Simultaneous transfer of noble metals and three-dimensional micro- and nanopatterns onto zein for fabrication of nanophotonic platforms

In this paper, we report a method to manufacture green nanophotonic sensors made of corn protein zein. The method is direct transfer of three-dimensional metallic (gold and silver) nanostructures onto biodegradable zein films. We have transferred both micro-scale and nano-scale structures with several geometries. Inverted and positive pyramid structures, with 2 μm by 2 μm square base, nanopores, and nanopillars with an approximately 250 nm diameter were successfully transferred onto zein along with 200- and 80-nm-thick gold layers onto pyramids and nanopillars/pores, respectively. Rhodamine 6G was used as a model molecule for surface-enhanced Raman spectroscopy (SERS) measurements, and it was found that the inverted pyramid gold zein sensors had the highest enhancement factor, compared to the other zein sensors. The novel zein sensor platform we developed has the potential to serve as a biodegradable SERS platform for applications in agricultural, medical, and food analysis purposes.