Time-Resolved Mass Spectrometric Studies of Fullerenes and Endohedral Fullerenes

Abstract

The energetics and dynamics of C₂ evaporations from fullerene radical cations C_n ^?+ were studied with and without ion trapping techniques. Electron space charge trapping was applied in electron ionization experiments. RF trapping in a Paul type ion source was applied for Laser MPI. Appearance energies, kinetic energy releases and metastable fractions were determined. the experimental data were modeled by finite heat bath theory (FHBT) and by RRKM/QET. Evaporation (binding) energies as well as conventional and intrinsic kinetic shifts were deduced. Our results support the following conclusions: (a) C₆₀ sits on the leading edge of a magic shell, with C₅₈ only slightly less stable and C₆₂ considerably less stable than C₆₀; (b) Dissociative decay is able to compete with radiative decay of C₆₀ ^?+ only at internal energies in excess of 37.6 eV (T_b>2300 K); (c) a Ne endohedral atom has a slightly stabilizing effect on the C₆₀ ^?+ cage whereas La is strongly stabilizing the C₈₂ ^?+ cage; (d) C₂ loss is a true evaporation in the sense of having a loose transition state with no reverse activation energy; (e) the C₂ evaporations are statistical in nature and theories such RRKM/QET and FHBT are in excellent agreement with experimental observations.     

金属氮化物富勒烯的研究现状

内嵌金属氮化物簇富勒烯的发现极大地扩展了内嵌富勒烯家族。内嵌金属氮化物富勒烯是一类将含有金属原子的氮化物(Mx-N,AxM3-x-N)包裹在富勒烯碳笼中的化合物,因其具有独特的分子结构和性质而受到人们广泛的研究和关注。阐述了合成金属氮化物富勒烯的方法,着重介绍了电弧法,探讨了氮源对电弧法合成金属氮化物富勒烯产量的影响,介绍了金属氮化物富勒烯常用的分离提纯方法,最后讨论了金属氮化物富勒烯的结构特点、性质和潜在应用。     

Carbon Clusters Formation by Laser Irradiation of Carbonaceous Solids

Abstract

A laser ablation/Fourier‐transform ion cyclotron resonance mass spectrometry was used to generate fullerenes clusters from targets of carbonaceous material containing carbyne, C₆₀ photopolymer, graphite, diamond, C₆₀ fullerene crystals.     

内嵌放射性金属同位素富勒烯的制备及生物学研究

综述了内嵌放射性金属同位素富勒烯的制备及医用研究现状。内嵌金属富勒烯的制备目前主要采用电弧放电法,但产率还较低;而放射性内嵌金属富勒烯的合成,主要是利用镧系区域的钬、钐和镥等具有合适的中子捕获截面及适当的半衰期的元素首先由电弧法制备,然后在中子的辐照下形成。因中子辐照会破坏碳笼,故放射性内嵌金属富勒烯的产率更低。动物实验是利用BALB/c小鼠和Fischer大鼠进行活体代谢实验,结果表明,放射性钬内嵌金属富勒烯主要分布于骨骼和肝脏,毒性低而靶向性高。放射性内嵌金属富勒烯有望成为新型放射性药物或示踪剂。     

Dependence of Amorphous Formation Ability on Intrinsic Parameters in Dy-Gd-Co-Al Alloys

A series of Dy(Gd)-based bulk amorphous alloy rods were prepared by water-cooled copper mold method. Thermal stability and structure of Dy-Gd-Co-Al alloys were investigated by differential scanning calorimetry and X-ray di-raction,respectively.The results show that the Dy-Gd-Co-Al alloys have good glass-formation ability,and the Dy31Gd25Co20Al24 alloy can be readily cast into full glassy rods up to 5 mm in diameter.The glass-forming ability of multicomponent alloys was greatly dependent on their chemical in...     

