Good Solvent Effects of C-70 Cluster Formations and Their Electron-Transporting and Photoelectrochemical Properties
ABSTRACT Good solvent effects of C(70) cluster formations and their electron-transporting and photoelectrochemical properties have been systematically examined for the first time. Nano-to-micrometer scale assemblies of C(70) with different morphologies were prepared by rapidly injecting poor solvent (i.e., acetonitrile) into a solution of C(70) dissolved in various good solvents (i.e., benzene, toluene, chlorobenzene, etc). The cluster morphology engineering was successfully achieved by changing the good solvent, yielding the spherical, rodlike, or platelike clusters in the mixed solvents. The clusters of C(70) were electrophoretically deposited onto a nanostructured SnO(2) electrode to examine the photoelectrochemical properties under the white light or monochromatic light illumination. The maximum incident photon-to-current efficiency (IPCE) varied from 0.8 to 10% depending on the combinations of the poor-good solvents. The differences in the IPCE values are discussed in terms of the surface area, thickness, and electron mobility of the deposited cluster films. The electron mobility is found to be the most predominant factor for the IPCE, indicating the importance of the electron-transporting process in the overall photocurrent generation. In addition, the electron mobility is closely correlated with the underlying molecular alignment and the resultant cluster structure. Thus, these results will provide basic clue for the design of C(70)-based molecular devices including the organic photovoltaics.
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ABSTRACT: We present deposition of uniform polyfullerene films on ITO substrates using a novel electrochemical concept based on the oxidation of C60 dianion (C) solution. The C solution was prepared by the electroreduction of the C60 solution in dichloromethane and its oxidation at ITO surface was carried out using linear sweep voltammetry (LSV) in the −1 to 0 V range. The electrodeposited films were characterized by various techniques, such as, scanning electron microscopy, atomic force microscopy, Kelvin probe microscopy, high-resolution transmission electron microscopy, UV/Vis and Fourier transform infrared spectroscopy. The morphology of electrodeposited polyfullerene film was found to depend upon numbers of LSV scans used for its preparation. After 100 LSV scans, the films exhibited a globular morphology and were found to make a full coverage of ITO substrate. At higher scans, a second layer of polyfullerene was found to grow in the form of whiskers having length and diameter upto 200 and 0.4 µm, respectively. The energy band gap for polyfullerene whiskers was found to be ~0.7 eV. Experimental evidence show that C60 polymerizes in the 1-dimensional “pearl-structure” via [2+2] cycloaddition reaction.Journal of The Electrochemical Society 01/2012; 159:D13. DOI:10.1149/2.021201jes · 2.86 Impact Factor
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ABSTRACT: Solubilization of fullerenes is of high interest because of their wide usage in both fundamental research and numerous applications. This paper reports molecular dynamics (MD) simulations of saturated and supersaturated solutions of C60 in 1-butyl-3-methylimidazolium tetrafluoroborate, [C4C1IM][BF4], room-temperature ionic liquid (RTIL). The simulations cover a wide range of temperatures between 280 and 500 K at ambient pressure. Unlike in simpler solvents, C60 in [C4C1IM][BF4] forms highly supersaturated solutions, whose internal arrangement remains unaltered during nearly a microsecond-long real-time dynamics. The ion-molecular structure patterns in saturated and supersaturated solutions are distinguished in terms of radial distribution functions and cluster analysis of the solute particles. Cation separated solute pair is found to be a common structure in both saturated and supersaturated solutions. This observation suggests that imidazolium cation plays an important role in the successful dispersion of C60 molecules. Anticipated practical applications of the observed phenomenon are briefly discussed.The Journal of Physical Chemistry B 06/2014; 118(26). DOI:10.1021/jp5020725 · 3.30 Impact Factor