Photocatalytically Active Polyelectrolyte/Nanoparticle Films for the Elimination of a Model Odorous Gas

Abstract

Virtually transparent films of Aeroxide TiO(2) P25 were fabricated via layer-by-layer assembly with sodium poly(styrene sulfonate). Nanoscale films are formed on model surfaces for characterization or inside of cylindrical reactors for investigating the catalytic properties. Films are fairly homogeneous and smooth over large areas and show different optical interference colors depending on film thickness. The application-relevant photocatalytic performance of such films toward on-flow degradation of hydrogen sulfide under UV-A irradiation was investigated. Scanning electron microscopy reveals a nanoporous structure allowing for the permeation of gas. Consequently, the catalytic efficiency of the films increases with increasing film thickness retaining a considerable activity of the corresponding nanoparticle powder. Scheme 1 depicts in a general way the functionalized reactor and the principle of the measurement.

Tailoring preparation, structure and photocatalytic activity of layer-by-layer films for degradation of different target molecules

“…During film rearrangement, film thickness does not further increase and new material is deposited on the interior of the film, reducing porosity. The amount of TiO 2 deposited was estimated to be 1.1, 4.1 and 5.1 g/cm 2 for (0.67/1) 5 , (6/9) 5 and (20/30) 5 films, respectively [2]. Deposition speed can be dramatically enhanced by agitation, using a magnetic stirrer (Fig.…”

“…1). At this wavelength, PSS does not absorb radiation so only the amount of TiO 2 is measured [2]. Film thickness was measured for some samples using ellipsometry.…”

“…LbL deposition was performed by manual dip-coating using an established procedure [2]. Dipping solutions were prepared using MilliQ water and kept in polypropylene bottles.…”

“…Kotov et al [7] were the first to introduce positively charged titanium dioxide (TiO 2 ) nanoparticles in a LbL assembly using poly(diallylmethylammonium chloride) counter-anions. Shortly after, Liu et al [8] prepared transparent TiO 2 films using poly(styrene sulfonate) (PSS) as the anion, a method that was adopted by several other groups [2,3,9]. For TiO 2 /polymer composites, Kim and Shiratori [9] showed that the use of weak polyelectrolytes results in thick films with high surface roughness whereas strong polyelectrolytes such as PSS give rise to dense films.…”

“…Such a nanoparticle film ideally maintains high porosity and surface area, is robust and depending on the application, may be optically transparent (e.g. photocatalytic glass) [2,3].…”