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Now that it’s the middle of a cold snowy winter, I’m looking forward to my annual summer camping trip. What can make camping even more enjoyable? Self-cleaning clothes. And I don’t mean jumping into the river with your clothes on, but simply just leaving them out in the sun. At least, that’s what we may be able to do one day with the self-cleaning cotton developed by Chinese researchers.
Previously cotton fabrics treated with titanium dioxide (TiO2) have shown self-cleaning properties (dye and bacteria removal), but only under ultraviolet irradiation . However, only about 3-5% of the sun’s rays that reach the Earth are in the ultraviolet range . So it’s not very practical to rely on ultraviolet irradiation to clean your clothes. But now researchers have developed a new self-cleaning cotton fabric that just requires visible light, which would be a more efficient use of the sunlight available .
Deyong Wu, from the School of Chemical and Environmental Engineering at Hubei University for Nationalities in China, and his colleague made the new material by treating the cotton fibres with a combination of nitrogen-doped titanium dioxide (N-TiO2) and silver-iodide (AgI).
The team evaluated the self-cleaning properties of the new cotton fibres based on the removal of methyl orange, a dye commonly used in textiles . The dye breaks down with exposure to visible light by a process known as photocatalytic degradation. With just two hours of exposure to visible light, about 70% of the dye was removed from the cotton fibres.
The AgI-N-TiO2 coating on the cotton fibres act as a photocatalyst, a material that promotes chemical reactions in the presence of visible light and is not consumed during the reaction. During photodegradation, oxygen species are generated on the photocatalyst surface and subsequently breakdown the dye. Think, Oxiclean in the laundry.
Ordinarily, the breakdown of a dye would also mean the colour of your clothes is fading, which would be undesirable. However in this case, the ability of the new cotton fabric to breakdown an organic material means the potential for stain removal. Although, the team doesn’t say how well the treated cotton can remove grass or dirt stains.
You won’t find this self-cleaning cotton fabric on store shelves just yet. Researchers will likely need to do additional tests to determine how well this self-cleaning cotton can remove stains from daily wear. But this technology shouldn’t be too far from commercialization, and will likely revolutionize the textile industry.
 Wu, D., Long, M., Zhou, J., Cai, W., Zhu, X., Chen, C., & Wu, Y. (2009). Synthesis and characterization of self-cleaning cotton fabrics modified by TiO2 through a facile approach Surface and Coatings Technology, 203 (24), 3728-3733 DOI: 10.1016/j.surfcoat.2009.06.008
 Wu D, & Long M (2011). Realizing Visible-Light-Induced Self-Cleaning Property of Cotton through Coating N-TiO(2) Film and Loading AgI Particles. ACS applied materials & interfaces, 3 (12), 4770-4 PMID: 22066707
 Chen T, Zheng Y, Lin JM, & Chen G (2008). Study on the photocatalytic degradation of methyl orange in water using Ag/ZnO as catalyst by liquid chromatography electrospray ionization ion-trap mass spectrometry. Journal of the American Society for Mass Spectrometry, 19 (7), 997-1003 PMID: 18430584