Gold-Silver Alloy Film Based Colorful SPR Imaging Sensor with High Sensitivity for Quantitative Chemical and Biological Detection

Abstract

A gold-silver alloy film based spectral surface plasmon resonance imaging (SPRi) sensor has been prepared for in-situ quantitative detection of biochemical analytes at the sensor surface. This novel sensor has lower detection cost yet higher sensitivity relative to the conventional counterpart with a gold film. Using the laboratory-made multifunctional SPR sensing platform, both the resonant color images and the resonant spectra for the Au-Ag alloy film were measured at different incident angles. The quantitative relationship between the resonant wavelength and the average hue of corresponding resonant color image was established. With this relationship the most hue-sensitive spectral range was determined. After setting the initial resonant wavelength in the hue-sensitive spectral range, the refractive-index sensitivity of the Au-Ag alloy film based SPRi sensor was measured as Δhue/Δnc = 29,879/RIU, being 8 times higher than that obtained with the gold-film SPRi sensor. The immunodetection of benzo(a)pyrene (BaP) in water was fulfilled using the Au-Ag alloy film based SPRi sensor. The average hue of the SPR color image linearly increases with increasing the BaP concentration up to C = 0.5 μg/L and the slope is Δhue/ΔC = 132.2/(μg/L). The sensor is responsive to a change of BaP concentration as low as ΔC = 0.01 μg/L.

Keywords

• gold-silver alloy film
• SPRi
• quantitative detection
• high sensitivity
• color image
• hue