"Long before it's in the papers"
December 29, 2011

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Cotton fabrics may clean themselves under sunlight

Dec. 28, 2011
Courtesy of the American Chemical Society
and World Science staff

Au­to­mat­ic dri­ers long ago dis­placed clothes­lines in much of the in­dus­t­ri­al­ized world, though some say the machines should be con­signed to his­to­ry as their pow­er us­age con­tri­butes to glob­al warm­ing.

Now, it seems there is a sec­ond rea­son clothes­lines might make a come­back. Two re­search­ers in Chi­na say it's pos­si­ble to de­sign jeans, sweats or socks that clean and de­o­dor­ize them­selves when hung on a clothes­line in the sun or draped on a bal­co­ny rail­ing. 

They're re­port­ing de­vel­op­ment of a new cot­ton fab­ric that does clean it­self of bac­te­ria and ex­pe­ri­men­tal stains when ex­posed to or­di­nary sun­light. The re­search­ers de­scribe their “visible-light-induced self-clean­ing ma­te­ri­als” in Ap­plied Ma­te­ri­als & In­ter­faces, a jour­nal of the Amer­i­can Chem­i­cal So­ci­e­ty. 

Mingce Long of Shang­hai Jiao Tong Uni­vers­ity and Dey­ong Wu of Hubei Uni­vers­ity for Na­tional­i­ties say their fab­ric uses a coat­ing made from a com­pound of ti­ta­ni­um di­ox­ide, the white ma­te­ri­al used in eve­ry­thing from white paint to foods to sun­screen lo­tions. 

Ti­ta­ni­um di­ox­ide breaks down dirt and kills mi­crobes when ex­posed to some types of light. It al­ready has found uses in self-clean­ing win­dows, kitch­en and bath­room tiles, odor-free socks and oth­er prod­ucts. Self-clean­ing cot­ton fab­rics have been made in the past, the au­thors say, but they self-clean thor­oughly only when ex­posed to ul­tra­vi­o­let rays. So they set out to de­vel­op a new cot­ton fab­ric that cleans it­self when ex­posed to­or­di­nary sun­light.

Their re­port de­scribes fab­ric coat­ed with nano­scopic, or sub-microscopic, par­t­i­cles, made from a com­pound of ti­ta­ni­um di­ox­ide and ni­tro­gen. They re­port that fab­ric coat­ed with the ma­te­ri­al re­moves an or­ange dye stain when ex­posed to sun­light. Additional part­i­cles of sil­ver and io­dine help along the pro­cess, the re­search­ers add, and the coat­ing re­mains in­tact af­ter wash­ing and dry­ing.

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Automatic driers long ago displaced clotheslines in much of the industrialized world, though some say the machines should be consigned to history as their power usage contributes to global warming. Now, it seems there is a second reason clotheslines might make a comeback. Two researchers in China say it's possible to design jeans, sweats or socks that clean and deodorize themselves when hung on a clothesline in the sun or draped on a balcony railing. They're reporting development of a new cotton fabric that does clean itself of bacteria and experimental stains when exposed to ordinary sunlight.The researchers describe their “visible-light-induced self-cleaning materials“ in Applied Materials & Interfaces, a journal of the American Chemical Society. Mingce Long of Shanghai Jiao Tong University and Deyong Wu of Hubei University for Nationalities say their fabric uses a coating made from a compound of titanium dioxide, the white material used in everything from white paint to foods to sunscreen lotions. Titanium dioxide breaks down dirt and kills microbes when exposed to some types of light. It already has found uses in self-cleaning windows, kitchen and bathroom tiles, odor-free socks and other products. Self-cleaning cotton fabrics have been made in the past, the authors say, but they self-clean thoroughly only when exposed to ultraviolet rays. So they set out to develop a new cotton fabric that cleans itself when exposed to ordinary sunlight. Their report describes fabric coated with nanoparticles, or sub-microscopic particles, made from a compound of titanium dioxide and nitrogen. They report that fabric coated with the material removes an orange dye stain when exposed to sunlight. The process is helped along by nanoparticles of silver and iodine, the researchers add, and the coating remains intact after washing and drying.