Chromatographic Assessment of Organic Compounds Using Carbon Nanotubes: The Relationship between Affinity and Dispersibility.

The affinity between carbon nanotubes (CNTs) and organic compounds is of substantial importance since it strongly relates to the dispersibility of CNTs in those compounds. Several affinity evaluation methods have been developed so far, and the concept of the Hansen solubility parameter is a representative method widely used in the field of nanocarbon materials. Here, we demonstrate that CNT-loaded silica columns can effectively assess the affinity of organic compounds for CNT surface by exploiting the chromatographic retention time as a criterion. Obtained trends of the affinity of organic compounds for CNT were compared to those based on Hansen solubility parameter distance values. Most organic compounds showed similar trends, but one exceptional compound was observed. Simple CNT dispersion tests were conducted with these organic compounds to demonstrate the advantage of the chromatographic assessment. Further, we conducted comparison experiments using a pyrene-functionalized column and other CNT-loaded columns to elucidate the characteristics of each CNT column. The chromatographic approaches using CNT columns would be beneficial for realizing CNT suspensions with improved CNT dispersibility.

Enhanced reactivity of Li+@C60 toward thermal [2 + 2] cycloaddition by encapsulated Li+ Lewis acid.

Lithium ion-endohedral fullerene (Li+@C60), a member of the burgeoning family of ion-endohedral fullerenes, holds substantial promise for diverse applications owing to its distinctive ionic properties. Despite the high demand for precise property tuning through chemical modification, there have been only a few reports detailing synthetic protocols for the derivatization of this novel material. In this study, we report the synthesis of Li+@C60 derivatives via the thermal [2 + 2] cycloaddition reaction of styrene derivatives, achieving significantly higher yields of monofunctionalized Li+@C60 compared to previously reported reactions. Furthermore, by combining experimental and theoretical approaches, we clarified the range of applicable substrates for the thermal [2 + 2] cycloaddition of Li+@C60, highlighting the expanded scope of this straightforward and selective functionalization method.

Enhancing the Thermal Conductivity of CNT/AlN/Silicone Rubber Composites by Using CNTs Directly Grown on AlN to Achieve a Reduced Filler Filling Ratio.

Achieving the thermal conductivity required for efficient heat management in semiconductors and other devices requires the integration of thermally conductive ceramic fillers at concentrations of 60 vol% or higher. However, an increased filler content often negatively affects the mechanical properties of the composite matrix, limiting its practical applicability. To address this issue, in this paper, we present a new strategy to reduce the required ceramic filler content: the use of a thermally conductive ceramic composite filler with carbon nanotubes (CNTs) grown on aluminum nitride (AlN). We combined catalyst coating technology with vacuum filtration to ensure that the catalyst was uniformly applied to micrometer-sized AlN particles, followed by the efficient and uniform synthesis of CNTs using a water-assisted process in a vertical furnace. By carefully controlling the number of vacuum filtration cycles and the growth time of the CNTs, we achieved precise control over the number and length of the CNT layers, thereby adjusting the properties of the composite to the intended specifications. When AlN/CNT hybrid fillers are incorporated into silicone rubber, while maintaining the mechanical properties of rubber, the thermal diffusivity achieved at reduced filler levels exceeds that of composites using AlN-only or simultaneous AlN and CNTs formulations. This demonstrates the critical influence of CNTs on AlN surfaces. Our study represents a significant advancement in the design of thermally conductive materials, with potential implications for a wide range of applications.

Visualization of deformation-induced changes in carbon nanotube networks in rubber composites using lock-in thermography.

In this study, we used the lock-in thermography technique (LIT) to successfully visualize the single-walled carbon nanotube (CNT) networks during the tensile deformation of CNT/fluoro-rubber (FKM) composites. The LIT images revealed that the CNT network modes in CNT/FKM during strain-loading and unloading can be classified into four sites: (i) disconnection, (ii) recovery after disconnection, (iii) undestroyable, and (iv) no network. Quantitative analysis of the heat intensity of the LIT also indicated that the change in resistance during strain-loading and unloading plays a role in the balance of disconnection and reconstruction of the conductive network. We demonstrated the ability of LIT to effectively visualize and quantify the network state of the composite under deformation, and the LIT results were found to be strongly correlated with the composite properties. These results highlighted the potential of LIT as a valuable tool for composite characterization and material design.