Formation of Metallic Nanowires by Laser Ablation in Liquid Helium

Laser ablation of metals in liquid helium results in the formation of metal filaments with diameters on the order of 2?C10 nanometres and of spherical nanoparticles. In superfluid helium these nanowires aggregate into centimeter-sized networks. We study the morphology and the electric conductivity of these large aggregates, as well as extinction spectra and the crystalline structure of the individual nanofragments. We discuss the effect of superfluidity on the mechanisms of coalescence processes at the nanometer and centimeter scales.     

紫外激光特性参数与医用生物学软组织消融应用

100nm～400nm的紫外激光依靠光化学能对物质产生分解作用,这一不产生热能的特性优势正被生命科学应用领域所瞩目.本文通过引用近年来国际国内实验室获得的基础性研究数据,追溯了紫外激光的测量技术及目前临床应用的紫外光的规格由来.     

脉冲激光轰击法连续制备金掺杂的 YBCO杂化材料研究

采用聚焦脉冲激光轰击浸于流动YBCO前体氧化物水溶胶中的金靶，连续制备了金掺杂的YBCO前体氧化物水溶胶，进而煅烧获得金掺杂的YBCO杂化材料．TEM和XRD结果表明金掺杂使YBCO杂化材料粒径和晶化程度变小，能谱扫描测得金掺杂前后YBCO杂化材料中的Y、Ba和Cu相对含量未发现明显偏差，但金只在其中个别区域探测到，表明在煅烧过程中金发生了团聚．     

On the Formation and Stability of Fullerenes

Abstract

Fullerenes (especially the higher ones) degrade to an insoluble material on storage in air. The C _2v(II) isomer of [78]fullerene is completely degraded after storage for 5 months. The extreme instability may account for the variable yields of this isomer obtained by different research groups. Strong heating of KBr discs of these insoluble materials produces CO₂ showing that they are oxygen containing. Given this inherent instability of fullerenes, the question arises as to why they are formed in the first place. It is argued that the formation is not a unique consequence of the need to eliminate dangling bonds produced during carbon vaporisation by the arc-discharge procedure. Rather, fullerene formation is favoured by a higher intramolecular dangling-bond collision frequency (i.e. much higher Arrhenius A-factor) for cage closure compared to the intermolecular collisions that lead to the more stable graphitic sheets.     

On the Size Dependence of Standing Waves in Tubular Fullerenes

Summary

We present an analysis of principal vibrational modes whose propagation creates the standing waves along the lateral surfaces of the elongated fullerenes.

We deduce the recurrence rules determining the possibility of resonances between the skew and vertical modes, as well as the appearance of isolated standing waves with nodes in the elongated fullerenes C_N with N = 50 + 10k, k= 1,2,3….

We discuss briefly the influence of different vibrational spectra on the mechanical stability of C_N-elongated fullerenes, and its impact on the relative rate of their production.

     

On the Formation and Stability of Fullerenes

Fullerenes (especially the higher ones) degrade to an insoluble material on storage in air. The C_2v(II) isomer of [78]fullerene is completely degraded after storage for 5 months. The extreme instability may account for the variable yields of this isomer obtained by different research groups. Strong heating of KBr discs of these insoluble materials produces CO₂ showing that they are oxygen containing. Given this inherent instability of fullerenes, the question arises as to why they are formed in the first place. It is argued that the formation is not a unique consequence of the need to eliminate dangling bonds produced during carbon vaporisation by the arc-discharge procedure. Rather, fullerene formation is favoured by a higher intramolecular dangling-bond collision frequency (i.e. much higher Arrhenius A-factor) for cage closure compared to the intermolecular collisions that lead to the more stable graphitic sheets.     

Superconductivity of Organic Materials: Beyond the Fullerenes

Abstract

We first briefly review the application of the BCS mechanism with electron-phonon interaction to the superconductivity of the A₃C₆₀ compounds. We then explore an extension of this family of compounds by using aromatic cryptands that we consider as “pseudo fullerene molecules”. Preliminary measurements of low field microwave absorption are consistent with superconducting behavior and a Tc ～ 50K.

