Multispectral Refractive Index Sensing Using Surface Plasmon Resonance on Gold Nanoslits
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Multispectral Refractive Index Sensing Using Surface Plasmon Resonance on Gold Nanoslits Pei-Yu Chung1, Kuang-Li Lee2, Gregory Schulz3, Pei-Kuen Wei2, and Christopher Batich1 1 Department of Material Science and Engineering, University of Florida, Gainesville, FL, USA 2 Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan 3 Department of Obstetrics and Gynecology, University of Florida, Gainesville, FL, USA ABSTRACT Surface plasmon resonance (SPR) biosensors are widely used in sensitive chemical, biological and environmental sensing. Recently, the studies of nano-plasmonics in metallic structures have shown that surface plasmons can also be excited by the metallic nanostructures films which can be used for high-throughput and chip-based SPR type sensing. We developed a class of plasmonic crystal-like structures consisting of a film with arrays of periodic nanoslit geometry. Because the engineered array ensures multiple resonance modes, we use the multispectral analysis to evaluate the refractive index sensing capability. Different from the common method monitoring a single peak shift, the multispectral analysis, observing all the peak shifts and intensity changes in the multiple plasmonic resonances in the spectra, can improve the signal-to-noise ratio of the system and enhance the sensing capabilities. In this investigation, we studied the best condition for the gold nanoslit arrays by testing their ability for refractive index sensing, and a high sensitivity of up to 28586 %T·nm/RIU was obtained by multispectral analysis (RIU = refreactive index unit, and T= transmission).
INTRODUCTION The common SPR biosensors utilize the attenuated total internal reflection (ATR) method to excite surface plasmon resonance on a thin gold film coated on a prism, but a complicated system setup also comes with the prism based SPR biosensors. Surface plasmon polaritons (SPPs) generated in plasmonic crystals play an important role in a wide range of nanostructure plasmonic crystals and allow a label-free, high sensitivity, real-time and surface specific detection. This is especially as a diagnostic technique, and for use in drug discovery and proteomics research[1-3]. Although microarrays are promising tools to use for biomolecular studies, and surface plasmon resonance imaging (SPRi) can be exploited in the field of microarrays, the conventional method of monitoring a single peak or dip cannot reveal all the information lying in multi resonances in the spectra of plasmonic crystals, and thus limits the sensing capacity[4-8]. A multispectral analysis which monitors multispectral changes that include both the transmission and the wavelength changes in the spectra is more suitable for a simple imaging system[9]. Here, we present a class of plasmonic crystals, the gold nanoslit arrays which exploit small-dimension arrays (150 um X 150 um) and thus offer opportunities for high packing density of sensing elements and easy integration with microfludic devices[10, 11]. The measuring platform was built on an inv
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