Synthesis and Photoactivity of Bioinspired Titania-Based Membrane Systems

Titanium dioxide (titania) is an abundant, inexpensive material of interest for its photoresponsive, and electronic activity. Despite many existing applications of titania particles, its use in thin films and membranes is still developing. The overarching objective of this project is to develop titania membranes that are able to harness solar energy for useful applications including degradation of organic pollutants, generation of hydrogen from water, and photo-driven enzymatic reactions. This presentation will discuss several advances toward this goal. First, a bioinspired self-assembly approach will be described to synthesize thin films and membranes with accessible, uniformly sized ordered arrays of nanopores on the order of 8-10 nm in diameter. Second, tuning of the visible light absorption behavior of titania thin films will be discussed using plasma treatment to reduce its band gap by introducing nonmetals such as nitrogen. Such modification leads to very substantial increases in visible light photocatalytic activity (on the order of 6 times for organic pollutant degradation and over 200 times for photocatalytic water splitting) due to the ability to introduce highly reactive plasma species into the disordered framework of the freshly prepared nanoporous films. Finally, advances will be described towards the modification of the titania surface using dopamine and its polymers. (Poly)dopamine not only a combination of amine and catechol (dihydroxybenzene) groups that mimic mussel adhesive proteins, but also has been used as an anti-fouling modifier for polymeric membranes. Here, the catechol groups are specifically utilized as strong bidentate complexation binding sites with the titania surface. It is also found that (poly)dopamine forms a red material at the surface which absorbs visible light and therefore acts as a sensitizer for photocatalytic water splitting. We will discuss ongoing efforts to understand and improve the long-term stability of the poly(dopamine) coating.