     

Superconductivity of Organic Materials: Beyond the Fullerenes

We first briefly review the application of the BCS mechanism with electron-phonon interaction to the superconductivity of the A₃C₆₀ compounds. We then explore an extension of this family of compounds by using aromatic cryptands that we consider as “pseudo fullerene molecules”. Preliminary measurements of low field microwave absorption are consistent with superconducting behavior and a Tc ∼ 50K.     

Synthesis of Fullerenes by Ablation Using Pulsed and cw-Nd:YAG Lasers

Macroscopic quantities of fullerenes were synthesized by ablation of a graphite rod heated with a cw-Nd:YAG laser in Ar gas flow. The ablation was carried out by irradiation of fundamental, second, and third harmonic light emitted from a pulsed-Nd:YAG laser. It was necessary to heat the graphite rod up to a higher temperature than 700 °C for producing macroscopic quantities of fullerenes. The amount of ablation, the fullerene yield and the relative fullerene yield increased with increasing temperature of graphite. The fullerpne yields depended on the pressure of Ar buffer gas as well, in which the j ablation plume was formed, and an optimum pressure range was found to be 53-80 kPa. Relatively high yield of C₇₀ was obtained by ablation method under these conditions.     

锂离子电池碳阳极材料的电化学嵌锂行为：嵌入过程,表面层的形成及锂 …

综述了锂离子电池碳阳极材料的电化学嵌锂行为,包括三个主要方面,嵌入过程,表面层的形成及锂的扩散。     

The Formation of Fullerenes from Sonic Velocity Gaseous Carbon

A contact are and adiabatic expansion hybrid reactor has been utilized to provide a controlled cooling process of gaseous carbon species capable of attaining very high velocities. Both vaporization and annealing temperatures and annealing time were found to be impartant for the formation of fullerenes. Immediate rapid quenching of gaseous carbon resulted in the reduction of fullerene yields. However, rapid quenching was demonstrated to improve the fullerene yield by preserving the as-grown fullerenes in the high temperature annealing process.     

The Formation of Fullerenes from Sonic Velocity Gaseous Carbon

Abstract

A contact are and adiabatic expansion hybrid reactor has been utilized to provide a controlled cooling process of gaseous carbon species capable of attaining very high velocities. Both vaporization and annealing temperatures and annealing time were found to be impartant for the formation of fullerenes. Immediate rapid quenching of gaseous carbon resulted in the reduction of fullerene yields. However, rapid quenching was demonstrated to improve the fullerene yield by preserving the as-grown fullerenes in the high temperature annealing process.     

Laser Pyrolysis of Hydrocarbons in Synthesis of Soot Containing Fullerenes

Using a high power CW CO₂ laser, the pyrolysis in a flow reactor of different hydrocarbons/oxidizer mixtures with/without sensitizer lead to soots containing weightable quantities of fullerenes which were identified by FTIR spectroscopy, high performance liquid chromatography (HPLC) and time-of-flight mass spectrometry. The C₆₀ and C₇₀ quantification was done by HPLC. The FTIR spectroscopy of toluene extracts from the soots and of exhaust gases allowed to discuss some aspects concerning the influence of sensitizer (SF₆) addition as well as of the oxidiser (O₂/N₂O) on the fullerene production in laser pyrolysis of benzene-based mixtures.     

Laser Ablation of Doped Polymer Systems

Laser ablation has become a widely recognized tool for materials processing. In the area of polymeric materials, applications of UV lasers for surface modification, microlithography, cutting, and boring have been explored. With the addition of dopants into the bulk, it has become possible to sensitize most known classes of polymers for UV laser ablation at any desired wavelength, including fluoropolymers. Important features of dopant-induced ablation are the reduction of threshold energy fluence required for ablation, and the enhancement of the etching rate by factors higher than ten. In the present review the investigated dopant/polymer systems are summarized and compared. Based on the available information, a general scheme including all relevant pathways is suggested, revealing that in each particular case the dominant mechanism depends on the specific system under study.