Delivered by Ingenta to: Chinese University of Hong Kong IP: 141.101.132.48 On: Sun, 12 Jun 2016 09:30:53 Copyright: American Scientific Publishers RESEARCH ARTICLE Copyright © 2013 American Scientific Publishers All rights reserved Printed in the United States of America Journal of Nanoscience and Nanotechnology Vol. 13, 1403–1405, 2013 Two-Dimensional Self-Assembly of Dendritic Amphiphilic Molecule with Ferroncenyl Subsitutuents at the Liquid/Solid Interface Xinrui Miao, Zhiyu Cheng ∗ , Li Xu, Biye Ren, and Wenli Deng ∗ College of Materials Science and Engineering, South China University of Technology, China, Guangzhou 510640, China Two-dimensional self-assembly of dendritic amphiphilic molecule with ferroncenyl subsitutuents (2,3,4-tri-(11-ferroncenyl)undecyloxybenzoic acid, Fc 3 COOH) on highly oriented pyrolytic graphite surface was investigated by scanning tunneling microscopy at the liquid/solid interface. Fc 3 COOH molecule formed an ordered molecular nanostructure—an alternating big/small bright dots pattern on the graphite surface extended to several hundred nanometers. On the basis of the simulation and combined with our STM results, it is concluded that the molecular adsorption conformation has an appreciable effect on the interactions of molecule–molecule and molecule-substrate. The – interactions between ferrocene groups together with the van der Waals interactions between alkyl chains direct the stacking behavior of Fc 3 COOH molecules. Due to the steric constraints, no hydrogen bonding between the carboxyl groups was formed during the self-assembly. Keywords: Self-Assembly, Scanning Tunneling Microscopy, Ferrocene, Dendritic Amphiphilic Molecule. 1. INTRODUCTION The development of dendrimer chemistry is due to the extraordinary pallet of unique properties of these monodis- perse polymers which have applications in numerous fields, such as biology, material science, catalysis, surface mod- ification, electrooptics, chemical or biological sensors. 1–3 Ferrocene has been widely investigated because of its diverse properties in redox reaction, chemical catalysis and easy decomposition of ligands. 4–5 Dendritic amphiphilic molecule with ferroncenyl subsitutuents has their com- bined special characteristic. Surface chemistry and adsorp- tion features of ferrocene on different surfaces have been extensively investigated because they could pro- vide the theoretical support for the potential applica- tion of ferrocenes. In most cases, the self-assembly of ferrocene derivatives were studied on metal surface by scanning tunneling microscopy (STM). 6–10 Especially, Chi group systematically investigated the self-assembly of the oligoethylene-bridged diferrocenes on different metal surfaces. 6 7 9 However, to the best of our knowledge, few reports focused on their nanostructures on highly oriented pyrolytic graphite (HOPG) surface at the liq- uid/solid interface. Up till now, Wedeking et al. reported ∗ Author to whom correspondence should be addressed. the tetradecylferrocene molecule formed an ordered mono- layer on HOPG surface. 9 Our previous studies reported that 2,3,4-tri-(11- ferroncenyl)undecyloxybenzoic acid (Fc 3 COOH) in dimethylformamide solution exhibited good diffusion- controlled redox reversibility, and the three substituents of the compound did not interact strongly with one another but they exhibited a similar redox activity. 11–12 Under- standing the self-assembly of such dendritic amphiphilic molecule will be helpful to comprehend the intermolecular interactions. In addition, it is well known that physical and chemical properties of various low-dimensional materials predominantly relay on the formation of ordered structure. The physical molecular ordering is commonly dominated by the adsorbate–adsorbate and adsorbate-substrate inter- actions. The comparable strength of intermolecular and molecule-substrate interactions makes the self-assembled pattern sensitive to the balance of these interactions and induced certain complicated structures. Thus, in this work, the self-assembly of dendritic amphiphilic molecule with ferroncenyl subsitutuents (Fc 3 COOH) on highly oriented pyrolytic graphite surface by STM at the liquid/solid interface was investigated. We observed a uniform molec- ular assembly exhibiting an alternating big/small bright dots pattern. On the basis of the simulation and combined with our STM results, it is concluded that the  – J. Nanosci. Nanotechnol. 2013, Vol. 13, No. 2 1533-4880/2013/13/1403/003 doi:10.1166/jnn.2013.6100 1403