Charge Selective Separation of Dyes and Flavonoids

The conductivity of mesoporous titania provides a unique opportunity to examine charge-based binding and release of solutes in high surface area thin films and membranes. The main objective of this project is to develop separation strategies for biomolecules using titania-coated membranes and supports with applied voltage. Mesoporous titania-coated thin films (approximately 100 nm thick with 7 nm diameter pores) were synthesized on the surface of a fluorine doped tin oxide (FTO) coated glass slides. Using an electrochemical workstation, a working electrode was attached to the surface of the titania-coated thin film to apply a positive/negative charge. The effect of applied voltage (magnitude and sign of voltage) on the adsorption and desorption of methylene blue (a model dye with positive charge), acid orange II (a model dye with negative charge, and quercetin (a flavonoid that strongly binds to titania) was examined. The positively-charged methylene blue exhibited adsorption when a negative voltage was applied and desorption when a positive voltage was applied. Quercetin bound to mesoporous titania, most likely due to chelation interactions, but did not demonstrate charge-based binding or release. Additionally, being able to modulate biofouling with applied voltage is also important. Biofouling was examined using BSA (bovine serum albumin) as a model protein. The outcomes of this work provide insight into the design of membranes that exploit new charge-based mechanisms for bio-separation.