Murat Akarsu

TiO2 nanoparticle coatings for self-cleaning and antimicrobial application

The photocatalytic effect of TiO2 (especially anatase) is very well known. For the utilization of this effect for hygienic surfaces, especially on plastic surfaces, a wet coating technology has been developed. To enhance the photocatalytic effect of TiO2, anatase nanoparticles with a narrow volume particle size distribution (d1=7nm, d50=9nm, d90=11nm) have been synthesized and surface modified by hydrophobic components in order to disperse them in organic solvents. Since the photocatalytic effect is a non-specific one, and all organic materials are oxidized, a buffer layer stable against oxidation has been used between plastic substrates and TiO2 top layer. The selfcleaning behaviour was determined by the degradation of bovine serum albumin. After 8 h under irradiation (1200 W/m2) in a sun tester the concentration was decreased from 0.3 mg/cm2 under the limit of detection. To show the antimicrobial effect colony forming bacteria (E. coli) were determined after 10 min irradiation (1200 W/m2) leading to an inactivation of about 50% of 1000 CFU/cm2. Additionally the coated plastic surface shows an antifogging behaviour.

Photocatalytic gradient coatings on plastics by spray techniques

Transport coating systems applicable on plastics surfaces by a spray technique are presented. The coatings are based on highly photocatalytically active nanoscaled titania powders, surface modified with silanes containing organic or fluoro-organic side chains. The modification allows for the introduction of the particles in organic inorganic hybrid NANOMER coating systems. In the wet film - due to the evaporation of the solvents - a decompatibilisation of the coated particles to the matrix results in a self organising gradient layer formation with an up-concentration of the active particles at the interface layer between coating and air. After activation by irradiation with artificial or natural UV-light, highly active transparent photocatalysis coatings for a great variety of materials are obtained.