Doping TiO2 films with carbon nanotubes to simultaneously optimise antistatic, photocatalytic and superhydrophilic properties

Pure and multiwall carbon nanotube (MWCNT)-
doped titanium dioxide (TiO2) films, synthesised from two
sol–gel routes (alcoholic and aqueous) and deposited by dipcoating
on glass, have been developed as conductive, photocatalytic
and superhydrophilic materials. While already
crystallised in anatase structure at low temperature when
synthesised in water, samples prepared in alcohol are amorphous.
Their crystallisation in air has been studied at
increasing temperatures. Effective incorporation of functionalised
MWCNTs is confirmed in both aqueous and alcoholic
samples with a closer interaction with TiO2 particles in
the case of aqueous synthesis. In alcoholic samples, 400 C
seems to be an optimised calcination temperature since
300 C does not allow crystallisation into anatase and 500 C
removes MWCNTs through burning. The purpose of
MWCNT doping is to obtain coatings that exhibit easy-toclean
or self-cleaning properties. This can be achieved
through an optimised combination of electrical conductivity
(for antistatic property), photoactivity and superhydrophilicity.
These three properties require the crystallisation of TiO2
into anatase. MWCNT doping dramatically increases both
conductivity and photocatalytic activity, especially in alcoholic
samples for the former and in aqueous samples for the
latter. On the other hand, MWCNT introduction does not
significantly affect the (super)hydrophilicity of films, which
depends solely on the crystallinity of TiO2.