Single-layer graphene-coated gold chip for electrochemical surface plasmon resonance study

Surface plasmon resonance (SPR) employs a gold (Au) thin film (ca. 50 nm in thickness) chip to generate a surface plasmonic wave (SPW) for in situ monitoring of the interface/surface, which makes it intrinsically compatible with electrochemistry for combined electrochemical surface plasmon resonance (EC-SPR) investigations. However, conventional SPR Au chips suffers from a high background signal, narrow electrochemical window, and limited electrochemical stability. Presented in this work is a novel SPR chip composed of the Au/long-chain alkane thiol self-assembled monolayer/single-layer graphene (Au/SAM/G) sandwich architecture to address these problems. On this chip, the single-layer graphene serves as a working electrode for electrochemical measurement, and the underlying Au film serves as the SPW support for SPR monitoring; the sandwiched thiol monolayer enables the electrical separation of the graphene and Au film to protect the Au film from electrochemical polarization. Our experiment indicates that the electrochemical window of such a chip extends beyond the hydrogen/oxygen evolution reaction potential on Au with significantly improved electrochemical stability and suppressed background signal. Moreover, its intrinsic SPR sensitivity is completely reserved even compared to that of the conventional SPR Au chip. This Au/SAM/G chip may offer a valuable solution to the EC-SPR investigations in harsh conditions.