Resolution Enhancement in Surface Plasmon Resonance Sensor Based on Waveguide Coupled Mode by Combining a Bimetallic Approach

In this study, we present and demonstrate a new route to a great enhancement in resolution of surface plasmon resonance sensors. Basically, our approach combines a waveguide coupled plasmonic mode and a kind of Au/Ag bimetallic enhancement concept. Theoretical modeling was carried out by solving Fresnel equations for the multilayer stack of prism/Ag inner-metal layer/dielectric waveguide/Au outer-metal layer. The inner Ag layer couples incident light to a guided wave and makes more fields effectively concentrated on the outer Au surface. A substantial enhancement in resolution was experimentally verified for the model stack using a ZnS-SiO2 waveguide layer

Bimetallic Layers Increase Sensitivity of Affinity Sensors Based on Surface Plasmon Resonance

Two metals are used in resonant layers for chemical sensors based on surface plasmon resonance (SPR) - gold and silver. Gold displays higher shift of the resonance angle to changes of ambient refraction index and is chemically stable. Silver posses narrower resonance curve thus providing a higher signal/noise ratio of SPR chemical sensors, but has a poor chemical stability. A new structure of resonant metallic film based on bimetallic silver/gold layers (gold as an outer layer) is suggested. It combines advantages of both gold and silver resonant layers. Bimetallic resonant films display so high shift of resonance angle on changes of ambient refraction index as gold films, but show narrower resonance curve, thus providing a higher signal / noise ratio. Additionally, the outer gold layer protects silver against oxidation

Surface enhanced infrared absorption of nucleic acids on gold substrate

Data on surface enhanced infrared absorption (SEIRA) of nucleic acids deposited on the metal surface have been obtained in the experiment in FTIR reflectance mode. As metal surface, we used Au of 200-500 Е thickness on glass substrate. Roughness of Au was about 50 Е. In our experimental conditions, the enhancement factor of SEIRA was 3 to 5. We obtained different enhancement factors for different vibrations of nucleic acids. Application of this method to tumour nucleic acid gave a possibility to reveal some structural peculiarities of their sugar-phosphate backbone and those after application of anti-cancer drugs