Design and analysis of sandwiched fullerene-graphene composites using molecular dynamics simulations

Computational design of a novel carbon based hybrid material that is composed of fullerene units covalently sandwiched between parallel graphene sheets is presented. In this regard, atomistic models for the proposed novel material structure are generated via a systematic approach by employing different fullerene types (i.e. C₁₈₀, C₃₂₀, C₅₄₀ and C₇₂₀) as sandwich cores. Then, thermodynamic stability of the atomistic structures is checked by monitoring free energy profiles and junctional bond configurations which are obtained through classical molecular dynamics (MD) simulations. Thermodynamic feasibility of all atomistic specimens with different fullerene types is suggested by the energy profiles, because total configuration energies for all systems are minimized and remained stable over a long period of time. Furthermore, mechanical behavior of the nano-sandwiched material system is investigated by performing compression tests via MD simulations and basic deformation mechanisms underlying the compressive response are determined. By detailed examination, it is shown that proposed nano-sandwiched material can be identified as quasi-foam material due to comparable energy absorbing characteristics. Furthermore, regarding the effect of fullerene size on the compressive response, it is found that for a given stress level, specimens with larger fullerenes exhibit higher energy absorbing capacity.     

Numerical characterisation of fullerene based polymer nanocomposites considering interface effects

In this investigation, the effective mechanical properties of fullerene nanocomposites considering interface effects were characterised. Load transfer in nanocomposite materials is achieved through the fullerene/matrix interface. Thus, to determine nanocomposite mechanical properties, the interface behaviour must be determined. A single fullerene and the surrounding polymer matrix are modelled. Two cases of perfect bonding and an elastic interface are considered. Two models are suggested for elastic interface. The first elastic interface model consists of a thin layer of an elastic material surrounding the fullerene. In the second elastic interface model, a series of spring elements are used as the fullerene/matrix interface. The results of numerical models indicate the importance of adequate interface bonding for a more effective strengthening of polymer matrix by fullerene. Also, Young’s modulus prediction for fullerene in epoxy matrix is compared to experimental data investigated by Rafiee et al. (2011), and good agreement is observed.     

Computer simulation study of fullerene translocation through lipid membranes

Recent toxicology studies suggest that nanosized aggregates of fullerene molecules can enter cells and alter their functions, and also cross the blood-brain barrier. However, the mechanisms by which fullerenes penetrate and disrupt cell membranes are still poorly understood. Here we use computer simulations to explore the translocation of fullerene clusters through a model lipid membrane and the effect of high fullerene concentrations on membrane properties. The fullerene molecules rapidly aggregate in water but disaggregate after entering the membrane interior. The permeation of a solid-like fullerene aggregate into the lipid bilayer is thermodynamically favoured and occurs on the microsecond timescale. High concentrations of fullerene induce changes in the structural and elastic properties of the lipid bilayer, but these are not large enough to mechanically damage the membrane. Our results suggest that mechanical damage is an unlikely mechanism for membrane disruption and fullerene toxicity.     

Modelling of C(2) addition route to the formation of C(60)

To understand the phenomenon of fullerene growth during its synthesis, an attempt is made to model a minimum energy growth route using a semi-empirical quantum mechanics code. C(2) addition leading to C(60) was modelled and three main routes, i.e.?cyclic ring growth, pentagon and fullerene road, were studied. The growth starts with linear chains and, at n = 10, ring structures begins to dominate. The rings continue to grow and, at some point n>30, they transform into close-cage fullerenes and the growth is shown to progress by the fullerene road until C(60) is formed. The computer simulations predict a transition from a C(38) ring to fullerene. Other growth mechanisms could also occur in the energetic environment commonly encountered in fullerene synthesis, but our purpose was to identify a minimal energy route which is the most probable structure. Our results also indicate that, at n = 20, the corannulene structure is energetically more stable than the corresponding fullerene and graphene sheet, however a ring structure has lower energy among all the structures up to n≤40. Additionally, we have also proved that the fullerene road is energetically more favoured than the pentagon road. The overall growth leading to cage closure for n = 60 may not occur by a single route but by a combination of more than one route.     

