Typical SEM images of (a) N-TiO2-cotton and (b) AgI-N-TiO2-cotton. Reprinted with permission from ACS Appl. Mater. Interfaces, DOI: 10.1021/am201251d. Copyright 2011 American Chemical Society.
A recent press release from the American Chemical Society about a coating that imparts self-cleaning properties to cotton caught my eye, probably because I am my family’s laundress, or perhaps because I’ve spent a good amount of December collecting new garments for Christmas gifts and making sure they are washable.
In any case, the story caught the attention of Gizmag‘s Ben Coxworth, too, and he wrote a succinct summary of the research work. Here it is—
Treated cotton cleans itself when exposed to sunlight
For some time now, we’ve been hearing about the benefits of drying our laundry outside on the clothesline. We save money and energy by not running the dryer, the sunlight kills germs, and we don’t run the risk of generating harmful dryer emissions. In the future, however, we might also end up washing our clothes by hanging them outside – scientists in China have successfully used sunlight to remove orange dye stains from cotton fabric, that was treated with a special coating.
Mingce Long and Deyong Wu created the coating, which combines titanium dioxide and nitrogen. When exposed to sunlight, dirt on fabric treated with the coating breaks down, and microbes die. While the coating in its basic form is effective, it was found that it does an even better job at dispersing dye coloration when silver and iodine nanoparticles are added. Additionally, it is able to remain intact and active after washing and drying.
Although light-activated self-cleaning fabrics have been created previously, all of those required concentrated ultraviolet light, as opposed to natural sunlight.
Should the coating eventually be commercialized, however, there are doubtless many people who would want nothing to do with it. Although titanium dioxide is now an active ingredient in products such as sunscreen, cosmetics and paint, studies have shown that it can cause genetic damage in mice and brain damage in fish. This has led to concerns over the effect that it could have on humans, and the environment.
A paper on the coating was recently published in the journal ACS Applied Materials & Interfaces.
On the last point about the safety of titania nanoparticles, our recent post about ZnO nanoparticles for suncreen seems to indicate that human skin is an effective barrier to nanoparticles. Full toxicological testing is warranted, of course.
The paper’s authors do not speculate about potential applications, but my guess is that interest would be strong in the medical community, for example, in parts of the world where medical supplies are scarce or unreliable, the ability to make and sanitize dressings onsite could be important.