Water stability of self-assembled peptide nanostructures for sequential formation of two-dimensional interstitial patterns on layered materials

Developing various morphologies and a stable nanostructure of self-assembled peptides on a two-dimensional substrate has played a key role for bioelectronics and biomedical applications. Here, the adsorption and self-assembled characters of two artificial peptides with opposite charges are investigated on graphite and MoS 2 surfaces. The ex situ atomic force microscopy (AFM) results show that their morphologies, ordering and stabilities on graphite and MoS 2 surfaces are different. The negatively charged peptides self-assembled into an ordered nanostructure on graphite surfaces with six-fold symmetry in a wide range of peptide concentrations. On MoS 2 surfaces, the peptide shows a morphology change from randomly orientated nanowires to ordered aligned nanowires as the peptide concentration decreases. On the other hand, the positively charged peptides formed a disordered structure such as wavy structures or aggregates on both substrates. The affinity constants of both peptides on graphite and MoS 2 were estimated using concentration-dependence experiments. The stability against water soaking was also examined for both peptides on graphite and MoS 2 . We found that negatively charged peptides have high affinity constants and stability on both substrates. The results suggest that the stability of self-assembled peptides could be determined by their affinity constants on the substrates. Finally, by using the negatively charged peptides as a stable molecular template, we have demonstrated a sequential self-assembly of two different peptides on a graphite surface. The peptides self-assembled first on the surface show an ability to maintain their nanostructures, and guide the self-assembly of secondary self-assembled peptides. Both of the self-assembled peptides show the same orientations and ordered structures on a graphite surface. These results will open a new door for the development of biosensors with multiple biological probes on a functional surface such as graphite or MoS 2 .