碳及内嵌金属原子富勒稀分子的压缩力学特性

采用分子动力学(MD)与量子力学(QM)相结合的方法,模拟了Cn(n=20、60、80、180)富勒稀分子,以及M@C60(M=Na、Fe、Al)内嵌金属原子富勒稀分子的对径压缩过程,获得了各种富勒稀分子的系统能量-变形曲线、载荷-变形曲线、最大承受载荷、失效应变以及压缩刚度等压缩力学性能数据.根据模拟的结果,分析了具有不同幻数n、不同内嵌金属原子的富勒稀分子压缩力学特性的差异.研究表明,碳富勒稀分子具有出色的压缩力学性能;幻数n较大的富勒稀分子的最大承受载荷和压缩刚度较大,但失效应变较小;与未填充碳富勒稀分子相比,内嵌金属原子富勒稀分子具有更好的承载能力.     

Improved wear properties of magnesium matrix composite with the addition of fullerene using semi powder metallurgy

The present study aims to fabricate fullerene (C60) reinforced magnesium matrix composite via semi powder metallurgy in hot press system under high purity argon atmosphere. Improvement of wear resistance of pure magnesium with the addition of fullerene is also aimed with this study. Hardness and wear tests at room temperature were performed to investigate the mechanical effect of fullerene nanoparticles. Microstructures of fabricated composites were characterized using Scanning Electron Microscope (SEM). Results clearly show that hardness performance was improved up to 0.5 wt. % fullerene addition directly. A uniform distribution was also achieved according to the mapping and line EDX analysis for the lower content of fullerene. Agglomeration of fullerene was observed for 1 wt. % reinforced composite. Wear performances of pure magnesium were also improved when harder fullerene reinforcements incorporated into the matrix. Abrasion and oxidation were main wear mechanism for unreinforced and fullerene reinforced composites. Enhancement of hardness and wear performances might be attributed to the high specific surface area of fullerene and achievement of uniform distribution of reinforcement in magnesium matrix.     

Investigation of fullerene embedded silicon surfaces with scanning probe microscopy

This study examines the intramolecular structures of individual fullerene molecules on a Si(111)-7 x 7 surface using an ultra-high vacuum scanning tunneling microscope. This study also discusses possible configurations of fullerene molecules with related orientations and electronic states of fullerene. A self-assembled layer of fullerene on a Si(111) surface is produced using special annealing treatments. The resulting electronic states and band gap energy can be estimated from I-V curves. Finally the field emission parameters, such as turn-on field and field enhancement factor beta, are determined using a traditional detecting system.     

Studies on Protein–[60]Fullerene Interactions: The Lysozyme–[60]Fullerene Model System

Abstract

A lysozyme–[60]fullerene adduct was synthesized and isolated for the first time. This adduct was water‐soluble and showed strong interaction between lysozyme and [60]fullerene and was characterized by UV‐VIS and fluorescence energy transfer technique. Keeping possible biomedical applications of [60]fullerene in view, the protein–[60]fullerene interactions were studied taking lysozyme as a model protein.     

Mechanical,flow and electrical properties of thermoplastic polyurethane/fullerene composites: Effect of surface modification of fullerene

Thermoplastic polyurethane (TPU) composites with fullerene loadings varying from 0.5 to 2 weight% were prepared by melt-mixing method. Nitric acid oxidation and silanization were applied to fullerene surface to improve interfacial interactions with TPU matrix. The influence of surface modifications of fullerene on mechanical, melt flow and electrical properties of TPU based composites were investigated. Incorporation of fullerene leads to nearly twofold increase in tensile strength and Young's modulus of the composites in addition to enhancing the flexibility. The best results are obtained in nitric acid and silane modified fullerene containing composites at the lowest concentration (0.5%). Higher MFI values were observed for composites loaded with surface treated fullerenes compared to pristine fullerene because of their better dispersion in TPU. Electrical properties of TPU also improved by the addition of surface modified fullerene particles. Surface oxidation and silanization gave rise to dispersion homogeneity which may be the reason of both tensile strength and strain improvements at the same time.     

Preparation and dielectric properties of fullerene-doped polyarylene ether nitrile film

In order to obtain polymer films with low dielectric constant (≤2.0) and enhanced mechanical strength, fullerene-doped polyarylene ether nitrile (PEN) film was designed and prepared according to the following step. At first, fullerene and PEN were dissolved in toluene and N-methyl pyrrolidone, respectively, and the solutions were mixed together. The films were prepared by solution casting/solvent evaporation method on glass sheet. The morphology and thermal analysis of the films were characterized by visual & SEM observation and DSC & TGA test, respectively. The mechanical properties and dielectric properties of the films were also measured. The results showed that the dispersion of fullerene was largely dependent on the evaporation methods of the solvents. The glass transition temperature (Tg) and thermal decomposition temperature (Td) of PEN films were improved with the addition of fullerene. The dielectric constant sharply decreased from 4.0 to about 2.0 with the addition of fullerene. At the same time, the mechanical properties were improved, which might be caused by the physical entanglement of PEN chains with fullerenes. The lowest ε value (1.75 at 1 MHz) and the highest tensile strength (142.2 Mpa) were simultaneously obtained in samples containing 3 wt% fullerenes, which indicated it’s the optimal content of fullerene.     

