Electrostatically mediated layer-by-layer assembly of a bioinspired thymine polycation and gold nanoparticles

FLORENCIA A. GULOTTA, VERÓNICA I. PAZ ZANINI, BEATRIZ A. LÓPEZ DE MISHIMA, ; DEBORA MARTINO; OMAR E. LINAREZ PEREZ, FERREYRA NANCY F

JOURNAL OF ELECTROANALYTICAL CHEMISTRY

ELSEVIER

Lugar: Amsterdam; Año: 2020 vol. 883 p. 114895 - 114904

0022-0728

In this work, we built self-assembled structures of gold nanoparticles (AuNPs) using a new polyelectrolyte formed bycopolymerization of the monomers 4-vinylbenzyl thymine (VBT) and 4-vinylbenzyl triethylammonium chloride(VBA). For the synthesis, a monomer ratio of 1 mol of VBT to 16 mol of VBA was used to obtain the polycation[(VBT)1:(VBA)16]16+ with a charge density suitable for the electrostatic adsorption of citrate stabilized AuNPs. The ob-jective of this work was to explore the optical and electrochemical properties of the structure built on gold and quartzsubstrates with a view to its potential application as a (bio)sensor for optical and electrochemical detection. Thepolycation adsorption process was studied by surface plasmon resonance, which allowed us to select the appropriateconcentration and adsorption time for the polymer and verify the formation of the self-assembly. Characterization ofthe system by atomic force microscopy allowed determining that AuNPs are distributed in isolation, such as dimers,trimers, tetramers, or bigger aggregates. The analysis of the resonance of the localized surface plasmons (LSPR) ofthe AuNPs, as well as the increase in the intensity of the polycation Raman signals revealed the electromagnetic cou-pling between close nanoparticles. In addition, the electrochemical impedance spectroscopy study of gold electrodesmodified with the ([(VBT)1:(VBA)16]16+/AuNPs)n multilayer showed that incorporation of the AuNPs in the structureproduced an increase in the apparent heterogeneous charge transfer constant. This fact indicates that the structure ofthe film and the nanoparticles distribution favor the electronic conduction mediated by AuNPs. The observed proper-ties indicate that this multilayer represents a very interesting platform for the development of (bio)sensors based onoptical or electrochemical detection