Exploring the potentiality of RGO-AuNPs hybrids towards electroanalytical sensor applications

In this work, a novel synthetic route for the synthesis of hybrid materials made of colloidal nanoparticles (NPs) and graphene-based electrodes is presented. In more details, Reduced Graphene Oxide (RGO) sheets are surface modified by functionalized pyrene linkers. The chemical groups of pyrene act as growing sites for the in-situ synthesis of gold nanoparticles (Au NPs) of different dimensions (approximatively 2, 13 and 20 nm). The surface of the colloidal NPs is functionalized with two different capping agents: in one case oleylamine and in the other 3,4-dimethylbenzenethiol. The as prepared hybrid materials are deposited onto Carbon Screen Printed Electrodes (C-SPEs) as a support and are investigated by means of Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) measurements. Particular attention is payed to the role played by every single hybrid component, resulting in a synergistic effect, which is responsible of the enhancement of the hybrid electrochemical properties. The charge transfer from Au NPs to RGO, assisted by the pyrene linker, seems to be the key point to understand the peculiarities of this innovative material. Moreover, the presence or the absence of the Au NP capping agent reflects in different electrochemical responses, depending on the electrode format. The prepared RGO-Au NPs hybrids have been used as electroanalytical sensors for the detection of both inorganic and organic species (arsenic, H2O2, dopamine), showing promising results, in terms of sensitivities and detection limits. In particular, regarding the detection of the neurotransmitter dopamine, the best performances were obtained with Differential Pulse Voltammetry (DPV): a LOD of (3.3 ± 0.2) ppb has been reached, comparable with other electroanalytical results reported in literature, and in accordance with the benchmark for this molecule [1]. In the case of arsenic detection, the hybrid devices show increased performances in comparison with bare Au or organic-coated Au NPs, also allowing speciation between arsenic (III) and (V), appropriately adjusting the experimental conditions. In the case of H2O2, the hybrid devices display high electrocatalytic activity and fast electron-transfer kinetics, representing an ideal platform for developing oxidoreductase-based electrochemical biosensors, as well as for detecting H2O2 in real samples. References [1] J.A. Ribeiro, P.M.V. Fernandes, C.M. Pereira, F. Silva, Talanta 160 (2016) 653-679. Acknowledgements The authors acknowledge the MIUR National Project PRIN 2012 (prot. 20128ZZS2H).