Figure 2: Chemical and structural analysis of the peptide film.

(a) AFM image showing that multiple nanosheets are stacked (20 min assembly, Z-range: 10 nm). (b) The plot of the thickening of a film as a function of assembly time. The error bars represent the standard deviations of the means of five independent determinations from two separate experiments. (c) Changes in the surface pressure with varying peptide concentration. The surface pressure at different concentrations was used with the saturated surface pressure shown in the surface pressure versus time plot (Supplementary Fig. 31a). The experimental data show a close fit to the Langmuir and Frumkin isotherm models. The Frumkin isotherm model (R²=0.998) fits better than the Langmuir isotherm model (R²=0.966). (d) Raman spectra of monomeric peptides (black line) and films (blue line). Tyrosine peaks are indicated with a star (*). The peak at 503 and 2,568 cm⁻¹ indicates disulphide (–S–S–) and sulfhydryl (–SH) group, respectively. The Raman signal over the range of 460–540 cm⁻¹ is enlarged (inset).