Eur. Phys. J. Special Topics 224, 2001-2010 (2015)
https://doi.org/10.1140/epjst/e2015-02517-5

Regular Article

Detection of Rhodamine 6G at low concentrations using Raman Spectroscopy: A comparison between Ag and Au-based nanoporous substrates

¹ Aix Marseille Université, CNRS, MADIREL UMR 7246, Centre de Saint-Jérôme, Avenue Escadrille Normandie Niemen, 13397 Marseille Cedex 20, France
² Aix Marseille Université, CNRS, IMBE, UMR 7263, Biogénotoxicologie – Santé Humaine et Environnement, Faculté de Pharmacie, 27 boulevard Jean Moulin- CS30064, 13385 Marseille Cedex 5, France
³ Aix Marseille Université, CNRS, PIIM UMR 7345, Centre de Saint-Jérôme, Avenue Escadrille Normandié Niemen, 13397 Marseille Cedex 20, France
⁴ Aix Marseille Université, CNRS, ICR UMR 7273, Centre de Saint-Jérôme, Avenue Escadrille Normandie Niemen, 13397 Marseille Cedex 20, France
⁵ IM2NP, UMR 7334, Site de l'Université de Toulon – CNRS, BP. 132, 83957 La Garde Cedex, France

Received: 4 December 2014
Revised: 21 May 2015
Published online: 30 July 2015

Abstract

The detection of R6G on nanoporous susbtrates at low concentrations (10⁻⁴ M < C < 10⁻⁷M) was studied coupling its thermodynamic adsorption properties and its Raman response. Two susbtrates were used, they consist in a mesoporous silica matrix in which Ag or Au nanoparticles are incorporated. From a thermodynamic point of view, it was evidenced, using adsorption isotherms and enthalpies, that R6G presents a higher affinity towards Ag@SiO₂ than Au@SiO₂. Furthermore, for C >1.10⁻⁶ M, it was evidenced that R6G Raman response does not depend on metal chemical nature. It is linearly correlated to R6G adsorbed amounts, evidencing the pre-concentration property of the substrates. For lower concentrations, differences were observed in Raman responses. For C = 1.10⁻⁶ M, the Raman bands of R6G adsorbed on SiO₂ and Au@SiO₂ are similar to those found at higher concentrations. For Ag@SiO₂, two new bands, corresponding to bending modes of ethylamine groups, are present as well as the band related to Ag-N stretching mode. This was explained by the specific interaction developed between R6G and Ag@SiO₂. For C = 1.10⁻⁷ M, only the two bands related to R6G ethylamine groups are present for all substrates and a Raman signal enhancement was found for Ag-based substrate.