Infrared surface plasmons in double stacked nickel microarrays: Lipid bilayer systems.

摘要

An individual nickel mesh with a hole-to-hole spacing of 12.7 mum exhibits extraordinary properties in the infrared region, i.e. it transmits more light than is incident upon the holes. This results from propagating surface plasmons which "carry" light incident upon the metal to a hole, allowing it to be reemitted as light on the back side of the mesh. When two such mesh are stacked with a subwavelength spacing, the transmission of the stack mimics that of the single mesh, but the propagating surface plasmons can couple between the meshes producing narrower resonances. Characterization of the resonances shows how they disperse as a function of angle and reveals a splitting of the dispersion curve in momentum space, resulting from the coupling between the front and back surfaces of each mesh and perhaps between the meshes. This coupling phenomenon will be useful for passing infrared radiation through nanospaces enclosed within the mesh stack.;The increased transmission can be exploited by applying a molecular coating to the mesh. The unique properties of the mesh allow the coatings to be studied with increased absorptions, easing the observation of weaker vibrations. Both vapor and solution deposition methods have been studied, with the primary focus herein on lipid bilayer coatings made from solution. Based upon their simplicity and relative importance in membrane studies, three different lipids were chosen for observation in the mesh system individually, as well as in combination with each other or cholesterol, to look for changes in the spectrum indicating interaction between the molecules. In addition, gramicidin, an antibiotic peptide, was observed in a system with one of the lipids (dipalmitoylphosphatidylcholine) as a first approximation for protein interactions. Finally, two relatively simple microorganisms (Saccharomyces cerevisiae - yeast and Escherichia coli - E. coli) were observed on the mesh.