Photosensitized-Photoactive Materials and Methods for Making and Using the Same

Technology

This technology can be thought of as two materials regimes: the photoactive regime and the photosensitive regime. Where the photoactive regime is a material composition that has a suitable flat band potential that can induce photochemical reactions without biased potential, and the photosensitive regime is a dye that sufficiently anchors to the photoactive surface to shift the materials bandgap to a useful spectrum. In addition to TiO2 a wide range of photoactive materials have shown altered wettability upon UV light irradiation such as ZnO, SnO2­, WO3, V2O5, SrTiO3, CeO2, etc. Similarly, there are a number of possible photosensitizers or dyes for this technology including N3, Z907, Z907Na, N719, Z910, N621, K19, K59, etc. For each of these composition regimes there are a number of synthesis methods that can be used such as the sol-gel method, the hydrothermal method, aerosol deposition, spray pyrolysis, chemical vapor deposition, atomic layer deposition, electro-deposition, direct oxidation, magnetron sputtering, spincoating, dipcoating, anodic oxidation and templating. Using combinations of these synthesis methods allows amplification of the wettability switching via texturing the photoactive surface to contain nanotube arrays, inverse opal three-dimensional structures, nanorod arrays, and/or nanopores followed by coating the photoactive surface with the photosensitive dyes to shift the absorbance spectra to the more useful visible regime.

Problem Addressed

Photoactive materials, such as titanium dioxide (TiO­­2), have attracted significant attention due to their ability to switch wettability upon irradiation of UV light. However, the large band gap in these materials limits their ability to absorb light effectively. Although doping has been demonstrated as an effective solution to enhance the visible light-induced wettability switching of photoactive materials, doping typically demands harsh conditions including high temperature, high pressure or toxic chemical environments, which limits versatility in the fabrication process. This technology is a novel approach to switch the wettability of photoactive materials to be responsive in the visible spectral regime using dye sensitization. Upon visible light irradiation, the dye sensitized photoactive surfaces undergo hydrophobic or hydrophilic conversion in both air and oil environments.

Advantages

• Reduced toxicity in synthesis
• Increased tunability for specific applications