Publications Repository - Gdańsk University of Technology

Semiconductor|melanin interfaces have received increasingly more attention in the fields of photocatalysis and applied electrochemistry because of their facile synthesis, unique electrical properties, and strong capability toward photosensitization. In this work, we describe the electropolymerization of quinone-rich polydopamine (PDA) on the surface of hydrogenated TiO2 nanotubes with enhanced photoactivity in the visible spectrum. PDA is deposited uniformly on the nanotube walls, and the chemical structures of the resulting PDA layer strongly depend on the pH of the supporting electrolyte. The film thickness varies in the range of 2–8 nm depending on the number of electropolymerization cycles. Optical and electrochemical experiments coupled with density functional theory simulations revealed strong evidence of a semimetallic character of the junction with a broad distribution of midgap surface states induced by PDA. As a result of the nanotube modification, a 20-fold increase in the photocurrent response is observed. Quantum efficiency measurements show that the enhancement occurs mainly at wavelengths between 500 and 550 nm. Additionally, nonlinear electrochemical impedance spectroscopy experiments strongly suggest that, in the TiO2|PDA junction, PDA behaves as a set of redox mediators distributed at the surface rather than as a semiconducting polymer. This concept might be crucial for understanding the electronic properties of semiconductor|melanin junctions.

Authors

• Adrian Olejnik link open in new tab ,
• Karol Olbryś,
• dr hab. inż. Jakub Karczewski link open in new tab ,
• dr hab. inż. Jacek Ryl link open in new tab ,
• dr hab. inż. Robert Bogdanowicz link open in new tab ,
• dr hab. inż. Katarzyna Siuzdak