Biological sensor based on localized surface plasmon associated with surface-bound Au/polystyrene composite microparticles

We describe here a simple method for forming uniform surface-bound Au particles by using as a template monodisperse polystyrene spheres with diameters in the range of 100 to 350 nm; a dense submonolayer of the sphere was first formed on a substrate, followed by evaporation of Au. Cap-shaped Au particles were formed on the top half of the sphere. The particles exhibited strong optical absorption in the UV - near IR range whose peak position depended on the refractive index of the immediate environment. We show how the particle can be patterned on a substrate as well as modified with biomolecules in anticipation of incorporating the particles as a miniature biological sensor into micro analytical devices.