Characteristic Adsorption of Amino Acids on Surface of Al₂O₃ (0001) Single Crystal in Water Solution

We have been interested in a study to control cellular configuration on various functional oxides as an immobilization substrate for cell adhesion protein. For this purpose, adsorption interaction of various amino acids to terrace, step and kink (surface nanostructures) on the atomically flat surface of functional oxides should be studied with atomic scale as a preliminary experiment.
In this study, we investigate the adsorption behaviors of glycine, phenylalanine and alanine by using atomic force microscope (AFM) on the surface of Al₂O₃ (0001) that surface annealed at 1100 °C (single-step) and 1400 °C (multi-step) in air for 3 hours. The AFM images were taken for Al₂O₃ (0001) surfaces in the ultra pure water, water solution of glycine, alanine and phenylalanine (10^-3 mol/l). From the AFM images, the specific adsorption of glycine can be found only for the multi-step surface. However, phenylalanine and alanine adsorbed even on the single-step surface while glycine did not.