Antimicrobial coatings for the reduction of airborne pathogens

Photocatalytic antimicrobial coatings rapidly kill pathogens in their vicinity when exposed to the correct wavelengths of light. Key advantages of photocatalytic antimicrobials are their very long life, lack of requirement for any additional chemicals, and safety. They are therefore an extremely useful tool for limiting the spread of infectious diseases. There are a wide variety of photocatalytic materials, including silver, copper and zinc oxide, but one of the most commonly studied and utilised material is titanium dioxide (TiO2) due to its effectiveness, ease of coating, and low cost. TiO2 is already used in applications such as anti-microbial paints and fabrics, and self-cleaning glass.

Conventional photcatalysts, including TiO2, do have some disadvantages, however. Firstly, to obtain high efficiencies very high surface areas are needed, which is often difficult to achieve using conventional coating approaches. Secondly, usually very specific wavelengths of light, typically in the UV region, are needed to activate the photocatalyst, meaning that special light sources or other devices are required for indoor use. What is needed is a rapid, low cost, and scalable approach to forming ultra-high porosity photocatalyts with wide spectrum (i.e. including visible light) activation.

Keronite has been using its proprietary plasma electrolytic oxidation (PEO) technology for many years to produce oxide coatings on light metals. When deployed on Ti alloys, the surface of the alloy is converted predominately to active photocatalytic TiO2. A great advantage of the PEO process is that the coatings formed are inherently porous. Further, by altering the electrical parameters of the process, the porosity can be controlled. We have shown that it is possible to form extremely porous structures on TiO2 with pore sizes ranging from micrometers to the nanometers. We have shown that the coatings are highly photoactive. Indeed, the recent highly successful Innovate UK supported "Pristine" project demonstrated a 10-fold improvement in the efficiency of removal of contaminants such as glycols from water.

The proposed projects seeks to enhance and deploy this technology for the destruction of airborne pathogens under ambient indoor conditions. To do so we propose further developing the PEO approach to form ultra-high surface area TiO2 "scaffolds" which also incorporate other active species (e.g. silver) to form a high activity, broad light-spectrum anti-microbial surface. The program targets rapid deployment of the technology with partners and downstream users and includes a significant element of value chain engagement.

- ADDITIONAL INFORMATION - Extended Project
Work in the first phase of the project has identified a number of promising routes for producing highly active “doped” photocatalysts that show good absorption in both the visible and UV parts of the spectrum. The extended project enables us to build on these initial results in three main ways:

1. It allows a greater variety of coating options to be explored/tested – There are a very large number of options we are exploring, including incorporation of elements such as Ag, Cu, Zn, N, F, P etc. The extended project will allow us to explore a larger variety of these options in greater depth.

2. Extended biocidal testing – Ultimately this project is about proving the antibacterial/antiviral performance of the coatings The cost of this testing is high and the tests are time consuming. An expanded project allows us to do much more, and will enable us to produce a convincing portfolio of results we can use to drive and accelerate our exploitation efforts.

3. Extend the range of substrate types – Commercial partners have expressed strong interest in our TiO2 coatings on a range of different metal substrates. The extended project will allow us to increase our efforts in this regard and will accelerate the process of proving the effectiveness of the approaches we are exploring.