Bulk quantity and physical properties of boron nitride nanocapsules with a narrow size distribution Ewa Borowiak-Palen a,b, * , Mark H. Ru ¨mmeli a , Martin Knupfer a , Gu ¨nter Behr a , Kati Biedermann a , Thomas Gemming a , Ryszard J. Kalenczuk b , Thomas Pichler a a Leibniz-Institute for Solid State and Materials Research Dresden, P.O. Box 270016, Dresden D-01171, Germany b Institute of Chemical and Environment Engineering, Technical University of Szczecin, Poland Received 15 January 2004; accepted 18 October 2004 Available online 2 December 2004 Abstract A new synthesis route for the formation of boron nitride (BN) nanocapsules by means of a substitution process using single wall carbon nanotubes as templates, with yields of >95% is presented. It is also shown that these BN nanocapsules can act as ideal ref- erence samples for the determination of the relative sp 2 to sp 3 configuration in BN species, a value that is crucial for the physical properties of these nanostructures. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: B. Heat treatment; C. Electron energy loss spectroscopy, Infrared spectroscopy; Raman spectroscopy; Transmission electron microscopy 1. Introduction Concentric shell carbon clusters, also referred to as carbon onions, were first discovered by Ugarte [1] in 1992. Due to the structural similarity of h-BN and graphite, the formation of concentric shell BN nano- structures (spherical clusters with incomplete closed shells, encapsulated polyhedral BN nanoparticles or BN onions and nested BN fullerenes) came as no sur- prise [2–11]. The ever-increasing interest in BN nano- structures is based on their large band gap leading to potential applications in photoluminescence devices [12] and nano-electronic-magnetic devices [13]. These nanostructures have been synthesized by various tech- niques, namely, by carbothermal reduction of ultra dis- persed amorphous boron oxide in the presence of nitrogen [7], intense electron irradiation in transmission electron microscopes using different reactants [4,6], polymer pyrolysis, chemical reaction, arc-melting and electron-beam irradiation [9]. However, thus far, with all of these methods, BN nanocapsules are only present as one or a few among many BN species, for example h-BN sheets and BNNT. The substitution reaction of carbon nanotubes used for the production of diverse heteronanotubes [14–19] is also a suitable method to ob- tain fullerene like BN nanostructures here referred to as ‘‘nanocapsules’’. In this work we present an adapted substitution pro- cess that has been optimized for the preparation of BN nanocapsules in high yields, cf. high yield carbon onion production [20]. Both the quality of the product and the efficiency of this method were characterized using trans- mission electron microscopy (TEM), electron energy loss spectroscopy (EELS) in terms of core excitation edges, optical absorption spectroscopy (OAS), in partic- ular the infrared (IR) regime and Raman spectroscopy. To the best of our knowledge this is the first time such 0008-6223/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbon.2004.10.032 * Corresponding author. Address: IFW-Dresden, Germany, Sur- faces and Interfaces, Helmholtzstr. 20, Dresden D-01171, Germany. Tel.: +49 351 4659 501; fax: +49 351 4659 537. E-mail address: e.borowiak@ifw-dresden.de (E. Borowiak-Palen). Carbon 43 (2005) 615–621 www.elsevier.com/locate/carbon