Oriented crystal growth of phenylalanine and dipeptide by solution shearing
Self-assembled structures of peptides have been recently gaining fundamental interests due to its unique electrical and optical properties arise from their variety of nanostructures. One of the challenges in this field is a formation of oriented nanostructures on a substrate. For more practical electrical applications, It is crucial to form its thin film on a substrate without losing its intrinsic physical properties due to random orientation. Here, we developed a technique to form thin films of crystalized amino acid and dipeptide by solution shearing. We characterized the thin films by polarized Raman spectroscopy and X-ray diffraction (XRD) measurements. Raman spectra revealed that the solution shearing allows us to form crystalline amino acid and dipeptides on Si wafer with a control of its crystal orientation along to the direction of shearing. The XRD supported the result of Raman spectroscopy, and also revealed the preferred orientation of the crystals in the out-of-plane direction. Futhermore, their polymorph formation was found to be suppressed by the solution shearing. This new approach for the formation of aligned biomolecular thin film can be helpful for its bioelectronic applications in the future.