Can you describe the role of layered silicates in more detail?
Zöllmer: Many studies try to incorporate these photocatalysts – without layered silicates – into coating systems and other surface coatings to degrade bacteria/viruses or other contaminants or toxins.
If a photocatalysis is to take place, meaning sunlight hits a titanium dioxide particle, degradation occurs when so-called radicals are initiated. Radicals are formed in the presence of water or moisture. Technically speaking, photocatalysis doesn’t take place without the presence of moisture. Applied to the pandemic, this mechanism factors in when it comes to aerosols as the viruses are transported via the moisture in the air we breathe.
The benefit of layered silicates like the phyllosilicates found in cat litter or clay pebbles as a substrate for potting soil, is that they absorb water or moisture. In the case of our polyurethane coating, they bring viruses/bacteria more effectively into contact with the titanium dioxide and accelerate the photocatalytic degradation rate.
Schreiner: Here’s the caveat: The photocatalyst decomposes organic matter. A common binder, meaning the film forming component of the coating, is an organic polymer. It obviously has a different chemical structure than a bacterium, but both are essentially organic matter.
In contrast, phyllosilicates are inorganic materials. To recap: The phyllosilicates enable our material to come into more effective contact with the bacteria/viruses slated for decomposition, while simultaneously protecting the coating from degradation.
If you didn't have these – I like to call them protective layered silicates -, the coating would be degraded with the same probability as the viruses/bacteria. Consequently, certain protective effects of the coating would fall away. Our combination approach has succeeded in maintaining an equilibrium between catalytic activity sustainment and simultaneous organic matrix protection.