Enhancing bright-field image of microorganisms by local plasmon of Ag nanoparticle array

Inspecting biological cells with bright-field light microscopy often engenders a challenge, owing to their optical transparency. We show that imaging contrast can be greatly enhanced as yeast cells are placed on a silver nanoparticle array. Its near- and far-field traits, revealed by electrodynamic simulations, illustrate that the enhancement is attributed to the sensitivity of its plasmonic characteristics to the attached cells. This study demonstrates that the silver nanoparticle array can serve as the agent for concurrently enhancing Raman scattering and imaging contrast of microorganisms for identification and examination.