| New approaches on the design of fluorometric and surface plasmonic transducers for biosensor applications were explored in this work.;Surface plasmon resonance (SPR) studies focused on a relatively new approach where an intermediate dielectric layer was interposed between the coupling optics and the metal film of an SPR sensor with angular interrogation. We studied four simple dielectrics including MgF2 MgO, SiO2, TiO2 and six complex oxides in the PZT (Pb[ZrxTi 1-x]O3) family. The materials covered a wide range of refractive indices from 1.19 for the porous silica film to 2.83 for the TiO2 film. As expected, the intermediate dielectric layer had only a weak effect on the resonance for films with refractive indices close to that of the prism. The resonance sharpened dramatically for the ultra-low index, 1.19, porous silica film and narrowed as well for the high indices TiO2 and PLZT (La doped PZT) films when an air analyte medium was used. Published studies of the mode structure of surface plasmon waves suggested that the narrowing of the porous silica case was due to the near-equality of the indices of refraction, 1.19 and 1.00, on the two sides of the metal film, which favors the excitation of symmetric long-range surface plasmon. A narrow resonance is generally associated with reduced limit of detection.;The fluorometer was designed for transmission readout of a 1 mm 2 detector surface in a 2.4 muL micro-fluidic flow cell. A high performance fluorometer was constructed using an ellipsoidal reflector to focus the fluorescent light onto a compact photo-multiplier tube. A linear relationship between the concentration of fluorescent dye in the cell and photo-multiplier output was achieved over two decades from 2-200 nanomolar with an extremely high correlation coefficient. The 3-sigma concentration detection limit was 5 nanomolar. The surface concentration of fluorescent molecules was 2.5x1011 molecules/cm2. The device was also an efficient detector of scattered light. |
