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Tuning the collective switching behavior of azobenzene/Au hybrid materials: flexible versus rigid azobenzene backbone and Au(111) surface versus curved Au nanoparticle

Abstract

The combination of photo-responsive azobenzene (AB) and biocompatible Au nanomaterial possesses potential applications in diverse fields such as biosensor and thermotherapy. To explore the influence of azobenzene moities and Au substrates on the collective switching behavior, two different azobenzene derivatives (rigid biphenyl-controlled versus flexible alkoxyl chain-linked) and three different Au substrates (planar Au(111) surface, curved Au102(SR)44 and Au25(SR)18 clusters) were chosen to form six Au@AB combinations. A reactive molecular dynamics (RMD) model considering both torsion and inversion path was implemented to simulate the collective photo-induced cis-to-trans switching process of AB monolayers on Au substrates. The major driving force for isomerization is demonstrated to be the torsion of the C-N=N-C dihedral angle, in accompany with minor contribution from an inversion pathway. The isomerzation process can be decomposed into the preliminary conformation switching stage and the latter relaxation stage, in which a gradual self-organization is observed during 40 ps. The Au substrate affects the packing structure of AB monolayer, whilst the choice of different kinds of ABs tunes the intermolecular interaction in the monolayer. Flexible alkoxyl-linked F-AB may achieve much faster conversion on Au cluster than on surface. For rigid biphenyl-based R-AB anchored on Au nanoparticle (AuNP), a competitive torsion between the biphenyl and C-N=N-C dihedral may delay the C-N=N-C dihedral torsion and the following isomerization process. After the R-AB molecules being anchored on Au(111) surface, the strong π-π stacking between biphenyl units accelerates the collective isomerization process. A curvature-dependent effect is observed for R-AB SAMs on different-sized substrates. The cooperation between functional AB monolayers and Au substrate determines the collective switching behavior of Au@AB materials. These results are expected to guide rational designs of Au@AB hybrid materials for different usages.

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Supplementary files

Publication details

The article was received on 14 May 2017, accepted on 02 Oct 2017 and first published on 02 Oct 2017


Article type: Paper
DOI: 10.1039/C7NR03421K
Citation: Nanoscale, 2017, Accepted Manuscript
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    Tuning the collective switching behavior of azobenzene/Au hybrid materials: flexible versus rigid azobenzene backbone and Au(111) surface versus curved Au nanoparticle

    C. Liu, D. Zheng, W. Hu, Q. Zhu, Z. Tian, J. Zhao, Y. Zhu and J. Ma, Nanoscale, 2017, Accepted Manuscript , DOI: 10.1039/C7NR03421K

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