University of São Paulo: Researchers create new floor covering with self-cleaning properties

Researchers have created a new coating, based on titanium dioxide and silica compounds with self-cleaning properties, to be applied on ceramic floors. The material allows the floors, after having contact with light sources, to degrade dust, grease, drug residues and atmospheric pollutants that are deposited on its surface.

The results obtained by scientists from the Institute of Chemistry of São Carlos (IQSC) of USP and the Institute of Chemistry (IQ) of Unesp, in Araraquara, generated an article published in the international scientific journal Materials Advances , of the Royal Society of Chemistry.

According to scientists, the new coating may help to maintain the cleanliness of homes and hospitals, even generating savings with the cleaning of spaces.

The researchers are open to partnerships with the industry so that the new material can be placed on the market.

The coating is formed by nanoparticles of silica (SiO₂) and titanium dioxide (TiO2), two compounds that are found in nature in the form of minerals. To test the efficiency of the solution, the researchers prepared an experiment with two groups of ceramic pieces: one with floors that imitate the conventional ones sold on the market and another with floors treated with the new coating.

Scientists simulated a degradation process by applying a purple dye to the pieces. After 30 minutes of UV illumination, the results showed that while commercial floors degraded only 30% of the colorant, materials with the new coating cleared 90% of the paint.

“Self-cleaning floors currently sold on the market are only coated with titanium dioxide and have limited cleaning functions. This is because, during the manufacture of the parts, they are subjected to industrial burning processes that can reach 1,200ºC, affecting the material”, explains Ubirajara Rodrigues Filho, a professor at IQSC and one of the authors of the work. “When ceramic floors are exposed to high temperatures, titanium dioxide is transformed and its self-cleaning properties are reduced”, says the professor.

Because of this limitation, the researchers needed to look for alternatives to ensure that the pieces could withstand overheating, which is essential for ceramics to resist scratches, absorb less water and support weight better, in addition to favoring the proper fixation of their components. After a series of studies, they found the solution in silica, as they discovered that the low-cost material, when used in conjunction with titanium dioxide, provided more thermal stability to the coating. In tests carried out with parts that were subjected to temperatures of 1,200°C, the researchers observed that the silica not only protected the titanium dioxide, preventing it from losing its properties, but also increased the coating’s self-cleaning activity.

The self-cleaning function basically occurs through the action of titanium dioxide, a material capable of absorbing energy from light sources to perform a certain task; in the case of floor coverings, that of degrading organic pollutants. When the floor is exposed to ultraviolet radiation (which can come from the sun, for example), it transforms this radiation into chemical energy to degrade the dirt. In practice, this helps to sanitize the places, ensuring more safety, in addition to avoiding the aesthetic wear of the floors. “In outdoor environments, for example, the coating can be useful to preserve the structures and walls of buildings, as it prevents the accumulation of contaminants”, explains Elias Paiva Ferreira Neto, a researcher at IQ and one of the authors of the research.

“You can activate ultraviolet light in a hospital room so that the titanium dioxide present in the floors cleans the organic matter on its surface, even allowing the economy of cleaning products. Another application would be at home, on an external floor of a barbecue, a scenario in which the light would fall on the ceramic, causing it to degrade grease and dust”, comments the materials engineer who graduated from the São Carlos School of Engineering (EESC) at USP , Victor Martinez, who participated in the work during his scientific initiation (CI) held in Professor Ubirajara’s laboratory.

In the next steps of the study, the researchers intend to verify whether the floor with the new coating also has activity against fungi, viruses and bacteria. In theory, the mechanism responsible for degrading the dirt can also act to disinfect the parts, eliminating pathological agents. If this new function is proven, the new ceramics could, in addition to cleaning organic compounds, help in the sterilization of environments.

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