Commercial Wet-Spun Singlewall and Dry-Spun Multiwall Carbon Nanotube Fiber Surface O-Functionalization by Ozone Treatment.

In this work, we demonstrate controlled introduction of O-functional groups on commercial carbon nanotube fibers (CNTFs) with different nanotube morphologies obtained by dry- and wet-spinning by treatment with gaseous ozone (O3(g)). Our test samples were (1) wet-spun fibers of smalldiameter (1-2 nm) singlewall (SW)-CNTs and (2) dry-spun fibers containing large-diameter (20 nm) multiwall (MW)-CNTs. Our results indicate that SW-CNTFs undergo oxygenation to a higher extent than MW-CNTFs due to the higher reactivity of SW-CNTs with a larger curvature strain. Oxygenation resulting from O3 exposure was evidenced as increase in surface O atomic% (at% by X-ray photoelectron spectroscopy, XPS) and as reductions in G/D (by Raman spectroscopy) as well as electrical conductivities due to changes in nanotube graphitic structure. By XPS, we identified the emergence of various types of O-functionalities on the fiber surfaces. After long duration O3 exposure (>300 s for SW-CNTFs and >600 s for MW-CNTFs), both sp² C═O (carbonyl) and sp³ C-O moieties (ether/hydroxy) were observed on fiber surfaces. Whereas, only sp³ C-O (ether/hydroxy) components were observed after shorter exposure times. O3 treatment led to only changes in surface chemistry, while the fiber morphology, microstructure and dimensions remained unaltered. We believe the surface chemistry controllability demonstrated here on commercial fibers spun by different methods containing nanotubes of different structures is of significance in aiding the practical application development of CNTFs.

Structure of [60]fullerene with a mobile lithium cation inside.

The structure of crystalline [60]fullerene with a lithium cation inside (Li+@C60) was determined by synchrotron radiation X-ray diffraction measurements to understand the electrostatic and thermal properties of the encapsulated Li+ cation. Although the C60 cages show severe orientation disorder in [Li+@C60](TFPB-)·C4H10O and [Li+@C60](TFSI-)·CH2Cl2, the Li+ cations are rather ordered at specific positions by electrostatic interactions with coordinated anions outside the C60 cage. The Li+@C60 molecules in [Li+@C60](ClO4-) with a rock-salt-type cubic structure are fully disordered with almost uniform spherical shell charge densities even at 100 K by octahedral coordination of ClO4- tetrahedra and show no orientation ordering, unlike [Li+@C60](PF6-) and pristine C60. Single-bonded (Li+@C60-)2 dimers in [Li+@C60-](NiOEP)⋅CH2Cl2 are thermally stable even at 400 K and form Li+-C bonds which are shorter than Li+-C bonds in [Li+@C60](PF6-) and suppress the rotational motion of the Li+ cations.

Negative Pressure Wound Therapy Followed by Basic Fibroblast Growth Factor Spray as a Recovery Technique in Partial Necrosis of Distally Based Sural Flap for Calcaneal Osteomyelitis: A Case Report.

The distally based sural flap is regarded as the first choice for reconstruction in the distal part of the lower leg because the flap is easy to raise, reliable in its blood supply, and prone to only a few complications. Limited data have investigated the details of treatment in cases of failure of distally based sural flaps. We report a case of calcaneal osteomyelitis in which a successful outcome was finally obtained with a partially necrosed, distally based sural flap using negative pressure wound therapy with basic fibroblast growth factor spray. The 2-year follow-up examination was uneventful. Moreover, the patient was able to walk freely with an ankle-foot orthosis in her house. This technique can be considered as a useful and effective option to recover unfavorable results of distally based sural flaps.

The Impact of the Polymer Chain Length on the Catalytic Activity of Poly(N-vinyl-2-pyrrolidone)-supported Gold Nanoclusters.

