Graphene oxide-assisted surface plasmon coupled emission for amplified fluorescence immunoassay

We have observed the unique enhancement of fluorescence signal of surface plasmon coupled emission (SPCE) by graphene oxide (GO) on gold film. Assembling ultrathin GO by electrostatic adsorption between gold film and fluorophore layer (about 30 nm), the enhancement of fluorescence signal of SPCE reached 7 and 25 times respectively as compared to that of the regular SPCE and free space emission (FSE) without GO. The enhancement factors were studied through modifying different concentrations of GO and thicknesses of fluorophore layer, and the possible enhancement mechanisms were investigated. This GO-assisted SPCE was designed as an immunosensor to detect human IgG with a detection limit of 0.006 ng/mL, which was much lower than the detection limit of immunosensor based on regular SPCE. This strategy combing GO and SPCE to enhance the fluorescence signal provides a simple way to improve detection sensitivity in fluorescence-based sensing platforms.