Functional nanoimprinted plasmonic crystals for chemical sensing and imaging

We describe here nanoimprinted plasmonic crystals composed of highly uniform subwavelength metal nanohole and nanopost arrays and their application in surface-enhanced sensing and imaging. Soft nanoimprint lithography is a versatile, cost-effective method to precisely replicate these structures with well-characterized optical properties. These plasmonic crystals support multiple surface plasmon modes controlled by the design rules of the nanostructures, allowing us to optimize the devices for operation in a particular wavelength range. We have demonstrated the ability to spectroscopically measure bulk refractive index changes and mechanical deformation of hydrogels resulting from pH changes, thin film imaging with sensitivities down to submonolayer levels using a common optical microscope, and Raman signal enhancement using a single common device framework. These plasmonic crystals have the potential to overcome many of the technological limitations that have limited the widespread application and integration of surface-enhanced analytical techniques.