Role of the interfaces and the charge of a molecule in the non-equilibrium crystallization of dipeptide nanomaterials onto solid substrates

Abstract

The influences of various factors on the processes of the non-equilibrium crystallization of short dipeptides from aqueous solutions were studied. Non-equilibrium crystallization leads to the formation of spatially heterogeneous structures. Depending on the charge of the peptide molecule (neutral or anion), not only does the surface morphology of the solid layers change, but also their electron energy and chemical structures change. The net charge of the molecules also affects their self-assembly and the growth of mesocrystals. An important role is played by the properties of the substrate–layer interfaces, which are responsible for the growth mechanism and formation of ferroelectrics on gold. In thin DPT layers, the structure of the first adsorption layer is a template for the growth of all subsequent layers and determines the growth mechanism, even at layer thicknesses of several hundred nanometers. The structure of the solid layers significantly depends on the charges on the substrate surface, which can polarize peptide molecules or compensate for the charges of individual functional groups in them. On the graphite surface, the 2D growth of DPT monolayers (layer-by-layer), while on gold and mica surfaces, the 3D growth of individual aggregates is observed. Bipolar resistive switching in thin peptide layers on graphite and gold surfaces was found. By varying the pH of the solution (the charge of the peptide molecule), it was possible to control the structure and properties of the crystallized layers. The obtained results can find practical applications in 3D printing technologies, as a perspective functional material of memristor organic electronics, and in the pharmaceutical industry.