Poly(N-vinyl-2-pyrrolidone) (PVP) of varying molecular weight (M w = 40-360 kDa) were employed to stabilize gold nanoclusters of varying size. The resulting Au:PVP clusters were subsequently used as catalysts for a kinetic study on the sized-dependent aerobic oxidation of 1-indanol, which was monitored by time-resolved in situ infrared spectroscopy. The obtained results suggest that the catalytic behaviour is intimately correlated to the size of the clusters, which in turn depends on the molecular weight of the PVPs. The highest catalytic activity was observed for clusters with a core size of ~7 nm, and the size of the cluster should increase with the molecular weight of the polymer in order to maintain optimal catalytic activity. Studies on the electronic and colloid structure of these clusters revealed that the negative charge density on the cluster surface also strongly depends on the molecular weight of the stabilizing polymers.

Potential Suppressive Effects of Two C60 Fullerene Derivatives on Acquired Immunity.

The therapeutic effects of fullerene derivatives on many models of inflammatory disease have been demonstrated. The anti-inflammatory mechanisms of these nanoparticles remain to be elucidated, though their beneficial roles in allergy and autoimmune diseases suggest their suppressive potential in acquired immunity. Here, we evaluated the effects of C60 pyrrolidine tris-acid (C60-P) and polyhydroxylated fullerene (C60(OH)36) on the acquired immune response in vitro and in vivo. In vitro, both C60 derivatives had dose-dependent suppressive effects on T cell receptor-mediated activation of T cells and antibody production by B cells under anti-CD40/IL-4 stimulation, similar to the actions of the antioxidant N-acetylcysteine. In addition, C60-P suppressed ovalbumin-specific antibody production and ovalbumin-specific T cell responses in vivo, although T cell-independent antibodies responses were not affected by C60-P. Together, our data suggest that fullerene derivatives can suppress acquired immune responses that require T cells.

Regioselective addition of Grignard reagents to tosylazafulleroid and derivatization to 1,2-disubstituted [60]fullerene.

Grignard reagents (RMgBr: R = Et, p-tolyl) selectively attacked the ß-position of the bridgehead double bond of tosylazafulleroid through interaction of Mg with the S[double bond, length as m-dash]O group. The following [5,6] ring closure and C-N bond scission led to aryl/alkyl aminylfullerenes with 1,2-configuration. Tolyl-substituted aminylfullerene was further converted into 1,4-di(p-tolyl)fullerene on treatment in acidic toluene.

Electrochemical reduction of cationic Li+@C60 to neutral Li+@C60˙-: isolation and characterisation of endohedral [60]fulleride.

Lithium-encapsulated [60]fullerene Li@C60, namely, lithium-ion-encapsulated [60]fullerene radical anion Li+@C60˙-, was synthesised by electrochemical reduction of lithium-ion-encapsulated [60]fullerene trifluoromethanesulfonylimide salt [Li+@C60](TFSI-). The product was fully characterised by UV-vis-NIR absorption and ESR spectroscopy as well as single-crystal X-ray analysis for the co-crystal with nickel octaethylporphyrin. In solution Li@C60 exists as a monomer form dominantly, while in the crystal state it forms a dimer (Li@C60-Li@C60) through coupling of the C60 radical anion cage. These structural features were supported by DFT calculations at the M06-2X/6-31G(d) level of theory.

Hydroxylated fullerene: a potential antiinflammatory and antioxidant agent for preventing mouse preterm birth.

