Flexible, graphene protected Ag nanoparticles–polyimide tape for use as a transparent Surface-Enhanced Raman Scattering (SERS) substrate and its application in pesticide detection

Abstract

A flexible and transparent tape-based SERS substrate consisting of electrodeposited silver nanoparticles (AgNPs) sandwiched between polyimide (PI) tape and a graphene (G) layer was successfully fabricated using the chemical vapor deposition (CVD) of graphene onto a copper substrate, followed by electrodeposition of Ag nanoparticles and transfer to PI tape to obtain the G/AgNPs/PI SERS substrate. Nanostructure formations on the substrate were studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). A rattan ball-like Ag structure with feature gaps of ∼30-100 nm was obtained from the optimized electrodeposition time and current density, which yielded the highest Raman signal enhancement. Methyl parathion (MP) was selected as a probe molecule for investigating the SERS performance, where the MP detection limit of 68 ng/cm2 was achieved. The graphene layer helps to stabilize and protect the Ag nanoparticles. The shelf life of the G/AgNPs/PI substrate at room temperature was extended to longer than 48 days, compared to just 27 days for the SERS substrate without the protective graphene layer. The practicability of this transparent tape-based SERS substrate was successfully demonstrated by detecting the MP residue on apple fruit, where both the light excitation and Raman signal collection were performed from the tape side.