Effect of Addition Groups on the Redox Properties of Fullerenes

采用循环伏安法和微分脉冲伏安法对比地研究了包括五种Ｃ６０的衍生物及四种Ｃ７０的衍生物的电化学性质．结果表明，推电子基团的引入使得富勒烯的氧化还原电位负移，这种负移的程度与加成基团的性质、个数和富勒烯的性质有关．对于Ｃ６０和Ｃ７０的单加成产物，负移的范围是０．０８～０．２０Ｖ．而对于Ｃ６０的双加成和三加成产物负移的范围分别为０．３０～０．３２Ｖ和０．５３～０．５８Ｖ．同时由于电位的负移大部分衍生物在低于＋１．５Ｖ（ｖｓ．ＳＣＥ）观察到了氧化峰，而Ｃ６０和Ｃ７０本身的氧化高达＋１．７Ｖ（ｖｓ．ＳＣＥ）．特别是对于Ｃ７０的双加成产物在＋０．４５Ｖ（ｖｓ．ＳＣＥ）出现了一个不可逆氧化峰，但是，对于同样加成基团的Ｃ６０双加成产物的氧化却在＋０．９０Ｖ（ｖｓ．ＳＣＥ），说明由于推电子基团的双加成引入，明显改变了Ｃ７０的电负性．Electrochemical properties of fullerene derivatives, including five C60 derivatives and four C70 derivatives, were studied systematically and comparatively by cyclic voltammetry and differential pulse wave voltammetry. The addition of the electrondonating groups on the fullerenes caused negative shift of the redox potentials of the fullerenes. The extent of the negative shift depends on the number and properties of the addition groups, and on the nature of the fullerenes. 0.08～0.20 V negative shift was observed for C60 and C70 monoadducts, 0.30～0.32 V for bisadduct and 0.53～0.58 V for triadduct of C60. Meanwhile, the oxidation waves of most of these derivatives appeared on their cyclic voltammograms. Particularly, an irreversible oxidation of the C70 bisadduct took place at +0.45 V (vs. SCE), while that of C60 bisadduct was at +0.90 V (vs. SCE), indicating that the electronegativity of C70 was greatly reduced by the bisaddition of the electrondonating groups.作者联系地址：中国科学院化学研究所Author's Address: Insti. of Chem., The Chinese Academy of Sinences, Beijing 10008

Significantly accelerated direct electron-transfer kinetics of hemoglobin in a C-60-MWCNT nanocomposite film

The direct electrochemistry of hemoglobin (Hb) was studied in a novel all-carbon nanocomposite film of C-60-MWCNT (MWCNT = multiple-walled carbon nanotube) and compared with that in bare MWCNT film. The heterogeneous electron-transfer rate constant k(s) of Hb/C-60-MWCNT was determined to be 0.39 s(-1), which is more than one order of magnitude greater than that of Hb/MWCNT (0.03 s(-1)). The significantly accelerated electron-transfer kinetics are attributed to the mediator role played by C-60, which is finely dispersed on the MWCNT surfaces. The excellent stability of Hb/C-60-MWCNT was established and its potential application towards the electrocatalytic reduction of O-2 was demonstrated

Studies of Metallofullerene (Dy@C82) Embedded in a DDAB Film in Aqueous Solution

The electrochemical behavior of metallofullerene (Dy@C-82) in didodecyldimethylammonium bromide (DDAB) films deposited on glassy carbon, quartz crystal microbalance (QCM) gold crystals, and indium tin oxide (ITO) electrodes in aqueous solution was investigated in detail. Four pairs of reversible redox peaks were observed, and for the first time, these peaks were characterized by vis/NIR spectroscopy. Different from previous fullerene/cationic lipid modified electrodes, one oxidation and three reduction processes were observed. The stability of Dy@C-82 and its ions in the film toward air was detected by measuring its cyclic voltammogram after holding the potentials for 10 s, followed by introducing 10 mu L of air to the solution. Dy@C-82 and its first three anions are stable toward air and water, while some chemical reactions take place when the third anion is further reduced in the film. Dy@C-82(+) is less stable than Dy@C-82(-) toward water and air. The electrochemical processes were measured in different electrolytes, which showed pronounced anionic dependence on either its cation or anions. The electrochemical processes were also monitored using electrochemical quartz crystal microbalance (EQCM), and from the result a possible electron-transfer mechanism of a Dy@C-82/DDAB electrode in aqueous solution was presented. It showed that the anions of Dy@C-82 were bound to the DDA(+) cation in the film, while the anions of electrolyte diffused into the film to compensate the positive charges when a cation of Dy@C-82 was generated.Hong Kong Univ Sci & Technol, Dept Chem, Kowloon, Hong Kong, Peoples R China

Synthesis and characterization of a grapevine nanostructure consisting of single-walled carbon nanotubes with covalently attached [60]fullerene balls

A grapevine nanostructure based on single-walled carbon nanotubes (SWNTs) covalently functionalized with [60]fullerene (C-60) has been synthesized and characterized in detail. Investigations into the ball-on-tube carbon nanostructure by ESR spectroscopy indicate a tendency for ground-state electron transfer from the SWNT to the C-60 moieties. The cyclic-voltammetric response of the nanostructure film exhibits reversible multiple-step electrochemical reactions of the dispersed C-60, which are strikingly similar to those of the C60 derivatives in solution, but with consistent negative shifts in the redox potential. This results from the covalent linkage of C-60 to the surfaces of the SWNTs in the form of monomers and manifests the electronic interaction between the C-60 and SWNT moieties

