Fig. 1. Schematic diagram of the Kretschmann-type surface plasmon resonance sensor’s measurement principle

Fig. 2. Framework diagram of the testing scheme for the Kretschmann-type sensor

Fig. 3. UV-Vis absorption spectra of TiO₂/PSS multilayer films in air. The inset picture is the absorbance intensity at 250 nm v.s. the number of bilayers

Fig. 4. Reflected light intensity spectra of sensors with different bilayers of TiO₂/PSS films: in water (a) n = 1−5, (c) n = 9−19, (e) n = 21−36; in air (b) n = 1−5, (d) n = 12−25, (f) n = 28−48

Fig. 5. Absorption spectra of sensors assembled with different bilayer TiO₂/PSS films in both water and air. (a) n = 1−5, (b) n = 9−19 , (c) n = 20−34, (d) n = 35−48

Fig. 6. The relationship between the resonance wavelength in the reflectance spectrum and the number of TiO₂/PSS film bilayers. (a) In water a: n = 0−1, b: n = 9−19, c: n = 20−34, d: n = 35−48; b: in air e: n = 1−5, f: n = 11−19, g: n = 25−34, h: n = 38−48

Fig. 7. The relationship between the film thickness and transverse magnetic field mode distribution. (a) 100-nm thick film in water, (b) 300-nm thick film in water, (c) 400-nm thick film in air, (d) 600-nm thick film in water, (e) 1000-nm thick film in water