(a) Schematic of the SPR imaging system, composed of a flow cell, a glass slide coated with Au (50 nm), a PDMS prism, a red laser light source (650 nm peak wavelength), a 5× objective lens, a CCD camera, and a mechanical scanning component. (b) Photograph of the proposed SPR imaging system.
(a) Numerical simulation and experimental results of reflectance as a function of the incident angle using glass and PDMS prisms, respectively. Compared to the results using a glass prism, the PDMS prism based setup produced a deeper but wider absorption peak with a higher coupling angle. (b) Collected SPR image with an array of 100 μm air cavities.
(a) SPR image of two-channel flow cell where one channel was used for sample detection (green) and the other one (red) as reference. (b) SPR results for the detection of helium and air. In cycles I and III, during the loading of the air, there was an intentional flow rate variation, leading to small peaks of RU at 2300 s and 4200 s, respectively.
SPR measurement results of nitrogen (RU) as a function of the flow rate from 0 to 800 μl/min. As the flow rate was increased, there was a recorded increase in RU first, which peaked at the flow rate of 100 μl/min, followed by a decrease of RU with further increase in the flow rate. Since the incident angle was fixed at the right side of SPR absorption peak, the measured RU value was inversely proportional to the RI value.
(a) Preliminary SPR measurement results of five different kinds of gas at a flow rate of 5 μl/min. Detection of oxygen and nitrogen was repeated twice, confirming the repeatability of the measurement results. (b) Plot of ΔRU as a function of Δn for measured nitrogen, air, oxygen, hydrogen, and helium with a calculated slope of 2 × 106 RU/n and a linear coefficient of 0.993 based on curve fitting.
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