Fig. 1: SFG spectral characteristics of assemblies in the amide region.
a The molecular structures of L-/D-GAn and Fmoc-Glu-C18. The sequence numbers (1, 2, 3) represent three amide bonds in different positions of the molecule, and * indicates the asymmetric carbon atom. b SFG energy level diagram. Energy level code: Virtual (virtual electronic state), ν = 1 (vibrational state), ν = 0 (ground state). c A schematic representation of the psp chiral polarization setting to detect the chiral supramolecular monolayer formed by the self-assembly of L-/D-GAn molecules at the interface. (The projection of the electric field of p-polarized and s-polarized light onto the laboratory coordinates (XYZ).) SFG-VS spectra were recorded using achiral ssp, sps, ppp polarization, and chiral psp polarization for d D-GAn and f Fmoc-Glu-C18 monolayers at a surface pressure of 40 mN/m at the air/water interface. The positions of the three amide peaks in the spectra of the L-/D-GAn molecule (dashed lines) can be clearly assigned by analyzing the amide regions of the spectra of three molecules with similar structures. The chiral SFG-VS was recorded using e psp and g s(+m)p-s(-m)p polarization for the L-GAn and D-GAn monolayers at different surface pressures at the interface. The assemblies of the L-GAn and D-GAn molecules formed opposite supramolecular chirality at the interface. The fitting results are listed in Supplementary Tables 1−4.
