Revealing the structure of bioinspired polydopamine (PDA) surfaces
Physical Chemistry of Solids and Surfaces, Material Characterisation
Final Report Abstract
We presented infrared spectroscopic measurements which allow to in situ monitor the growth of thin PDA films with thickness from 6 nm to 25 nm. Spectral and optical layer model interpretations enabled an investigation of the chemical and molecular structure of the prepared layer. Even though we cannot reveal an exact average molecular structure of the prepared PDA films, the in situ and ex situ IR, XPS results of PDA showed: a) small amount of C55O groups exist in the PDA film prepared in Tris buffer; b) from oxidation it can be concluded that some OH groups must be also imbedded in the PDA film pointing to a significant amount of PDA in dihydroxyindole structure. The AFM-IR results showed a granular topography of the PDA surface. Meanwhile, the AFM-IR results also revealed for the probed area in the flat region a chemically similar PDA film at the nano-scale. The in situ IR monitoring of the Michael addition reaction shows the possibility of immobilization of thiol-terminated/inclusive (or cysteine-modified) biomolecules on the PDA surfaces, which could be applied to build biosensors with this material in the future. The addition of Fe3+ ions in PDA solution is catalysis-like effect, while the Cu2+ ions is co-existed in the final PDA film based on the IRSE and XPS results. The PDA films prepared with Fe3+ and Cu2+ are easy to be oxidized in the air compared to the film without the addition of the ions. More work need to be done to study the polymerization process and the final precise structure of PDA prepared in different conditions (e.g., replace the buffer solution with oxidative metal ions, other oxidative chemical reagents or UV illumination, in acid solution…) and new technologies/methods should be applied in the research, such as using DFT simulation.
Publications
- ‘In-situ Monitoring of the Electrochemical Surface Modification by Thin Organic Layers’, Chapter 6 in ‘Advanced Green Chemistry - Part1: Greener Organic Reactions And Processes’, I. T Horváth and M. Malacria (Eds.,), 2018, World Scientific Publishing Co. Pte Ltd.
J. Rappich, G. G. Sun, K. Hinrichs
(See online at https://doi.org/10.1142/9789813228115_0006) - In Situ Infrared Spectroscopic Monitoring and Characterization of the Growth of Polydopamine (PDA) Films. Phys. Status Solidi B. 2019, 1800308
G. G. Sun, F. S. Zu, N. Koch, J. Rappich, and K. Hinrichs
(See online at https://doi.org/10.1002/pssb.201800308)
