Reversible end-to-end assembly of selectively functionalized gold nanorods by light-responsive arylazopyrazole-cyclodextrin interaction.

Maximilian Niehues,Patricia Tegeder,Bart Jan Ravoo

doi:10.3762/bjoc.15.140

Abstract

We propose a two-step ligand exchange for the selective end-functionalization of gold nanorods (AuNR) by thiolated cyclodextrin (CD) host molecules. As a result of the complete removal of the precursor capping agent cetyltrimethylammonium bromide (CTAB) by a tetraethylene glycol derivative, competitive binding to the host cavity was prevented, and reversible, light-responsive assembly and disassembly of the AuNR could be induced by host–guest interaction of CD on the nanorods and a photoswitchable arylazopyrazole cross-linker in aqueous solution. The end-to-end assembly of AuNR could be effectively controlled by irradiation with UV and visible light, respectively, over four cycles. By the introduction of AAP, previous disassembly limitations based on the photostationary states of azobenzenes could be solved. The combination photoresponsive interaction and selectively end-functionalized nanoparticles shows significant potential in the reversible self-assembly of inorganic–organic hybrid nanomaterials.

Highlights

Metallic nanomaterials have received intense and interdisciplinary interest due to their unique optical [1], electronic [2,3] and sensing properties [4,5]
CD-end functionalized assembly of host-functionalized gold nanorods (AuNR) were obtained in a two-step ligand exchange procedure as depicted in Scheme 2
For an efficient ligand exchange the primary alcohol groups of β-CD were replaced with thiols by a known two-step synthesis [42,43] to give a multivalent ligand that is tightly bound to the gold surface and is not replaced by an excess of monothiolated tetraethylene glycol

Summary

Introduction

Metallic nanomaterials have received intense and interdisciplinary interest due to their unique optical [1], electronic [2,3] and sensing properties [4,5]. The addition of a divalent AAP linker molecule (dAAP) led to light-responsive reversible self-assembly of AuNR in an end-to-end manner as depicted in Scheme 1 to open up a novel strategy for the design of hybrid nanomaterials by supramolecular chemistry. Scheme 1: Light-responsive end-to-end assembly of host-functionalized gold nanorods (AuNR) by cyclodextrin–AAP interaction.

Results

Conclusion