OBJECTIVE: Intrauterine infection such as by Escherichia coli and Ureaplasma spp induce placental inflammation and are one of the leading causes of preterm birth. Here we evaluated hydroxylated fullerene (C60[OH]44) for its in vitro antiinflammatory and antioxidant effects against host cellular responses to the ureaplasma toll-like receptor 2 (TLR2) ligand, UPM-1. In addition, we investigated the preventative effects of C60(OH)44 in vivo in a mouse preterm birth model that used UPM-1. STUDY DESIGN: TLR2-overexpressing cell lines and the primary cultures of mouse peritoneal macrophages were pretreated with C60(OH)44. After UPM-1 addition to the cell lines, the activation of the nuclear factor kappa-light chain-enhancer of activated B cells (NF-kappaB) signaling cascade and the production of reactive oxygen species were monitored. The levels of expression of inflammatory cytokines of interleukin (IL)-6, IL-1ß, tumor necrosis factor (TNF)-α, and the production of reactive oxygen species were quantified after stimulation with UPM-1. The in vivo preventative effects of C60(OH)44 on mice preterm birth were evaluated by analyzing the preterm birth rates and fetal survival rates in the preterm birth mouse model with placental histological analyses. RESULTS: Pretreatment with C60(OH)44 significantly suppressed UPM-1-induced NF-kappaB activation and reactive oxygen species production in TLR2-overexpressing cell lines. In the primary culture of mouse peritoneal macrophages, UPM-1-induced production of reactive oxygen species and the expression of inflammatory cytokines such as IL-6, IL-1ß, and TNF-α were significantly reduced by pretreatment with C60(OH)44. In the UPM-1-induced preterm birth mouse model, the preterm birth rate decreased from 72.7% to 18.2% after an injection of C60(OH)44. Placental examinations of the group injected with C60(OH)44 reduced the damage of the spongiotrophoblast layer and reduced infiltration of neutrophils. CONCLUSION: C60(OH)44 was effective as a preventative agent of preterm birth in mice.

Hetero Bis-Addition of Spiro-Acetalized or Cyclohexanone Ring to 58π Fullerene Impacts Solubility and Mobility Balance in Polymer Solar Cells.

Fullerene bis-adducts are increasingly being studied to gain a high open circuit voltage (Voc) in bulk heterojunction organic photovoltaics (OPVs). We designed and synthesized homo and hetero bis-adduct [60]fullerenes by combining fused cyclohexanone or a five-membered spiro-acetalized unit (SAF5) with 1,2-dihydromethano (CH2), indene, or [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). These new eight 56π fullerenes showed a rational rise of the lowest unoccupied molecular orbital (LUMO). We perform a systematic study on the electrochemical property, solubility, morphology, and space-charge-limited current (SCLC) mobility. The best power conversion efficiency (PCE) of 4.43% (average, 4.36%) with the Voc of 0.80 V was obtained for poly(3-hexylthiophene) (P3HT) blended with SAF5/indene hetero bis-adduct, which is a marked advancement in PCE compared to the 0.9% of SAF5 monoadduct. More importantly, we elucidate an important role of mobility balance between hole and electron that correlates with the device PCEs. Besides, an empirical equation to extrapolate the solubilities of hetero bis-adducts is proposed on the basis of those of counter monoadducts. Our work offers a guide to mitigate barriers for exploring a large number of hetero bis-adduct fullerenes for efficient OPVs.

Oxidative deamination of azafulleroids into C60 by peracids.

Oxidation of azafulleroids with peracids regenerated C60 depending on the N-substituents. Alkyl-substituted azafulleroids preferred the oxidation of nitrogen to afford N-oxides as possible intermediates for C60 in moderate yields. Phenyl- and tosyl-substituted azafulleroids rather allowed the oxidation at the carbon cage. Theoretical calculations predicted the order of reactivity of azafulleroids as well as the relative N/C nucleophilicity.

Stereochemistry of spiro-acetalized [60]fullerenes: how the exo and endo stereoisomers influence organic solar cell performance.

Exploiting bis-addition products of fullerenes is a rational way to improve the efficiency of bulk heterojunction-type organic photovoltaic cells (OPV); however, this design inherently produces regio- and stereoisomers that may impair the ultimate performance and fabrication reproducibility. Here, we report unprecedented exo and endo stereoisomers of the spiro-acetalized [60]fullerene monoadduct with methyl- or phenyl-substituted 1,3-dioxane (SAF6). Although there is no chiral carbon in either the reagent or the fullerene, equatorial (eq) rather than axial (ax) isomers are selectively produced at an exo-eq:endo-eq ratio of approximately 1:1 and can be easily separated using silica gel column chromatography. Nuclear Overhauser effect measurements identified the conformations of the straight exo isomer and bent endo isomer. We discuss the origin of stereoselectivity, the anomeric effect, intermolecular ordering in the film state, and the performance of poly(3-hexylthiophene):substituted SAF6 OPV devices. Despite their identical optical and electrochemical properties, their solubilities and space-charge limited current mobilities are largely influenced by the stereoisomers, which leads to variation in the OPV efficiency. This study emphasizes the importance of fullerene stereochemistry for understanding the relationship between stereochemical structures and device output.

