Production of endohedral <Superscript>133</Superscript>Xe-higher fullerenes by ion implantation

Endohedral ¹³³Xe-higher fullerenes (¹³³Xe@C₇₆ and ¹³³Xe@C₈₄) were produced by implantation of ¹³³Xe ions using an isotope separator. A high performance liquid chromatography (HPLC) analysis showed that the peak of endohedral ¹³³Xe-higher fullerenes shifted backward from that of empty fullerenes, suggesting a possibility of the separation of endohedral ¹³³Xe-higher fullerenes from empty fullerenes. The yields of endohedral ¹³³Xe-fullerenes were in the order of ¹³³Xe@C₇₆<¹³³Xe@C₈₄<¹³³Xe@C₆₀<¹³³Xe@C₇₀.     

Conversion of endohedral <Superscript>133</Superscript>Xe-fullerene to endohedral <Superscript>133</Superscript>Xe-fullerenol to be used in nuclear medicine

Summary Hydrophilic endohedral ¹³³Xe-fullerenols, [¹³³Xe@C₆₀(OH)_xand ¹³³Xe@C₇₀(OH)_x], were synthesized from hydrophobic endohedral ¹³³Xe-fullerenes. The yield of endohedral ¹³³Xe-fullerenols extracted in water was about 40% and 23% for C₆₀and C₇₀, respectively. The products stored in 0.9% NaCl solution at 20 °C were stable enough to be used in nuclear medicine.     

Low concentration spectroscopic standards by ion implantation

Summary Standards for spark-source mass spectrometric use were prepared by ion implantation. Implanted thin metal foils were rolled up to produce electrodes suitable for the measurements. Results for some matrices and implanted ions have been compiled.

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Herstellung spektroskopischer Vergleichsproben mit niedriger Konzentration durch Ionenimplantation

Zusammenfassung Vergleichsproben für die Funken-Massenspektrometrie wurden durch Ionenimplantation hergestellt. Die vorher mit den gewünschten Elementen implantierten dünnen Metallschichten wurden zusammengerollt, um für die Funkenionenquelle geeignete Elektroden zu erhalten. Ergebnisse für einige Matrices und implantierte Ionen werden gegeben.

     

Structure and properties of polymers modified by ion implantation

Thin films of oriented polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE) and polyamide (PA6) were modified by the implantation of 150 keV Sb⁺ ions to the fluences 10¹²–10¹⁵ cm⁻². The Sb depth profiles were determined by a standard Rutherford back-scattering technique and the range parameters were found to differ from the theoretical TRIM estimate. The thickness of the ion beam modified surface layer is about 150 nm for all polymers examined. Production of conjugate double bonds and polymer surface oxidation were proved by means of i.r. and u.v. spectroscopies. Surface polarity, obtained by goniometric measurements, is an increasing function of the implanted dose with only the exception of PA6 where a polarity decrease is observed. The measured temperature dependence of the sheet resistivity for PE, PP and PA6 do not correspond to the well known variable range hopping mechanism.     

Modifications of polypropylene surface properties by He+ ion implantation

A polypropylene (PP) modified by ethylene–propylene rubber (EPR) was treated in vacuo by α particles (with an energy of 400 keV) with fluences that varied from 10¹¹ to 10¹⁶ He⁺ cm^?2. Samples were investigated with attenuated total reflection Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, contact‐angle measurements, differential scanning calorimetry, swelling, nanoindentation, and friction techniques. After treatment, new chemical groups (carbonyl and vinyl bonds) appeared at the PP/EPR surface. These chemical modifications led to changes in the surface free energy of PP/EPR. Irradiation also modified the PP/EPR structure because crosslinking occurred after treatment for fluences above or equal to 5 × 10¹⁴ He⁺ cm^?2. Moreover, the PP melting temperature and enthalpy were greatly decreased for fluences above or equal to 10¹⁴ He⁺ cm^?2. The surface mechanical properties were also changed after treatment. Indeed, the friction coefficient decreased, whereas the hardness and Young's modulus drastically increased, after irradiation at higher fluences. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1183–1191, 2003     

Molecular ion implantation in silicon

¹⁵N₂ ⁺ molecular ions were implanted with 10keV (j=10 A/cm²) under high vacuum conditions close to room temperature in 100 silicon (c-Si) to study the¹³N depth distributions, particularly the dependence of peak concentration and dose on the ion fluence. The analysis were performed by the resonant nuclear reaction¹⁵N(p, )¹²C(NRA). A maximum peak concentration of 65 at.% was measured. Thin stoichiometric silicon nitride layers with a thickness of approx. 20 nm (15 at.% nitrogen at the specimen surface) were produced by this low-energy implantation of¹⁵N₂ ⁺ ions with an ion fluence of 1.5·10¹⁷ ions/cm². NRA analysis of 38 keV¹⁵N₂ ⁺ and 19keV¹⁵N⁺ ion implantations were performed to compare the¹⁵N depth distributions. No significant changes in the depth distributions are measured, that means, the molecular¹⁵N₂ ⁺ ions are already disintegrated passing the very first atomic layers of the sample during implantation. Non-Rutherford RBS with⁴He⁺ ions and 3.45 MeV was performed in order to confirm the results obtained by NRA.Dedicated to Professor Dr. rer.nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

