q&more
My watch list
my.chemie.de  
Login  

News

Clean through solar power

peternguyen11, pixabay.com, CC0

03-Aug-2018: In combination with the right materials, sunbeams can work wonders: they clean building facades and decompose pollutants from the air or in the water. The magic word is photocatalysis. In practice, though, the effectiveness of this „miracle cure“ fluctuates greatly, depending on the material used and the environmental factors. With a new measuring device, researchers now want to determine the photocatalytic effectiveness of surfaces more accurately and quickly, thereby increasing efficiency.

Driving bans, diesel retrofitting or the blue badge – there is currently a lot of discussion about how to reduce nitrogen oxide and particulate matter in cities. How practical would it be if house facades and roofs would simply clean the city air in passing? And if buildings could free themselves of dirt right away? The good news is that this is already possible with photocatalysis. When building materials are mixed with a so-called catalyst such as titanium dioxide (TiO2), sunlight in combination with oxygen triggers a chemical reaction. The titanium dioxide forms reactive substances that decrease dirt and pollutants. Whether concrete, glass or facade paint, almost every material can be upgraded with photocatalytic technology.

There are several pitfalls, though: depending on the substrate, surface structure and environmental influences, the photocatalytic efficiency varies by up to 100 percent or more, depending on the pollutant and product. The effectiveness is also a matter of the right mixture: if only the surface is coated, the catalyst quickly washes off or erodes. If you mix it into the material, much of it is not effective. The optimum mixture has not yet been found. Moreover, the long-term behavior and stability of such building materials are difficult to predict outside of the laboratory.

Moreover, there is a high discrepancy between the efficiencies which are achievable in the laboratory and those obtained outside in practical use. These issues have barely been studied yet. A better understanding of these relationships was the goal of the eleven partners in the joint project PureBau. Their goal was to improve the efficiency of material compounds so that better photocatalytically active building materials can be developed.

A new tool for efficient research

As one of the partners, the Fraunhofer Institute for Surface Engineering and Thin Films IST in Braunschweig is working on a measuring method that makes this very thing possible. "The previous research and development of photocatalytically active building materials was often a trial-and-error process, due to the lack of a suitable measurement procedure. In addition, it was simply not possible to perform reliable measurements in the field. Although effects can be calculated using simulation, this process is laborious and, in addition to that, it’s not widely used", says Frank Neumann, Head of Working Group Photocatalysis at the Fraunhofer IST.

Neumann and his colleagues had already patented a process to quickly and reproducibly measure the photocatalytic self-cleaning of products on a laboratory scale. This enables a determination of how quickly a material with a certain catalyst cleans a surface, such as a facade or a tiled roof. The basic principle: a luminescent dye is vapor-deposited onto a surface, and then the speed at which it fades under the influence of light is measured. From the parameters of light intensity and thickness of the dye layer, the efficiency can be determined.

From the laboratory to the field

The challenge now was to transfer this method to a portable device that works without vacuum conditions, while significantly accelerating the measurement. Through their collaboration with the Institute for High Frequency Technology (IHF) of the Technical University of Braunschweig, the researchers achieved this in two steps: since the dye synthesis that was used in the laboratory up until then displayed too many unwanted chemical reactions, they had to find new dyes. Dyes with europium-metal complexes were used, just like in OLEDs. In addition, the previous method of vapor depositing no longer worked for the mobile application. "Instead, we transferred the dyes in a mono-layer to a polymeric carrier and chemically combined both by means of so-called anchor groups," Neumann explains. The backing film has the advantages of being well-suited to any surface, minimizing chemical reactions with the material and avoiding damage caused by measurements made directly on facades (e.g., dye transfer). The coating with a single layer of dye ensures the reproducibility of the process.

In the next step, a demonstrator of a mobile measuring gun was developed together with the company Omicron Laserage Laserprodukte GmbH. In a bayonet lock, the film is attached there with the dye coating and pressed onto the surface which is to be tested. The device then measures the decay of luminescence by the UV irradiation and determines the photocatalytic effectiveness – both qualitatively as well as quantitatively by the degree of efficiency. The measurement time in this procedure has been reduced to about 15 minutes, compared to relevant standard testing which can last up to three hours.

Neumann is confident that the measurement technique could be ready for the market in one to two years. This would be interesting for building material manufacturers, coating experts and measuring  service providers, as well as for users: "Above all, it would finally be possible to control the quality of currently used products in the field, but it would also be possible to accelerate the development of effective photocatalytic materials". In the long term, this in turn could promote the extensive self-cleaning of facades, roofs and traffic routes and ensure a better climate in our cities.

Facts, background information, dossiers

More about Fraunhofer-Institut IST

  • News

    Precisely fitting bone implants from the printer

    Cancerous tumors, infections or bad fractures can make it necessary to surgically remove bones and insert implants in their place. In collaboration with European partners, Fraunhofer researchers have now developed a technique with which bone implants that are precisely fitting, stable and v ... more

More about Fraunhofer-Gesellschaft

  • News

    Fraunhofer presents high-speed microscope with intuitive gesture control

    The Fraunhofer Institute for Production Technology IPT in Aachen has developed a high-speed microscope for quality control of large-area objects for the semiconductor and electronics industries or for rapid testing of biological samples. The microscope digitizes samples with up to 500 frame ... more

    Pocket-size food scanner

    According to a study by the environmental organization WWF Germany, ten million metric tons of food are thrown in the garbage every year in Germany despite still being edible. A mobile food scanner will allow consumers and supermarket operators in the future to test whether food items have ... more

    Producing vaccines without the use of chemicals

    Producing vaccines is a tricky task – especially in the case of inactivated vaccines, in which pathogens must be killed without altering their structure. Until now, this task has generally involved the use of toxic chemicals. Now, however, an innovative new technology developed by Fraunhofe ... more

q&more – the networking platform for quality excellence in lab and process

The q&more concept is to increase the visibility of recent research and innovative solutions, and support the exchange of knowledge. In the broad spectrum of subjects covered, the focus is on achieving maximum quality in highly innovative sectors. As a modern knowledge platform, q&more offers market participants one-of-a-kind networking opportunities. Cutting-edge research is presented by authors of international repute. Attractively presented in a high-quality context, and published in German and English, the original articles introduce new concepts and highlight unconventional solution strategies.

> more about q&more

q&more is supported by:

 

Your browser is not current. Microsoft Internet Explorer 6.0 does not support some functions on Chemie.DE