Synthesis and photoluminescent properties of geometrically hindered cis-tris(diphenylaminofluorene) as precursors to light-emitting devices.

A novel highly luminescent tris-fluorenyl ring-interconnected chromophore tris(DPAF-C9) was synthesized using a C3 symmetrical triaminobenzene core as the synthon. This structure bears three light-harvesting 2-diphenylamino-9,9-dialkylfluorenyl (DPAF) ring moieties with each attached by two branched 3',5',5'-trimethylhexyl (C9) arms. A major stereoisomer was chromatographically isolated and characterized to possess a 3D structural configuration of cis-conformer in a cup-form. Molecular calculation at B3LYP/6-31G* level revealed the unexpected stability of this cis-cup-conformer of tris(DPAF-C9) better than that of the stereoisomer in a propeller-form and the trans-conformer. The structural geometry is proposed to be capable of minimizing the aggregation related self-quenching effect in the condensed phase. Fluorescence emission wavelength of tris(DPAF-C9) was found to be in a close range to that of PVK that led to its potential uses as the secondary blue hole-transporting material for enhancing the device property toward the modulation of PLED performance.

Dramatic mechanistic change in acid-catalyzed arylation of azafulleroids depending on their ambident N/C basicity: formation of cyclopentene centered pentakisadduct.

Azafulleroid, amino-bridged [5,6]-open fullerene, has the ambident N/C basicity of the incorporated enamine moiety. Acid-catalyzed arylation of N-substituted azafulleroids proceeded via two types of initial N/C protonation to perform monoarylation or 1,4-bisarylation for the N-alkyl substituents and shuttlecock-type pentakisarylation for the N-phenyl substituent. The dramatic product change was explained by considering the possible mechanism as well as the DFT computational results.

Kinetic study of the Diels-Alder reaction of Li⁺@C60 with cyclohexadiene: greatly increased reaction rate by encapsulated Li⁺.

We studied the kinetics of the Diels-Alder reaction of Li(+)-encapsulated [60]fullerene with 1,3-cyclohexadiene and characterized the obtained product, [Li(+)@C60(C6H8)](PF6(-)). Compared with empty C60, Li(+)@C60 reacted 2400-fold faster at 303 K, a rate enhancement that corresponds to lowering the activation energy by 24.2 kJ mol(-1). The enhanced Diels-Alder reaction rate was well explained by DFT calculation at the M06-2X/6-31G(d) level of theory considering the reactant complex with dispersion corrections. The calculated activation energies for empty C60 and Li(+)@C60 (65.2 and 43.6 kJ mol(-1), respectively) agreed fairly well with the experimentally obtained values (67.4 and 44.0 kJ mol(-1), respectively). According to the calculation, the lowering of the transition state energy by Li(+) encapsulation was associated with stabilization of the reactant complex (by 14.1 kJ mol(-1)) and the [4 + 2] product (by 5.9 kJ mol(-1)) through favorable frontier molecular orbital interactions. The encapsulated Li(+) ion catalyzed the Diels-Alder reaction by lowering the LUMO of Li(+)@C60. This is the first detailed report on the kinetics of a Diels-Alder reaction catalyzed by an encapsulated Lewis acid catalyst rather than one coordinated to a heteroatom in the dienophile.

First synthesis and aggregation behaviour of periconjugated triazoliumfullerene.

Triazoliumfullerene was first prepared by the [3+2] cycloaddition of in situ generated 1,3-diaza-2-azoniaallene with fullerene and was characterized by the dispersed positive charge over the fullerene sphere associated with periconjugation. This new type of amphiphilic fullerene tended to form vesicles and crystalline aggregates after the casting of THF or MeOH solutions.

Ionic conductivity of [Li+@C60](PF6(-)) in organic solvents and its electrochemical reduction to Li+@C60(·-).

The ionic conductivity of [Li(+)@C60](PF6(-)) was measured in o-dichlorobenzene, and found to be higher than that of TBA(+)PF6(-). Electrochemical reduction of [Li(+)@C60](PF6(-)) without any supporting electrolyte gave the monovalent radical anion Li(+)@C60˙(-), as confirmed by the characteristic ESR signal and NIR absorption band.