Benzo[a]pyrene sensing properties of surface plasmon resonance imaging sensor based on the hue algorithm

A colorful surface plasmon resonance imaging sensor for the in-situ detection of benzopyrene (BaP) in water is presented in this paper. The sensor can provide intuitive image information and can also quantitatively analyze the concentration and adsorption/desorption processes of the analyte by combining the hue algorithm. Both the resonance wavelengths and resonance images for a bare gold film chip were obtained at different incident angles using a home-made surface plasmon resonance (SPR) sensor that possesses wavelength-interrogating and imaging capabilities. The relationship between the resonance wavelength and the average hue of the color image was established based on the hue algorithm. From this relationship, the initial resonance wavelength at which the SPR sensor can provide optimal hue sensitivity was derived, which was ~650 nm. Polytetrafluoroethylene (PTFE)-coated SPR sensor chips were prepared for the in-situ rapid detection of BaP in water based on the reversible enrichment of BaP molecules in the PTFE film. The results showed that: (1) the average hue of the SPR color image decreases linearly as BaP concentration increases from 20 to 100 nmol·L⁻¹; (2) both the response time and recovery times of the SPR sensor for 100 nmol∙L⁻¹ BaP are 7 and 5 s, respectively; (3) since the thickness of the PTFE film is greater than the penetration depth of the surface plasmon field, the BaP detection is not affected by the refractive index of the solution sample; and (4) in the case of a non-uniform PTFE film, the sensor allows to determine the hue sensitivities for equal-thickness microscale areas of the sensing film. The experimental results show that this type of colorful SPR imaging sensor has widespread applicability for chemical and biological detection.