ABSTRACT
A two-dimensional phase-detection system for a surface-plasmon-resonance sensor is presented. The sensor utilizes polarization interferometry to detect phase differences between the s and p polarizations. We successfully detected a spatial phase-difference variation, resulting from the biomolecular interactions, of less than 1 x 1 mm(2). The phase stability demonstrated in the experimental results was approximately 0.09 degrees, and the corresponding change in the refractive index detection limit was approximately 4.3 x 10(-6). The common-optical-path configuration of the proposed method allowed us to reduce disturbances from ambient conditions. Furthermore, this method is capable of real-time array detection.
Subject(s)
Image Enhancement/instrumentation , Microscopy, Interference/instrumentation , Microscopy, Polarization/instrumentation , Surface Plasmon Resonance/instrumentation , Equipment Design , Equipment Failure Analysis , Image Enhancement/methods , Microscopy, Interference/methods , Microscopy, Polarization/methods , Reproducibility of Results , Sensitivity and Specificity , Surface Plasmon Resonance/methodsABSTRACT
In this study, the design of a novel optical sensor that comprises surface plasmon resonance sensing chip and zinc oxide nano-film was proposed for the detection of nitric oxide gas. The electrical and optical properties of zinc oxide film vary in the presence of nitric oxide. This effect was utilized to prepare biochemical sensors with transduction based on surface plasmon resonance. Due to the refractive index of the transparent zinc oxide film that was deposited on the gold film, however, changes will be observed in the surface plasmon resonance spectra. For this reason, the thickness of zinc oxide film will be investigated and determined in this study. The interaction of nitric oxide with a 20 nm zinc oxide layer on gold leads to the shift of the resonance angle. The analysis on the reflectance intensity of light demonstrates that such effect is caused by the variation of conductivity and permittivity of zinc oxide film. Finally, a shift in surface plasmon resonance angle was measured in 25 ppm nitric oxide at 180 C and a calibration curve of nitride oxide concentration versus response intensity was successfully obtained in the range of 250 to 1000 ppm nitric oxide at lower temperature of 150 C. Moreover, these effects are quasi-reversible.
