Photochemical and electrochemical synthesis of [rGO–AuNps] hybrids dispersions for detection of rhodamine 6G by SERS

Abstract

Many hybrid nanomaterials with different types of metallic nanostructures have been studied for diverse applications. Herein, we present four simple experimental strategies, combining photochemical and electrochemical reduction steps to obtain aqueous dispersions of hybrid nanomaterials of reduced graphene oxide flakes (rGO) supporting gold nanoparticles (AuNps). We found clear differences in the optical, structural, and morphological characteristics of the [rGO–AuNps] hybrids due to the size, shape, and distribution of AuNps, according to the synthesis strategy employed. These characteristics are associated with the degree of reduction (C/O ratio composition) and structural defects (Raman intensity ratio between D and G bands) of the rGO formed, both features provide sites available for nucleation and growth of the nanostructures, obtained in each synthesis. The efficiency of different dispersions with plasmonic activity in the detection of rhodamine 6 G (Rh6G) from dilute aqueous solutions was spectroscopically evaluated. SERS (Surface-Enhanced Raman spectroscopy) experiments were performed directly on cellulose fibers (filter paper), previously modified with the assembly of the hybrid nanomaterials, and the Rh6G molecules. In this way, a practical and simple configuration with nanomaterials has been established, as a platform designed for the sensitive detection of adsorbed molecules, potentially useful during the filtration of contaminated water. The SERS spectra of adsorbed Rh6G on the paper membranes with the hybrids [rGO]^hυ –[AuNps]^hυ and [rGO]^hυ–[AuNps]^ec for 48 h immersion, showed a 23 ± 5 and 21 ± 5 enhancement factor (EF), respectively.