Cleaning fabrics with light

Nanotechnology

March 20, 2008

Silk and wool are textile materials that are valued for their strength, warmth, water resistance, and texture. But these natural fibers of the protein keratin lack the stain resistance of synthetic fabrics, and are also generally susceptible to harsh processing conditions.

Now researchers from Monash University and Hong Kong Polytechnic University have developed self-cleaning keratin fibers by modifying them with TiO₂ nanoparticles under benign conditions [Daoud et al., Chem. Mater. (2008) 20, 1242].

The researchers functionalized wool with an abundance of carboxylic groups using succinic anhydride, a mild acylating agent, to improve the affinity of the fibers to anatase TiO₂ nanocrystals. TiO₂ is an efficient photocatalyst and, when the fibers were stained with red wine then exposed to a solar light simulator, the stain degraded almost completely.

“Among the different crystalline forms of TiO₂, the anatase form shows the highest photocatalytic ability,” explains Walid A. Daoud of Monash University. “Biomaterials such as keratins are subject to photodegradation in presence of sunlight. They also have poor resistance to heat and strong chemicals and solvents. The nanocrystals reduce their photodegradation by absorbing the light and converting it into self-cleaning power to decompose contamination.”

The nanocrystalline structure was chosen because of the fact that the smaller the particle, the higher surface area, and thus a higher efficiency of photocatalysis. TiO₂ at the nanoscale is so small that it is invisible and does not alter the texture, color, or feel of the fibers, adds Daoud.

Mark E. Greene