Photocatalytic thin Films Prepared by Plasma Curing of Non‐Reactive Siloxane Dispersions Containing TiO2 Particles

Photocatalytic TiO\u003csub\u003e2\u003c/sub\u003e layers prepared by PVD or CVD processes are already produced industrially. The deposited TiO\u003csub\u003e2\u003c/sub\u003e needs a sufficiently high concentration of the photocatalytically active anatase phase which is produced at higher substrate temperature. As a consequence, the PVD/CVD techniques are limited to heat‐resistant substrates. A novel approach for plasma hybrid coating technology is presented here using the advantages of a cold low‐pressure plasma process in combination with non‐reactive siloxane (polydimethylsiloxane – PDMS) dispersions containing sub‐micron TiO\u003csub\u003e2\u003c/sub\u003e particles for surface functionalisation. As the result, a mechanically stable composite film containing TiO\u003csub\u003e2\u003c/sub\u003e particles with a diameter of up to several times the average coating thickness is generated. The film consists of a top SiO2‐like surface layer and, depending on the initial film thickness, an underlying gradually demethylated and crosslinked siloxane. Although the TiO\u003csub\u003e2\u003c/sub\u003e particles are partially covered by a thin matrix layer of several nanometres, the thin coating shows photocatalytic activity as demonstrated by UV‐degradation of methylene blue. The photocatalytic activity depends on the TiO\u003csub\u003e2\u003c/sub\u003e particle concentration in the film and can be further enhanced by exposing the TiO\u003csub\u003e2\u003c/sub\u003e surface by CF4 plasma etching of the composite film (© 2012 WILEY‐VCH Verlag GmbH \u0026amp; Co. KGaA, Weinheim)