Andrew blogged about a 'nano TiO2' shampoo some time ago; he didn't know the new application of the photocatalytic properties of TiO2 in coating industry, the self-cleaning coating!
Self-cleaning coatings can be realized by either hydrophobic approach, the well-known Lotus-Effect®, or the hydrophilic approach, the Activ™ coating which mainly consists of TiO2 photocatalyst. An 2005 paper (J. Mater. Chem. 2005, 15, 1689-1694. DOI: 10.1039/b412803f) has summed up the current research of this field. In the latter approach, photocatalysis causes the coating to chemically break down organic dirt adsorbed onto the window, while hydrophilicity causes water to form 'sheets' rather than droplets - contact angles are reduced to very low values in sunlight and the dirt is washed away (by this meaning I suggest the term 'easy-cleaning' rather than 'self-cleaning').
So introduction of TiO2 into shampoo does make sense considering the self-cleaning and water-keeping properties thus gained (shampoo ads says hair to be best in the state of 80-90% dried rather than totally, one of a few things from ads that I do believe). But...how does the TiO2 distinguish the organic dirt from hair (an organic host) and not subject the latter to photocatalysis as well?
2 comments:
Good question. I know there's a bit of an issue in dye-sensitized solar cells with the titania chewing up the dyes.
You've been writing a lot more lately. What's the inspiration?
Papers! Always papers. The only inspiration of this blog is papers.
Post a Comment