Large-area SPR imaging of nanoparticles using crossed diffraction gratings

We present a new, to the best of our knowledge, surface plasmon resonance (SPR) imaging platform for the visualization of individual nanoparticles (NPs) based on a gold-coated crossed diffraction grating (CDG). The CDG couples incident light with the propagating surface plasmon (SP) and separates the reflected light from the signal generated by the scattering of SP on NPs, thereby reducing background intensity and improving image contrast. We demonstrate the visualization of gold and polystyrene NPs as small as 20 and 60 nm, respectively, with a field of view of ∼20 mm², and show that the presented imaging approach enables visualization of smaller NPs across a larger field of view than conventional SPR imaging platforms.