Measurement and Optimization of Metal‐Nanoparticle‐Induced Luminescence Enhancement Factors in a Crossed‐Optical Fiber Configuration

Abstract

A crossed-optical-fiber configuration comprised of silver nanoparticles covalently attached to the core of an optical fiber and labeled with luminescent ruthenium molecules is reported. A second optical fiber was placed at right angle of the fiber containing the nanoparticle/ruthenium, to form a fiber-fiber junction, and it was used to detect the luminescence from the ruthenium molecules bound to the first fiber. To employ the effect of metal-enhanced luminescence, the ruthenium complex was kept at an appropriate distance from the nanoparticles by polyelectrolyte spacer layers. For silver nanospheres, nanotriangles and nanorods and for spacer-layer thicknesses from 2–14 nm luminescence-enhancement factors were determined. A 27-fold luminescence enhancement was found when the ruthenium complex was placed 4 nm from silver nanotriangles. Finally, a calibration curve for the oxygen dependence of luminescence intensities and lifetimes of ruthenium complex is presented suggesting that the oxygen sensing capabilities of the nanoengineered-ruthenium complex are maintained.

Application of time-correlated single photon counting and stroboscopic detection methods with an evanescent-wave fibre-optic sensor for fluorescence-lifetime-based pH measurements

“…Lifetime-based sensing has been demonstrated with optical fibres using probes with luminescence lifetimes of 100 ns or more for monitoring temperature [12][13][14], glucose [15], oxygen [16,17] and pH [18]. We have made similar measurements in our laboratory with a ruthenium-based oxygen sensor using a fast digitizing oscilloscope [19,20]. However, we observed an interference when measuring luminescence lifetimes of 10 ns or less, which are common for most fluorophores.…”