Chemical functionalization of carbon nanotubes with aryl diazonium salts
- PDF / 480,857 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 105 Downloads / 228 Views
Chemical functionalization of carbon nanotubes with aryl diazonium salts Anastasia A. Golosova, 1 Christine M. Papadakis1 and Rainer Jordan 1,2* 1 Wacker-Lehrstuhl für Makromolekulare Chemie, Department Chemie, TU München, Lichtenbergstr. 4, 85747 Garching, Germany. 2 Professur für Makromolekulare Chemie, Department Chemie, TU Dresden, Zellescher Weg 19, 01069 Dresden, Germany. ABSTRACT We describe a facile and direct method for the functionalization of single-walled carbon nanotubes with 4’-substituted phenyls and biphenyls. By means of Raman spectroscopy and thermogravimetric analysis we demonstrate that a simple protocol of a direct chemical grafting in acetonitrile solution of the corresponding diazonium salts at room temperature results in a formation of stable aryl monolayers on carbon nanotubes. INTRODUCTION Carbon nanotubes (CNTs) have attracted much attention because of their mechanical, electrical, and thermal properties [1]. In spite of many attempts to exploit CNTs, e.g. as active fillers in a polymer matrix for obtaining composites with extraordinary characteristics, a number of challenges, e.g. the effective incorporation of CNTs within the surrounding matrix, are still unsolved. Due to the strong van der Waals interactions, hydrophopic CNTs tend to organize into large aggregates, which behave differently from individual CNTs [2]. Moreover, being formed from graphene sheets, which are comprised of sp2-carbon, CNTs are very hydrophobic and almost inert to chemical modifications. Hence, a number of studies were devoted to improve the dispersibility and solubility of CNTs in solvents or in a polymer matrix by means of direct chemical modifications [3]. Among other modifiers, aryl diazonium salts proved to be useful and versatile reagents for a functionalization of the sp2-carbon with a variety of functional groups, and different reaction conditions have been proposed. Modification of small diameter (0.7 nm) single-walled carbon nanotubes (SWCNTs) was achieved via electrochemical reduction of aryl diazonium salts where the formation of reactive aryl radicals was triggered by electron transfer between CNT and aryl diazonium salt [4]. A similar reaction mechanism was suggested for thermal activated modification of SWCNTs with in-situ generated diazonium salts [5]. Later, Tour et al. [6] showed that the use of additional surfactants resulted in a significant improvement of the CNT functionalization because of the better dispersion of the native CNTs. However, the main drawback of most modification reactions involving aryl diazonium salts is the well-known formation of multilayers of p-substituted aryls on the carbon surfaces, as e.g. observed for the electrochemical modification [7] or the reaction in aqueous media [8]. Recently, we reported on the formation of well-defined self-assembled monolayers of 4’substituted biphenyls on ultrananocrystalline diamond by chemical grafting from a saturated solution of the aryldiazonium salt in acetonitrile at room temperature [9,10]. Herein, we report
on the applicatio
