Encapsulation of Conjugated Oligomers in Single-Walled Carbon Nanotubes: Towards Nanohybrids for Photonic Devices By Maria Antonietta Loi,* Jia Gao, Fabrizio Cordella, Pascal Blondeau, Enzo Menna, Barbora Ba ´rtova ´, Ce ´cile He ´bert, Sorin Lazar, Gianluigi A. Botton, Matus Milko, and Claudia Ambrosch-Draxl Dedicated to Prof. Gianfranco Scorrano on the occasion of his 70 th birthday Building robust optoelectronic devices at the atomic scale is one of the challenges faced by nanotechnology. Single-walled carbon nanotubes (SWNTs) are extremely robust nano-objects that exhibit unique electron transport, but their small bandgap limits them to be only near infrared emitters. [1,2] In contrast, organic molecules having outstanding photophysical properties often suffer from low stability and poor electrical characteristics. Exploiting the advantages of both SWNTs and organic molecules opens the prospective to obtain fascinating systems with one- dimensional charge transport and light emission in the visible spectral range. A promising strategy to achieve this is to make use of the hollow space within SWNTs (so-called pods) to accom- modate organic molecules (so-called peas) creating a new hybrid system. [3] Here we demonstrate a nanohybrid with light emitting properties in the visible spectral range obtained by encapsulating thiophene oligomers in SWNTs. By Raman spectroscopy and high-resolution transmission electron microscopy (HRTEM) we have revealed the endohedral position of the guest molecules. Surprisingly, these are not situated in a single array in the center of the tube but are instead arranged in two lines along the sidewalls. Density functional theory (DFT) including van der Waals interactions provides the maximal binding energy for the molecules in cofacial arrangement. The hybrids show photo- luminescence in the visible range while a reduced lifetime of the excited state is symptomatic of molecule–SWNT electronic interactions. We suggest this class of supramolecular hybrids as a promising compact and robust source of photons for the next generation of photonic and optoelectronic devices. Since the discovery in 1998 that the hollow space inside SWNTs could be filled, various atoms and molecules have been encapsulated, including: fullerenes, fullerene derivatives, alkali metal and metallocenes. [4–7] Several experimental and theoretical investigations have shown that the physicochemical properties of COMMUNICATION www.MaterialsViews.com www.advmat.de [*] Dr. M. A. Loi, J. Gao, Dr. F. Cordella Zernike Institute for Advanced Materials University of Groningen Nijenborgh 4, Groningen, 9747 AG (The Netherlands) E-mail: M.A.Loi@rug.nl Dr. P. Blondeau, Dr. E. Menna ITM-CNR and Dipartimento di Scienze Chimiche Universita ` di Padova Via Marzolo 1, 35131 Padova (Italy) Dr. B. Ba ´rtova ´, Prof. C. He ´bert EPFL SB-CIME & IPN-LSME, Ba ˆtiment MXC Station 12, CH-1015 Lausanne (Switzerland) S. Lazar FEI Electron Optics 5600 KA Eindhoven (The Netherlands) Prof. G. A. Botton Canadian Centre for Electron Microscopy Department of Materials Science and Engineering McMaster University 1280 Main Street West, Hamilton, Ontario, L8S 4M1 (Canada) Dr. M. Milko, Prof. C. Ambrosch-Draxl Chair of Atomistic Modelling and Design of Materials, University of Leoben Franz-Josef-Straße 18, A-8700 Leoben (Austria) DOI: 10.1002/adma.200903527 Figure 1. Nanohybrids and their functionality. Top: cartoon of the visible light emitting 6T@SWNT peapod. Bottom: schematic of the encapsulation of a-sexithiophene molecules in SWNTs. The yellow color indicates the sulfur, blue the carbon, and white the hydrogen atoms. Adv. Mater. 2010, 22, 1635–1639 ß 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1635