Selective Hybridization of Dendron-Cyclodextrin Nanotubes with Metal Nanoparticles

Abstract

The controlled organization of organic moieties with inorganic elements provides not only unique complex hybrid nanostructures but also synergistic functional properties. [1][2][3] For this purpose, several synthetic approaches have been developed by using organic supramolecules as a template for the construction of organized organic-inorganic hybrid architectures. [4][5][6][7][8][9][10][11][12] In addition, the electronic or chemical communication between organic and inorganic moieties would provide an opportunity to produce unique functional hybrids. 13,14 In particular, organic nanotubes have attracted considerable attention as a template for nanohybrids, 3,15,16 for examples, lipid nanotubes for the template of silica 3,15 and peptide nanofibers for the template of biomineralization. 5,9,11 In particular, fabrication of linear assemblies of inorganic elements is of great interest for the development of nano-devices due to their anisotropic properties in 1-dimensional state. 16 For that purpose, carbon nanotubes are excellent template for the fabrication of linear assembly of inorganic elements. 17,18 In addition, biomolecules such as DNA, 19 peptides, 16 and viruses 20 were used as a template for the organization of nanoparticles. Self-assembled organic nanotubes are particularly advantageous as a template for the linear organization of nanoparticles because the surface anchoring functionality can be efficiently tailored.Recently, we reported on the cyclodextrin-covered organic nanotubes (Den-CD-NTs) constructed by the self-assembly of the amide dendrons with the focal pyrene unit which is included into the cavity of β-or γ-cyclodextrin (CD). 21,22 The narrow rim of CDs is exposed to the surface of the tube. Therefore, the surface functionality of the tube can be controlled in a facile manner during the self-assembly process via the host-guest interaction between the amide dendron and CDs. Therefore, we reasoned that the tunable well-defined surface of Den-CD-NTs would be an effective template for growing inorganic nanoparticles which can electronically communicate with the pyrene moiety included in the cavity of CDs on the surface of the tube. This approach would provide a facile route to unique nanotube-nanoparticle hybrid systems for nanoelectronics or biosensor applications. Herein we present a unique approach to produce the hybrid of organic nanotube and metal nanoparticle by using Den-CD-NTs as a template.We have demonstrated that the amphiphilic amide dendrons can self-organize not only in organic phase but also in aqueous phase. [23][24][25][26][27][28] In particular, amide dendron 1 with the focal pyrene moiety in Figure 1 self-organizes into a vesicular structure in an aqueous phase. Addition of β-CD into the vesicular solution of dendron 1 induces formation of Den-CD-NT of which the surface is covered with β-CD.21 The C-6 functionality of on the narrow of CDs is then exposed to the surface of Den-CD-NTs. This methodology provides a facile synthetic route to diverse Den-CD-NTs with a variety of sur...