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Open AccessArticle

Supramolecular Control over the Interparticle Distance in Gold Nanoparticle Arrays by Cyclodextrin Polyrotaxanes

1
Departamento de Química Física, Universidad Complutense de Madrid, Avenida Complutense s/n, 28040 Madrid, Spain
2
Departamento de Química Orgánica, Universidad Complutense de Madrid, Avenida Complutense s/n, 28040 Madrid, Spain
3
Departamento de Química en Ciencias Farmacéuticas, Universidad Complutense de Madrid, Plaza Ramón y Cajal s/n, 28040 Madrid, Spain
4
Instituto de Fusión Nuclear, Universidad Politécnica de Madrid, José Gutiérrez Abascal 2, 28006 Madrid, Spain
*
Author to whom correspondence should be addressed.
Nanomaterials 2018, 8(3), 168; https://doi.org/10.3390/nano8030168
Received: 23 February 2018 / Revised: 2 March 2018 / Accepted: 14 March 2018 / Published: 16 March 2018
(This article belongs to the Special Issue Supramolecular Nano-architectures)
Amphiphilic nonionic ligands, synthesized with a fixed hydrophobic moiety formed by a thiolated alkyl chain and an aromatic ring, and with a hydrophilic tail composed of a variable number of oxyethylene units, were used to functionalize spherical gold nanoparticles (AuNPs) in water. Steady-state and time-resolved fluorescence measurements of the AuNPs in the presence of α-cyclodextrin (α-CD) revealed the formation of supramolecular complexes between the ligand and macrocycle at the surface of the nanocrystals. The addition of α-CD induced the formation of inclusion complexes with a high apparent binding constant that decreased with the increasing oxyethylene chain length. The formation of polyrotaxanes at the surface of AuNPs, in which many α-CDs are trapped as hosts on the long and linear ligands, was demonstrated by the formation of large and homogeneous arrays of self-assembled AuNPs with hexagonal close packing, where the interparticle distance increased with the length of the oxyethylene chain. The estimated number of α-CDs per polyrotaxane suggests a high rigidization of the ligand upon complexation, allowing for nearly perfect control of the interparticle distance in the arrays. This degree of supramolecular control was extended to arrays formed by AuNPs stabilized with polyethylene glycol and even to binary arrays. Electromagnetic simulations showed that the enhancement and distribution of the electric field can be finely controlled in these plasmonic arrays. View Full-Text
Keywords: supramolecular chemistry; self-assembly; gold nanoparticle; cyclodextrin; polyrotaxane; array; hot spot; surface-enhanced spectroscopy supramolecular chemistry; self-assembly; gold nanoparticle; cyclodextrin; polyrotaxane; array; hot spot; surface-enhanced spectroscopy
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Paulo Coelho, J.; Osío Barcina, J.; Junquera, E.; Aicart, E.; Tardajos, G.; Gómez-Graña, S.; Cruz-Gil, P.; Salgado, C.; Díaz-Núñez, P.; Peña-Rodríguez, O.; Guerrero-Martínez, A. Supramolecular Control over the Interparticle Distance in Gold Nanoparticle Arrays by Cyclodextrin Polyrotaxanes. Nanomaterials 2018, 8, 168.

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