Carbon-Rich Nanostructures from Molecular Precursors
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Carbon-Rich Nanostructures from Molecular Precursors Tobias N. Hoheisel2, Ruth Szilluweit1, Stephen Schrettl1, and Holger Frauenrath1* 1
Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratory of Macromolecular and
Organic Materials, Station 12, 1015 Lausanne, Switzerland 2
ETH Zürich, Department of Materials, Wolfgang-Pauli-Str. 10, 8093 Zürich, Switzerland
ABSTRACT A synthesis for protected, glycosylated, amphiphilic oligo(ethynylene)s was developed. After their deprotection, two different glycosylated hexa(ethynylene)s were investigated for their self-assembly properties as well as their reactivity in aqueous solutions and at the air-water interface. Aggregation was observed in aqueous solution by UV spectroscopy, and the molecules formed films at the air-water interface. INTRODUCTION Carbon-rich nanostructures are intriguing targets both from an academic point of view, and for applications in a wide range of fields [1]. For example, the discovery of graphene has enabled the study of its properties and provided a way to probe quantum electrodynamics phenomena so far known only theoretically [2, 3]. On the other hand, carbon-rich nanostructures are already used as electrode materials in lithium accumulators [4], or in fiber-reinforced composites in the automotive and aerospace industries [5]. Owing to the large interest in carbon-rich nanostructures, a variety of methods has been established for their synthesis. Thus, carbon nanostructures such as fullerenes and carbon nanotubes are synthesized using resistive heating of graphite [6], arc discharge [7, 8], laser ablation [9], and chemical vapor deposition [10]. The most prominent disadvantages of these methods are the low overall yields, the obtained product mixtures, defective structures, and the high temperatures during the synthesis, which preclude a functionalization of the carbon nanostructures during the preparation. In order to overcome these problems, novel approaches have been devised for the synthesis of carbon-rich nanostructures starting from molecular precursors. Thus, Huang and coworkers reported the preparation of hard carbon spheres from sucrose in a hydrothermal process at 190 °C followed by annealing at 1000 °C or 2500 °C in an argon atmosphere [11]. More recently, Antonietti and coworkers discovered that the hydrothermal treatment of carbohydrate precursors in the presence of transition metal salts yielded one-dimensional carbon-inorganic hybrid structures [12]. Similarly, carbon-coated metal nanowires were obtained using poly(vinyl alcohol) and silver nitrate or poly(vinyl alcohol) and tellurium nanowires [13, 14]. These approaches share a beneficially low process temperature. However, the process is difficult to control since virtually nothing is known about the mechanism of this transformation.
A different approach was pursued by Müllen and coworkers, who employed alkyl-decorated, polycyclic aromatic hydrocarbons as molecular precursors. Pyrolysis of alkylated hexa-perihexabenzocoronene derivatives at 800 °C produced a variety of ca
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