Nanobiophotonics

Proc. SPIE 8073, 80732J (2011); doi:10.1117/12.886846 Microstructured optical fibers (MOFs) represent a promising platform technology for new biosensing devices. Using MOFs with adapted cavity diameters of about 20 to 30 μm, they can be used to carry the biofluids of analytical interest. Such cavities with their walls coated by transducer material form in combination with adequate microfluidic chips a platform for fully integrated next generation plasmonic devices. This paper describes the use of a dynamic chemical nanoparticle layer deposition (NLD) 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. Electron micrographs, taken of the inside of the fiber holes, confirm the even distribution of the NP. With the proposed procedure fiber lengths of several meters can be coated and afterwards cut up into small pieces of desired lengths. Accordingly, this procedure is highly productive and makes the resulting MOF-based sensors potentially cost efficient. In proof-of-principle experiments with liquids of different refractive indices, the dependence of the localized surface plasmon resonance (LSPR) on the surroundings was confirmed. Comparing Raman spectra of NP coated and uncoated MOFs, each filled with crystal violet, a significant signal enhancement demonstrates the usability of such functionalized MOFs for surfaceenhanced Raman spectroscopy (SERS) experiments.