Researchers Develop Highly Stable Self-Cleaning Paints

Researchers from TU Wien and the Università Politecnica delle Marche (Italy) have created unique titanium oxide nanoparticles that can be added to standard, commercially available wall paint to provide self-cleaning properties. The nanoparticles are photocatalytically active, meaning they can utilize sunlight to bind substances in the air and decompose them.

Qaisar Maqbool and Günther Rupprechter. Image Credit: Vienna University of Technology
Qaisar Maqbool and Günther Rupprechter. Image Credit: Vienna University of Technology

The wall purifies the air while simultaneously cleaning itself. Waste, including metal waste and dried fallen leaves, was employed as the raw material for the new wall paint.

Modified Titanium Oxide in the Wall Paint

Indoor air contains a wide range of contaminants, including cleaning agents, hygiene product residues, and molecules created during cooking or exhaled by materials like leather. This might sometimes result in health problems, a condition known as “sick building syndrome.”

For years, people have been trying to use customized wall paints to clean the air. Titanium oxide nanoparticles are particularly interesting in this context. They can bind and break down a wide range of pollutants.

Günther Rupprechter, Professor, Institute of Materials Chemistry, Vienna University of Technology

However, just adding conventional titanium oxide nanoparticles to the paint can impact its durability: the nanoparticles break down contaminants, making the paint unstable and causing cracks. In the worst-case scenario, volatile organic chemicals could be emitted, posing health risks. The paint layer eventually turns gray and colored, necessitating a renewal.

Self-Cleaning by Light

However, when exposed to ultraviolet (UV) light, nanoparticles can clean themselves. Titanium oxide is a photocatalyst, which is a material that allows chemical processes to occur when exposed to particular types of light. UV light produces free charge carriers in particles, causing stored contaminants from the air to decompose into tiny components and be released.

As a result, the contaminants are harmless yet are not permanently bonded to the wall paint. In the long run, the wall color remains stable.

In reality, however, this is ineffective; after all, continually irradiating the wall with powerful UV light to drive the self-cleaning process would be time-consuming.

Our goal was therefore to modify these particles in such a way that the photocatalytic effect can also be induced by ordinary sunlight,” Rupprechter added.

This is accomplished by incorporating extra atoms such as phosphorus, nitrogen, and carbon into titanium oxide nanoparticles. As a result, the light frequencies that the particles can harvest alter, and photocatalysis is now activated by visible light and ultraviolet (UV) light.

96% Pollutant Removal

We have now investigated this phenomenon in great detail using a variety of different surface and nanoparticle analysis methods. In this way, we were able to show exactly how these particles behave, before and after they were added to the wall paint.

Qaisar Maqbool, Study First Author and Postdoctoral Scientist, Vienna University of Technology

The researchers merged the modified titanium oxide nanoparticles with standard, commercially available wall paint and rinsed the painted surface with a pollutant-containing solution. As a result, natural sunlight can potentially destroy 96% of contaminants. The color remains constant because the contaminants are bound and broken down by sunlight.

Waste as a Raw Material

It is also critical to avoid using expensive raw materials for these paints to be a commercial success.

Rupprechter stated, “In catalysis, for example, precious metals such as platinum or gold are used. In our case, however, elements that are readily available from everywhere are sufficient: To obtain phosphorus, nitrogen and carbon, we have used dried fallen leaves from olive trees, and the titanium for the titanium oxide nanoparticles was obtained from metal waste, which is normally simply thrown away.

The new type of wall paint has many benefits at the same time: it cleans the air of pollutants, it lasts longer than conventional paints, and because it can be made from recycled materials, it uses even fewer resources during production. More studies are being conducted, and commercialization of the wall paint is intended.

Journal Reference:

Maqbool, Q., et. al. (2024) Highly Stable Self-Cleaning Paints Based on Waste-Valorized PNC-Doped TiO2 Nanoparticles. ACS Catalysis. doi:10.1021/acscatal.3c06203


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