Microstructured optical fiber with homogeneous monolayer of plasmonic nanoparticles for bioanalysis

Microstructured optical fibers (MOFs) represent a promising platform technology for fully integrated, next generation plasmonic devices. This paper details the use of a dynamic chemical deposition technique to demonstrate the wet chemical deposition of gold and silver nanoparticles (NP) within MOFs with longitudinal, homogenously-distributed particle densities. The plasmonic structures were realized on the internal capillary walls of a three-hole suspended core fiber. The population density of the NP on the surface, which directly influences the usable / necessary sensor length, can be tailored via the controlled pre-treatment of the fiber. With the proposed procedure we can coat several meters of fiber and, afterwards, cut the fiber into the desired lengths. Accordingly, this procedure is highly productive and makes the resulting MOF-based sensors potentially very cheap. Electron microscope micrographs, taken of the inside of the fiber holes, confirm the even distribution of the NP. A transversal through-light setup was used for the non-destructive layer characterization. In proof-of-principle experiments with liquids of different refractive indices, the LSPR dependence on the surroundings was confirmed and compared with Mie-theory based calculations.