About this Journal Submit a Manuscript Table of Contents
Advances in Physical Chemistry
Volume 2010 (2010), Article ID 289371, 11 pages
http://dx.doi.org/10.1155/2010/289371
Research Article

Combined Electrostatic-Covalent Building of Au NPs Multilayers and Their Size-Enhanced Cohesive and SERS Properties

Institut de Science des Matériaux de Mulhouse, IS2M-CNRS/UHA, 15 Rue Jean Starcky, 68057 Mulhouse, France

Received 21 September 2010; Revised 9 November 2010; Accepted 30 December 2010

Academic Editor: Konstantin Neyman

Copyright © 2010 K. Mougin et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Multilayers of well-ordered and close-packed 2D nanostructures of gold nanoparticles (NPs) were fabricated using a layer-by-layer technique. Colloidal spherical Au NPs of 5 and 15 nm diameters were synthesized and, respectively, self-assembled in multilayers. The robustness of these systems was insured by a combination of electrostatic and covalent bonds between nanoparticles and linker molecules. The compacity of the superlattice was characterized by AFM observation and ellipsometry measurements. Evidence of stronger cohesion of multilayers of smaller NPs size was brought by submitting the systems to sonication test. The multilayers have also proved analytical potential when used to detect low concentration methylene blue molecules adsorbed on the Au nanoparticles, by surface-enhanced Raman spectroscopy (SERS). The detection sensitivity of these two sized Au NPs architectures was directly compared to an evaporated “bulk” Au thin film of equivalent thickness. Results have displayed a strong increase of the electromagnetic field enhancement with a decrease of the NPs size, whereas the bulk thin Au film was shown to be inefficient as a SERS substrate. These results bring a nice evidence of size effects on the global performance (SERS, cohesion) and hopefully on the stability of NPs based nanostructures.