Glucose/Fe-doped C70 fullerene hybrid biosensor: theoretical study

Abstract

The interaction between glucose molecule and C70 fullerene (pristine and Fe-doped) was investigated with the aid of density functional theory. Our results provide useful information that uncover the chemical and biological activities of C70 when interact with glucose molecule. To mimic real situations, all possible configurations of glucose with respect to fullerene were investigated under both vacuum and distilled water mediums. As expected, no significant change in the calculated energy gaps for all pristine configurations regardless the simulated medium, which indicates that the interaction between glucose molecule and pristine Fullerene is weak physisorption. However, doping fullerene with Fe atom significantly reduced the energy gap for all configurations of the complex which in turn offers an advantage over pristine fullerene for measuring glucose in real situations such as blood.     

Thermally assisted tunnelling in ambipolar field-effect transistors based on fullerene peapod bundles

We report the first detailed studies of the electrical transport behaviour of C(70) fullerene peapod bundles at various temperatures from 400?K down to 4?K. With electrical breakdown, we have prepared ambipolar (i.e.?both p-?and n-type) field-effect transistors (FETs) using fullerene peapod bundles with high levels of performance. This paper focuses on the role of the Schottky barrier and the thermal activation energy in the transport behaviour of fullerene bundles. The temperature dependence of our measurements reveals that transport is dominated by thermally assisted tunnelling in fullerene bundles at low temperature.     

Production and Characterization of (Al, Fe)-C (Graphite or Fullerene) Composites Prepared by Mechanical Alloying

(Al, Fe)-C_graphite and (Al, Fe)-C_fullerene composites have been prepared by mechanical alloying using ball milling of powders. Consolidation has been achieved by a spark plasma sintering technique (SPS). Results of XRD and TEM indicate that pure fullerene withstands milling. SEM results show homogeneous powders after milling but with different morphologies depending on the specific system. Milling produces a fine mixture of Al or Fe and graphite or fullerene. SPS produces a dense material with a nanocrystalline structure. The sintered samples have a metallic matrix (Al or Fe) with a fine dispersion of AI₄C₃ in the case of Al-C_{( graphiteorfullerene)}, Fe₃,C in the case of Fe-C_(graphite), and fullerene in the case of Fe-C _(fullerene), Hardness measurements show that higher values are obtained in the Al-C_(fullerene), and Fe-C_{(graphite )} specimens.     

Mechanical milling of fullerene with carbide forming elements

Mechanical alloying of Ti, V, Cr, Mo and W with fullerene (C₆₀(C₇₀)) and graphite reveals that fullerene is more reactive than graphite. The formation heat of carbide is the driving force for reaction in the mechanical alloying process. Higher heat of formation results in the direct formation of carbide in Ti-C systems, and the formation of carbide in V-C systems during the subsequent heating of milled powder. In the systemsc with lower carbide heat of formation, a mixture of metal with carbon is obtained by ball milling. No carbide was obtained even after heating the milled powders up to 973 K. Small amount of fullerene remained when milled with Mo and W for 10 hours.     

Lanthanide metals adsorbed in an open-cage Fullerene: first-principles calculations

In this paper, the properties of a 12-membered-ring open-cage fullerene, which encapsulate La, Ce, Pr, Nd, Pm, Sm, Eu or Gd, as a guest atom, were calculated using first-principle calculations. Calculations show that La etc. lanthanide metal atoms can be stably adsorbed on the openings of the fullerenes. The average adsorption energy is about -3.65 eV in which Pr and Nd have relatively large adsorption energy with -4.75 eV and -4.63 eV, respectively. The Gd is stably adsorbed on the side wall near bottom of the fullerene with adsorption energy of -3.05 eV. The PDOS of adsorbed lanthanides were analyzed, respectively. Magnetic property of adsorbed lanthanides was also discussed. From the calculation, it is proved that most of the adsorbed lanthanides keep good magnetic property. Finally, vertical ionization potential and vertical electron affinity of the complex compounds were researched. The results show that the possibility of donating electrons of the 12-membered-ring open-cage fullerene is significantly affected by the endohedral lanthanide metals. From our calculations, it is believed that the complex compounds could be promising candidates for medicine-carrier.     

