A novel strategy to modify the plasmonic interface by spin-coating an overlayer of graphene oxide sheets (GOSs) on top of the surface plasmon resonance (SPR) sensor is proposed and demonstrated. Thanks to the excellent electrical conductivity, large surface area, and high-refractive index of the GOSs layer, the GOSs-modified SPR (GOSs-SPR) sensor achieves an improved sensitivity in the detection of bulky refractive index solutions and bovine serum albumin (BSA) solutions. The maximum sensitivity of 2715.1 nm/RIU achieved by three spin-coatings shows an enhancement of 20.2% than the case without the modification of the GOSs overlayer. Benefiting from the large surface area and abundant surface functional groups, the GOSs-SPR sensor has a greater sensitivity enhancement (up to 39.35%) in the detection of the BSA molecules. Most importantly, we have firstly experimentally demonstrated that the GOSs overlayer with thickness over hundreds nanometers can still lead to a great enhancement of sensitivity of SPR sensors. Additionally, the proposed modification method for the plasmonic interface is a simple and effective strategy to boost the sensitivity in a chemical-free and environment-friendly manner, without additional chemical or biological amplification steps. These unique features make the proposed GOSs-SPR biosensor a low-cost and biocompatible platform in the fields of biochemical sensing, drug screening, and environmental monitoring.
Keywords: bovine serum albumin; graphene oxide sheets; plasmonic interface; refractive index; sensitivity enhancement.