Probe beam deflection combined with cyclic voltammetry studies of C-60-modified electrode film

C-60 films, prepared by solution casting, were studied by means of in situ probe beam deflection (PBD) combined with cyclic voltammetry (CV). PBD is a powerful technique for investigation of phenomena at the electrode/electrolyte interface in acetonitrile with quaternary ammonium and alkali metal salts as supporting electrolytes. In tetra-n-butylammonium (TBA(+)) salt solution, a stable CV can be obtained during the first two reduction/reoxidation waves. On reduction, injection of cations to maintain charge balance and dissolution of small amount of C-60(-) (TEA(+)) and/or C-60(2-) (TBA(+))(2) are detected. During the reoxidation process ejection of cations and injection of anions occur simultaneously, especially for the second reoxidation wave. In the case where TBABr is the supporting electrolyte, the accompanied behavior is more complicated than in TBABF(4), TBAClO(4), and TBAPF(6) solutions. A small pair of prewaves in CV are proposed due to oxidation/reduction of C-60 domains but not dissolution/redeposition of C-60 film. Extending the potential scan range to the third reduction wave, no apparent corresponding reoxidation wave is related to the third reduction wave, the electroactivity of the film disappears rapidly and dissolution of C-60 film is observed. In tetraethylammonium (TEA(+)) and NAClO(4) solutions, the electrochemistry of the C-60 films is unstable, and potential scans lead to dissolution of flaking of the film.

C-60 trianion-mediated electrocatalysis and amperometric sensing of hydrogen peroxide

Heterogeneous electrocatalytic reduction of hydrogen peroxide (H2O2) by C-60 is reported for the first time. C-60 is embedded in tetra octyl ammonium bromide (TOAB) film and is characterized by scanning electron microscopy and cyclic voltammetry. Electrocatalytic studies show that the trianion of C-60 mediates the electrocatalytic reduction of H2O2 in aqueous solution containing 0.1 M KCl. Application of such film modified electrode as an amperometric sensor for H2O2 determination is also examined.

Ambipolar permeable metal-base transistor based on NPB/C-60 heterojunction

In this paper, we report the fabrication of permeable metal-base organic transistors based on N,N'-diphenyl-N,N'-bis(1-naphthylphenyl)-1,1'-biphenyl-4,4'-diamine (NPB)/C-60 heterojunction as both emitter and collector. By applying different polarities of voltage bias to the collector and the base, and input current to the emitter, the ambipolar behavior can be observed. The device demonstrates excellent common-base characteristics both in P-type and N-type modes with common-base current gains of 0.998 and 0.999, respectively.

Effective enhancement of peroxydisulfate electrochemiluminescence on C-60/DDAB films

Effective enhancement of electrochermluminescence (ECL) of peroxydisulfate on a C-60/didodecyldimethyl ammonium bromide (C-60/DDAB) film coated glassy carbon electrode (GCE) surface is reported in this paper. The C60/DDAB film gave lower cathodic current in the presence of peroxydisulfate than that from a bare GCE. To our surprise, electrochemiluminescent intensity from peroxydisulfate reduction was effectively enhanced on the C60/DDAB film, which was 50 times and 250 times higher than those from a DDAB film coated and bare GCE, respectively. Moreover, the ECL onset potential on the C60/DDAB film was about -0.9 V, which positively shifted 200 mV compared with that from the bare GCE. Dissolved oxygen and the applied potential also affected the electrochemiluminescent intensity. The presence of oxygen decreased the intensity, and the intensity reached maximum at the applied potential of -1.7 V. The unique property will greatly enrich ECL studies and applications based on fullerenes.

