Figure 2

Optical characterization of Reflectin films. (a–f) Films with various thicknesses (1 µm (a), 2.5 µm (b), 12 µm (c), 0.5 µm (d), 1 µm (e) and 5 µm (f)) generated by spin coating of Reflectin (SoRef2) incubated with and without imidazole on glasses, labeled as R/I (Reflectin/Imidazole) and R (Reflectin), respectively. All the pictures were obtained against black background (upper half) with a white background (lower half) underneath. Reflectin with imidazole (R/I) films appear blue on a black background and light yellow on a white background, respectively (a–c). In contrast, reflectin films without imidazole (R) are colorless (d–f). (g,h) Spin-coated films (4 µm) of BSA incubated with (g) and without (h) imidazole, labeled as BSA/I and BSA, respectively. Both films are colorless. i, Schematic of setup for transmittance measurement used in this work. (j) Transmittance spectra of Reflectin and BSA films in (a–h) measured with the setup used in (i). (k) Schematic of setup for specular reflectance measurement used in this work. Both the angles of incident and observation light are from the normal direction. (l) Normalized specular reflectance spectra of Reflectin and BSA films in (a–h) measured with the setup used in (k). (m) Schematic of setup for scattered light measurement. The incident angle is 45°, and the observation angle is 0° (normal direction). (n) Normalized scattered reflectance spectra of Reflectin and BSA films in (a–h) measured with the setup used in (m). (o) Schematic of setup used for scattered reflectance measurement of R/I and R films in (c) and (f) under different incident angles. Angle of incident light can be changed (25°, 35°, 45°, 55°, 65°) with the rotation of light source fiber, whereas the detector remains at the normal direction. (p) Normalized scattered reflectance spectra of R/I and R films in (c) and (f) under different incident angles measured with the setup used in (o). (q) Schematic of setup used for scattered reflectance measurement of R/I and R films in (c) and (f) under different observation angles. The light source fiber remains at the normal direction, whereas the angle of observation can be changed (25°, 35°, 45°, 55°, 65°) with the rotation of the detector fiber. (r) Normalized scattered reflectance spectra of R/I and R films in (c) and (f) under different observation angles measured with the setup reported in (q). The scale bars represent 2 mm.