Fig. 4.

CEIRA signal of silk films. (A) Silk film thickness is measured by atomic force microscope for a 4 nm thick film. (B) Amide-I and II vibrational modes of the protein back bone. (C) Reflectance spectra from the 1.6 μm periodic array before (dashed line) and after coating of 2 nm thick protein film (solid line). Dashed vertical lines indicate the positions of the protein amide-I and II absorption peaks. (D) Difference absorption spectra of the arrays whose spectral characteristics before protein coating are given in Fig. 3B.