Control of endothelial cell adhesion to polymer surface by ion implantation

The bio‐compatibility of ion implanted polymers has been studied by means of in vitro attachment measurements of bovine aorta endothelial cells. The specimens used were polystyrene (PS), polyethylene (PE), polypropylene (PP) and expanded polytetrafluoroethylene (ePTFE). He⁺ and Ne⁺ ion implantation were performed at an energy of 150 keV with fluences between 1 × 10 ¹³ to 1 × 10 ¹⁷ ions/cm ² at room temperature. Wettability was estimated by means of a sessile drop method. The chemical and physical structures of ion implanted polymers were investigated by contact angle measurements, atomic force microscopy and X‐ray photoelectron spectroscopic analysis in relation to cell attachment behavior. The strength of cell attachment on ion implanted specimens at static and under flow conditions was also measured. Ion implanted PP and ePTFE were found to exhibit remarkably higher adhesion and spreading of endothelial cells than non‐implanted specimens. In contrast to these findings, ion implanted PS and PE only demonstrated a little improvement of cell adhesion in this assay. Copyright © 2001 John Wiley & Sons, Ltd.     

Synthesis of lead chalcogenide nanocrystals by sequential ion implantation in silica

Lead chalcogenide (PbS, PbSe, and PbTe) nanocrystals were synthesized by sequential implantation of Pb and one of the chalcogen species into pure silica. The implantation energy and fluence were chosen so that the implantation profiles practically overlap at a depth approximately 150 nm with a maximum concentration of about 0.3 atom %. Annealing for 1-8 h at 850-900 degrees C triggers nanocrystal growth, which is monitored by high-resolution (HRTEM) and conventional transmission electron microscopy (TEM), secondary-ion mass spectrometry (SIMS), and Rutherford backscattering spectrometry (RBS). Striking differences are found in the depth distributions and microstructures of the resulting nanocrystals. We show that the differing chemical interactions of Pb and chalcogens (between each other and with silica) play a crucial role in chalcogenide nucleation and growth. Using available information on chalcogen redox states in silicate glass, we propose a nonclassical nucleation and growth mechanism consistent with our experimental results. The complex chemistry involved at the microscopic level is shown to impair control over the nanocrystal size distribution. Finally, PbS nanocrystal-doped silica is shown to emit intense photoluminescence (PL) in the 1.5-2 microm wavelength range, an effect that we relate to the above nucleation and growth scheme.     

X-ray imaging during plasma-source ion implantation

Plasma source ion implantation (PSII) is a technique for modifying stafaces that places the object to he modified directly into a plasma and then negatively pulse biases the object so as to implant positive ions. If the voltage is high enough, X-rays can he generated by electrons that are also accelerated by the pulse. This work describes techniques for imaging and characterizing the X-rays A pinhole camera was used to image the X-rays being emitted as electrons collided with surfaces in the chamber. The images show that X-rays are generated at the chamber walls and near the target. The time dependence of these X-rays during each pulse was examined using a PIN diode X-ray detector. Then, using another X-ray sensor and pulseheight analyzer, the spectra of the emitted X-rays was determined. The object is to relate the X-ray intensity and spectrum to the temporal and spatial values of the implantation dose so that it may he used as a process monitor and a control sensor.     

Synthesis of endohedral metallofullerene glycoconjugates by carbene addition

Endohedral metallofullerene glycoconjugates were synthesized under mild conditions by carbene addition using appropriate glycosylidene-derived diazirine with La(2)@I(h)-C(80). NMR spectroscopic studies revealed that the glycoconjugate consists of two diastereomers of [6,6]-open mono-adducts. The electronic properties were characterized using Vis/NIR absorption spectroscopy and electrochemical measurements. This study demonstrates that glycosylidene carbene is useful to incorporate carbohydrate moieties onto endohedral metallofullerene surfaces.     

Modification of diamond single crystals by chromium ion implantation with sacrificial layers

Single-crystal diamond surfaces were implanted with chromium ions. Ion energies chosen were 120 and 180 keV. Ion doses of 1x10(17) cm(-2) were applied at a substrate temperature of 750 degrees C. Reduced lattice damage could be obtained by deposition of a titanium sacrificial layer with a thickness of 10 and 50 nm before implantation. Depth profiles of the elemental binding states were taken by photoelectron spectroscopy. The effect of the sacrificial layer thickness on diamond lattice damage was investigated by infrared spectroscopy.     

