Tailoring multifunctional graphene-based thin films: from nanocatalysts to SERS substrates

Abstract

Anchoring different functional groups on graphene may modulate and broaden its application, providing free groups to act for example as catalytic sites or for metallic nanoparticles (NPs) passivation. In this work, two novel approaches, based on the liquid/liquid (L/L) interfacial method, were used to obtain thiolated graphene oxide (GO) thin films rationally modified with cysteamine, through stable amide bonds, with different degrees of functionalization. In addition, nanocomposites of the functionalized film with silver nanoparticles (Ag-NPs) were obtained by the direct heterogeneous reaction of Ag⁺ cations with the films. The functionalized films were applied as nanocatalysts for organophosphate degradation, as SERS substrates and finally as a SERS-based qualitative sensor for nitrophenols. The thin film nanocomposites presented high performance in the detection of 4-aminothiophenol with enhancement factors up to 10⁸. Moreover, the thiolated thin films were effective catalysts for degrading organophosphates such as the toxic pesticide Paraoxon, which presented impressive catalytic activity (10⁶-fold). Elegantly, we managed to detect by Raman spectroscopy the degradation product adsorbed on the nanocomposite catalyst, hence achieving a SERS sensor for nitrophenol. Thus, we report for the first time the synthesis of functionalized graphene-based thin films through the interfacial route and their nanocomposites with Ag-NPs, along with their multiple applications. In fact, tailoring such multifunctionalities is particularly interesting for the development of sensors and detoxifying agents to monitor and eradicate abusive uses of toxic organophosphorus substances.