Stitching together a nm thick peptide-based semiconductor sheet using UV light

Langmuir monolayer allows for two-dimensional nano-scale organisation of amphiphilic molecules. We here report that two retro-isomers peptides carefully designed to form stable monolayers showed semiconductor-like behaviour. Both exhibit the same hydrophobicity and surface stability but differ in the lateral conductivity and current-voltage due to the asymmetric peptide bond backbone orientation at the interface. The two peptides contain several tyrosines that allow for UVB-induced lateral crosslinking of tyrosines in neighboring peptide molecules. UVB-light induces changes in the lateral conductivity and current-voltage behaviour as well as monolayer heterogeneity monitored by Brewster angle microscopy that depends on the peptide bond backbone orientation and crosslinking of tyrosines. Our results indicate that one may design extended nano-sheets with particular electric properties, reminiscent of semiconductors. We propose to exploit such properties for biosensing and neural interfaces.