Conductive and optical properties of PPV modified by N+ ion implantation

In this article, a soluble poly[2‐methoxy‐5‐(3′‐methyl)butoxy]‐p‐phenylene vinylene (MMB‐PPV) was synthesized by dehydrochlorination reaction and the MMB‐PPV film was implanted by nitrogen ions (N⁺) with the ion dose and energy in the range of 3.8 × 10¹⁵ to 9.6 × 10¹⁶ ions/cm² and 15–35 keV, respectively. The surface conductivity, optical absorption, optical band gap (E_g) of modified MMB‐PPV film were studied, and the third‐order nonlinear optical susceptibility (χ⁽³⁾) as well as its environmental stability of modified MMB‐PPV film were also measured by degenerate four‐wave mixing system. The results showed that the surface conductivity of MMB‐PPV film was up to 3.2 × 10^?2 S when ion implantation was performed with the energy of 35 keV at an ion dose of 9.6 × 10¹⁶ ions/cm², which was seven order of magnitude higher than that of the pristine film. UV‐Vis absorption spectra demonstrated that the optical absorption of MMB‐PPV film was enhanced gradually in the visible region followed by a red shift of optical absorption threshold and the E_g value was reduced from 2.12 eV to 1.59 eV with the increase of ion dose and energy. The maximum χ⁽³⁾ value of 2.45 × 10^?8 esu for modified MMB‐PPV film was obtained with the ion energy of 20 keV at an ion dose of 3.8 × 10¹⁶ ions/cm², which was almost 33 times larger than that for pristine film. In comparison to the reduction of 17% in the χ⁽³⁾ value of pristine MMB‐PPV film, the maximum χ⁽³⁾ value of 2.45 × 10^?8 esu for modified MMB‐PPV film decreased by over 5.3% when they had been exposed under the same ambient conditions for 90 days. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2072–2077, 2010     

内嵌富勒烯的研究进展

内嵌富勒烯由于其结构新颖以及独特而优异的性质在国际上引起持续而广泛的关注,成为近年来的研究热点之一.目前已经研究发现的内嵌富勒烯多达近百种,从惰性气体到碱土金属再到稀土元素都已被成功地嵌入到不同尺寸的碳笼中.其中金属离子或含金属的离子簇内嵌入富勒烯碳笼形成的内嵌金属富勒烯,以其种类丰富、结构多样成为内嵌富勒烯的主要研究对象.本文就近年来研究报道的种类繁多的内嵌富勒烯按其内嵌物类型进行归纳阐述,为今后开发更多新型的内嵌富勒烯提供一定的参考.     

Surface cavities produced by high‐dose nitrogen ion implantation into silicon

Nitrogen ion implantation (24 keV, 4.6 × 10¹⁷ cm^?2) into (100) a p‐type silicon wafer material and a subsequent electron beam annealing at 1100 °C for 15 s under high vacuum conditions leads to the formation of an uneven surface in the implanted region caused by nitrogen bubbles beneath the surface. Annealing at 1200 °C for 300 s results in surface cavities with a mean diameter of 350 nm and a surface coverage of 3–4% and an average depth of ～60 nm. Nuclear reaction analysis reveals that the nitrogen concentration in the as‐implanted state exceeds 57 at%, the value of stoichiometric Si₃N₄. Annealing at 1100 °C for 15 s slightly reduces the nitrogen peak concentration, whereas annealing at 1200 °C for 300 s induces a significant alteration to the shape of the nitrogen depth profile coupled with the lowering of the concentration close to the stoichiometry of Si₃N₄. The results present a new method of producing sub‐micrometre cavities embedded in a thin silicon nitride film on wafer silicon which may lead to novel micro‐electronic and biotechnology applications. Copyright © 2007 John Wiley & Sons, Ltd.     

Quantum-chemical study of endohedral fullerenes

State-of-the-art in quantum-chemical research on endohedral fullerenes is considered. Separate chapters are devoted to complexes with noble gases, main group elements, and methals and their nitrides. The structures and the mechanisms of formation and decomposition of these compound sare highlighted. Applicability of various quantum-chemical methods for endohedral fullerene complexes is discussed. Problems associated with the use of the ROHF and UHF methods are revealed. The DFT method with hybrid functionals and effective core potentials for heavy atoms is shown to hold the greatest promise.     

Enantioselective synthesis of endohedral metallofullerenes

Endohedral metallofullerenes are promising materials in biomedical and material sciences. In particular, they are of interest as agents for magnetic resonance imaging (MRI), photovoltaic devices, and semimetallic components. The synthesis of chiral endofullerenes represents one step further in the potential use of these carbon allotropes; however, this step has not been addressed so far. In this regard, enantiopure endofullerenes are expected to open new avenues in fields in which chirality is a key issue. Here, the synthesis and characterization of the first chiral endohedral metallofullerenes, namely, chiral bis-adducts of La@C(72), are reported. Eight optically active isomers were obtained by enantioselective 1,3-dipolar cycloaddition of a N-metalated azomethine ylide onto a non-isolated-pentagon rule metallofullerene derivative, La@C(72)(C(6)H(3)Cl(2)), catalyzed by a copper chiral complex. The chiral bis-adducts of La@C(72), isolated by nonchiral HPLC, showed optical purities as high as 98% as revealed by the remarkable positive or negative Cotton effects observed in the circular dichroic spectra.