 1 transitions with high oscillator strength. The interesting and counterintuitive optical properties of CPPs (constant λ(abs1) and blue shift of λ(abs2)) could be ascribed mainly to the ring-size effect in frontier molecular orbitals (in particular the increase of the HOMO-LUMO gap as the number of benzene rings increases). On the basis of comparative calculations using hypothetical model geometries, we conclude that the unique behavior of HOMO and LUMO of CPPs is due mainly to their lack of a conjugation length dependence in combination with a significant bending effect (particularly to HOMO) and a torsion effect (particularly to LUMO).

19.
Org Lett ; 13(9): 2480-3, 2011 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-21486080

RESUMO

A simple and realistic model for the shortest sidewall segments of chiral single-walled carbon nanotubes (SWNTs) has been designed, and one of the chiral carbon nanorings, cyclo[13]paraphenylene-2,6-naphthylene ([13]CPPN, 1) has been successfully synthesized. DFT calculations reveal that the racemization energy of 1 is 8.4 kcal·mol(-1). In addition, some important energetic values, such as racemization barriers and strain energies, of other chiral carbon nanorings have been systematically estimated for future molecular design.

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