Interfacial supramolecular self-assembled monolayers of C-60 by thiolated beta-cyclodextrin on gold surfaces via monoanionic C-60

The supramolecular self-assembled monolayers (SAMs) of C-60 by thiolated beta-cyclodextrin (CD) on gold surfaces were constructed for the first time using C-60 monoanion. The results indicate that monoanionic C-60 plays a crucial role in the formation of the C-60-containing self-assembled monolayers. The generation of C-60 monoanion and the formation process of C-60 SAMs were monitored in-situ by UV-visible and near-IR spectroscopy. The resulting C-60 SAMs were fully characterized by spectroscopic ellipsometry (SE), cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), and water contact angle measurements. After the immobilization of C-60 by the SAMs of thiolated beta-CD, the film thickness increased by approximately 1 nm from 0.8 to 1.8 nm as determined by SE, demonstrating the formation of the supramolecular self-assembled monolayers of thiolated beta-CD/C-60. The new C-60 SAMs exhibited one quasi-reversible redox couple at half wave potential of -0.57 V vs SCE in aqueous solution containing 0.1 M KCl. The surface coverage of C-60 on the gold surfaces was estimated to be 1.1 x 10(-10) mol cm(-2). The XPS showed the assembly of C-60 over the thiolated beta-CD SAMs.

Anomalous temperature dependence of photoluminescence from a-C : H film deposited by energetic hydrocarbon ion beam

The temperature dependence of photoluminescence (PL) from a-C:H film deposited by CH3+ ion beam has been performed and an anomalous behavior has been reported. A transition temperature at which the PL intensity, peak position and full width at the half maximum change sharply was observed. It is proposed that different structure units. at least three, are responsible for such behavior. Above the transition point. increasing temperature will lead to the dominance of non-radiative recombination process, which quenches the PL overall and preferentially the red part, Possible emission mechanisms have been discussed. (C) 2002 Elsevier Science Ltd. All rights reserved.

INVESTIGATION OF C-60 SINGLE-CRYSTAL BY X-RAY-METHODS

C-60 Single crystals grown by a single-temperature-gradient technique were characterized by synchrotron radiation white beam x-ray topography and x-ray double crystal diffraction with Cu K-alpha 1 radiation on conventional x-ray source. The results show that the crystal is rather well crystallized, The x-ray topographies give an evidence of dendritic growth mechanism of C-60 Single crystal, and x-ray double crystal diffraction rocking curve shows that there are mosaic structural defects in the sample. A phase transition st 249+/-1.5% K from a simple cubic to a face centered cubic structure is confirmed by in situ observation of synchrotron radiation white beam x-ray topography with the temperature varing from 230 to 295 K.

重离子~(12)C对~(60)Coγ射线诱发人染色体畸变效应的比较研究

目的　重离子和高剂量率6 0 Coγ射线照射离体人血建立染色体畸变的剂量 效应曲线 ;比较重离子1 2 C照射与6 0 Coγ射线照射诱发染色体畸变的相对生物效能。方法　重离子1 2 C和6 0 Coγ射线照射离体人血 ,吸收剂量率为 3Gy min ,吸收剂量为 1 0～ 8 0Gy。主要记录染色体型畸变的非稳定性畸变 ,对双着丝粒体和着丝粒环做曲线拟合 ,并检验回归系数的显著性和曲线的拟合度。结果　重离子1 2 C和6 0 Coγ射线照射离体血诱发的染色体畸变 (双 +环 ) ,在 0～ 8Gy范围内 ,呈良好的剂量 效应关系。1 2 C离子诱发染色体畸变的RBE值是不恒定的 ,它随吸收剂量增加而减少 ,在 0 3～ 8 0Gy范围内 ,RBE值 (Dγ Dc)从 2 6 2到 1 0 0 ,平均 1 5 8。结论　1 2 C离子对6 0 Coγ射线照射诱发染色体畸变 ,在照射剂量较低时 ,有较高的生物效应。

Kinetic energies of C-n(+) (n <= 58) fragment ions produced by nanosecond laser impact on C-60

Laser-induced fragmentation of C-60 has been studied using a time-of-flight mass spectrometric technique. The average kinetic energies of fragment ions C-n(+) (n <= 58) have been extracted from the measured full width at half maximum (FWHM) of ion beam profiles. The primary formation mechanism of small fragment ion C-n(+) (n < 30) is assumed to be a two-step fragmentation process: C60 sequential decay to unstable C-30(+) ion and the binary fission of C-30(+). Considering a second photo absorption process in the later part of laser pulse duration, good agreement is achieved between experiment and theoretical description of photoion formation. (C) 2009 Elsevier B. V. All rights reserved.