Growing vertical ZnO nanorod arrays within graphite: efficient isolation of large size and high quality single-layer graphene

We report a unique strategy for efficiently exfoliating large size and high quality single-layer graphene directly from graphite into DMF dispersions by growing ZnO nanorod arrays between the graphene layers in graphite

Electrochemical route to the preparation of highly dispersed composites of ZnO/carbon nanotubes with significantly enhanced electrochemiluminescence from ZnO

ZnO nanostructures were electrochemically deposited on the surfaces of carbon nanotubes (CNTs) supported on a Zn foil cathode, leading to the facile formation of ZnO/CNT composites with uniform mixing, high dispersion and high-quality interfaces. The electrochemical deposition method circumvents the need for bridging molecules to bring together the two phases and has the key advantage of controllability. By increasing the deposition time, the individual CNTs were first fully covered with ZnO and then the morphology of the deposited ZnO nanostructures was gradually changed from spherical nanoparticles to lily-like nanoflowers. The lily-like structures of ZnO/CNT nanocomposites showed enhanced electrochemiluminescence (ECL). Significantly, the ECL intensity of the lily-like structure of ZnO/CNT nanocomposites was almost an order of magnitude larger than that of pure ZnO nanoflowers, and the ECL starting voltage shifts positively from -1.06 to -0.41 V. These have been attributed to the presence of CNTs which decrease the barriers of ZnO reduction during the ECL process and the special structure of ZnO on the surface of CNTs as well. This work has demonstrated a new strategy to directly coat CNTs with oxides, probably many other inorganic materials, with tunable coverage and nanostructure. Furthermore, the significantly enhanced ECL of ZnO by interfacing with the CNTs highlights the importance and potential utility of such nanostructuring in the development of optoelectronic and biomedical devices

Electrochemical Preparation of N-Doped Cobalt Oxide Nanoparticles with High Electrocatalytic Activity for the Oxygen-Reduction Reaction

Nitrogen-doped CoO (N-CoO) nanoparticles with high electrocatalytic activity for the oxygen-reduction reaction (ORR) were fabricated by electrochemical reduction of CoCl2 in acetonitrile solution at cathodic potentials. The initially generated, highly reactive nitrogen-doped Co nanoparticles were readily oxidized to N-CoO nanoparticles in air. In contrast to their N-free counterparts (CoO or Co3O4), N-CoO nanoparticles with a N content of about 4.6% exhibit remarkable ORR electrocatalytic activity, stability, and immunity to methanol crossover in an alkaline medium. The CoNx active sites in the CoO nanoparticles are held responsible for the high ORR activity. This work opens a new path for the preparation of nitrogen-doped transition metal oxide nanomaterials, which are promising electrocatalysts for fuel cells

Highly Selective and Sensitive Detection of Dopamine in the Presence of Excessive Ascorbic Acid Using Electrodes Modified with C-60-Functionalized Multiwalled Carbon Nanotube Films

Electrochemical detection of dopamine (DA) in the presence of a large excess of ascorbic acid (AA) was investigated with a novel all-carbon nanocomposite film of C-60-MWCNTs (C-60-functionalized multi-walled carbon nanotubes) using a bare MWCNTs film as control. Although both films can selectively detect DA from AA by separating their oxidation potentials, the C-60-MWCNTs film shows special selectivity and good sensitivity for detecting DA. On one hand, the C-60-MWCNTs composite film shows a higher activity for DA oxidation with enhanced peak current. On the other hand, the C-60-MWCNTs composite film effectively suppresses the oxidation of AA. Remarkably, it is found that the oxidation current of DA is over 2 times higher than that of AA even when the concentration of AA is about 3 to 4 orders of magnitude higher than that of DA. This offers a tremendous advantage for the simple and clean detection of DA free of the interfering AA signal in a real assay. Cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectrometry are used to characterize the C-60-MWCNTs composite film. These novel properties are interpreted to arise from the facile electron transfer between C-60 and MWCNTs in the C-60-MWCNTs nanocomposite film

A catalytic nanostructured cobalt oxide electrode enables positive potential operation for the cathodic electrogenerated chemiluminescence of Ru(bpy)(3)(2+) with dramatically enhanced intensity

We report the first novel cathodic electrochemiluminescence of Ru(bpy)(3)(2+) at positive potential of +0.6 V (vs. Ag/AgCl) with a strong light emission clearly visible to the naked eye triggered by reactive oxygen species O-2(center dot-) on an in situ electrodeposited Co3O4 nanostructured electrode

Electrochemistry of Sc3N@C-78 and Sc3N@C-80 (I-h): On achieving reversible redox waves of the trimetal nitride endohedral fullerenes

Electrochemical behavior Of Sc3N@C-78 Solution was investigated for the first time by cyclic voltammetry (CV) as well as differential pulse voltammetry (DPV). Reversible redox features Of Sc3N@C-78 were obtained in contrast to that of Dy3N@C-78, for which the corresponding redox waves were very recently found to be irreversible. Toluene/MeCN and four other solvents have been identified, wherewith reversible redox waves can also be observed for Sc3N@C-80 (I-n) at a normal potential scan rate, whereas o-dichlorobenzene (o-DCB) was found to give only irreversible redox behavior as concluded by other researchers. The redox properties Of Sc3N@C78 and Sc3N@C-80 (I-n) are comparatively discussed on the basis of their different electronic structures and interactions with the solvent molecules. Additionally, electrochemical energy gaps of both Sc3N@C78 and Sc3N@C-80 (I-n) were obtained. (c) 2007 Elsevier B.V. All rights reserved