We developed a sensor system to detect contamination in extremely small amount of liquid sample. Detection method is based on absorption measurement using surface plasmon sensor with enhanced absorptionsensitivity. Calculated result shows that the absorption-sensitivity of the sensor is -720 times higher than that of ordinary transmission method and-46 times higher than that of atteunated-total-reflection method. The minimum amount necessary for the absorption measurement is 2.4 pl from the calculation. We suc-cessfully detected methylene blue of 4.5 pg in 30μL water using this system. We expect that this sensor system can also be applied to qualitative analysis of other liquid samples having very small quantity together with reagent.
Morphology of Langmuir-Blodgett (LB) films was observed by means of a surface plasmon microscope. Images obtained by the microscope were compared with those obtained by an epifluorescence microscope. An LB film prepared from didodecylphosphate containing 2-mol% octadecyl rhodamine B as a fluorescence probe was transferred onto a slide glass coated with gold. Dendrite-like crystals observed with the fluorescence microscope were also found in the surface plasmon image when the monomolecular film was transferred onto the gold substrate coated with a polyimide LB film. The dendrites were not formed in the LB film directly deposited on the gold surface.
Variation of the second-harmonic signal with the incidence angle is studied for a clean Si (111) surface. Theoretical investigation of second harmonic generation leads to formulas connecting the generated light intensities to the surface nonlinear susceptibility tensor. Four independent tensor components for the Si (111)-7×7 surface are successfully deter-mined from the angular-dependence data.
The laser multi-photon inoization technique has been applied to the highly sensitive detection on water surface. The detection limit of pyrenesulfonic acid was 1.1×10-9mol dm-3 (310 ppt).This result indicates that the photoionization technique is useful and sensitive even for a highly polar solvent such as water.