| Surface plasmon resonance (SPR) sensors are optic ally-interfaced devices that detect the refractive index of a thin layer of analyte in contact with the sensor surface. For biosensing applications such as food toxin or biological warfare agent detection, high-resolution detection of the target species provides an improvement in the detection limit of the SPR sensor.; We present the design, modeling, and implementation of an improved SPR biosensor based on long-range surface plasma wave (LRSPW) spectroscopy. An LRSPW consists of two surface plasma waves coupled across a thin metal layer. The LRSPW has lower attenuation than a single surface plasma wave, producing a narrower absorption minimum in the sensor spectral response. This narrower minimum results in improved resolution due to reduced uncertainty in the position of the minimum.; Theoretical design curves presented for an LRSPW sensor using a Teflon AF buffer layer and gold metal layer show that the sensor can have sensitivity as high as 1 × 105 nm RIU−1, an order of magnitude or more improvement over conventional SPR sensors. Results of a biosensing experiment conducted with the LRSPW sensor showed a resonance width of only 15 nm (full-width at half-minimum), a sensitivity of 3.1 × 104 nm RIU−1, and a corresponding resolution of 1.9 × 10−7 RIU. Compared with a similar experiment conducted using a conventional SPR sensor, the LRSPW sensor had 25 times better resolution.; To further improve the resolution of SPR sensor systems, we also present methods for evaluating the performance of data-processing algorithms for analyzing SPR spectra, including a method for predicting the instrument resolution based on measured system and detector noise. A new interpolated tracking centroid data-processing algorithm is presented, and its performance in terms of resolution, linearity, and resistance to environmental drift is shown to be superior to that of a simple centroid algorithm. |