High‐Performance Organic Bulk‐Heterojunction Solar Cells Based on Multiple‐Donor or Multiple‐Acceptor Components

Organic solar cells (OSCs) based on bulk heterojunction structures are promising candidates for next‐generation solar cells. However, the narrow absorption bandwidth of organic semiconductors is a critical issue resulting in insufficient usage of the energy from the solar spectrum, and as a result, it hinders performance. Devices based on multiple‐donor or multiple‐acceptor components with complementary absorption spectra provide a solution to address this issue. OSCs based on multiple‐donor or multiple‐acceptor systems have achieved power conversion efficiencies over 12%. Moreover, the introduction of an additional component can further facilitate charge transfer and reduce charge recombination through cascade energy structure and optimized morphology. This progress report provides an overview of the recent progress in OSCs based on multiple‐donor (polymer/polymer, polymer/dye, and polymer/small molecule) or multiple‐acceptor (fullerene/fullerene, fullerene/nonfullerene, and nonfullerene/nonfullerene) components.     

Detection of negative fullerene conformers

Negative fullerene metastable negative conformers have been detected using electron transfer neutral atom scattering. The anions have been produced through alkali–fullerene collision process, in an energy range well above the ion-pair formation threshold, but still low enough where only the negative parent ion is formed. The interpretation of the parent ion band structure, in time-of-flight spectra, points to the formation of different fullerene conformers, which are favoured by the strong polarization of the cluster anion due to the positive alkali projectile ion. An electric effect operating at nanoscales enables the experimental detection of spheroidal metastable conformers.     

Charge-associated effects of fullerene derivatives on microbial structural integrity and central metabolism

The effects of four types of fullerene compounds (C60, C60-OH, C60-COOH, C60-NH2) were examined on two model microorganisms (Escherichia coli W3110 and Shewanella oneidensis MR-1). Positively charged C60-NH2 at concentrations as low as 10 mg/L inhibited growth and reduced substrate uptake for both microorganisms. Scanning electron microscopy (SEM) revealed damage to cellular structures. Neutrally charged C60 and C60-OH had mild negative effects on S. oneidensis MR-1, whereas the negatively charged C60-COOH did not affect either microorganism's growth. The effect of fullerene compounds on global metabolism was further investigated using [3-13C]L-lactate isotopic labeling, which tracks perturbations to metabolic reaction rates in bacteria by examining the change in the isotopic labeling pattern in the resulting metabolites (often amino acids).1-3 The 13C isotopomer analysis from all fullerene-exposed cultures revealed no significant differences in isotopomer distributions from unstressed cells. This result indicates that microbial central metabolism is robust to environmental stress inflicted by fullerene nanoparticles. In addition, although C60-NH2 compounds caused mechanical stress on the cell wall or membrane, both S. oneidensis MR-1 and E. coli W3110 can efficiently alleviate such stress by cell aggregation and precipitation of the toxic nanoparticles. The results presented here favor the hypothesis that fullerenes cause more membrane stress 4-6 than perturbation to energy metabolism.7.     

Synthesis, Photophysical and Photovoltaic Properties of New [60]Fullerene Pyrrolidine Derivatives

Two new [60]fullerene pyrrolidine derivatives 2 and 3 were synthesized and characterized by ¹H NMR, ¹³C NMR and MS. Their photophysical processes have been investigated by using laser flash photolysis. The experiments show quenching of oligomer singlet excited state and the evidence of the fullerene singlet excited emission. And the intramolecular of electron transfer and also energy transfer of 2 and 3 occurred and the triplet excited state of fullerene moiety in 2 and 3 have different lifetime due to their different structures. A photovoltaic device using compound 2 as the only photoactive material has also been investigated which showed the energy conversion efficiency is 0.011%.     

Efficient Organic Solar Cells with Non‐Fullerene Acceptors

Fullerene‐free OSCs employing n‐type small molecules or polymers as the acceptors have recently experienced a rapid rise with efficiencies exceeding 12%. Owing to the good optoelectronic and morphological tunabilities, non‐fullerene acceptors exhibit great potential for realizing high‐performance and practical OSCs. In this Review, recent exciting progress made in developing highly efficient non‐fullerene acceptors is summarized, mainly correlating factors like absorption, energy loss and morphology of new materials to their correspondent photovoltaic performance.