Photocatalytic activity of TiO2-P25@n-TiO2@HAP composite films for air depollution.

We report on an elaboration of new composite photocatalysts (TiO2-P25@ n-TiO2@HAP) based on grafted size-selected 5-nm titanium-oxo-alkoxo nanoparticles on P25-TiO2 nanoparticles and HAP obtained by co-precipitation of salts. The 5-nm oxo-TiO2 particles were prepared in a sol-gel reactor with rapid reagents micromixing. The photocatalytic test of ethylene degradation, in a continuous-flow fixed-bed reactor, showed an increase of the photocatalytic yield for the composite photocatalysts with an addition of HAP. This result was interpreted by a synergy between adsorption and photo-oxidation.

Nucleation and growth kinetics of zirconium-oxo-alkoxy nanoparticles.

Nucleation and growth of zirconium-oxo-alkoxy (ZOA) nanoparticles were studied in a sol-gel process in n-propanol solution at a hydrolysis ratio H between 1.0 and 2.7 and zirconium-n-propoxyde precursor concentrations between 0.10 and 0.15 mol l(-1). The chemical transformations were conducted in quasi-perfect micromixing conditions (Damköhler number Da ≤ 1) and the nanoparticle size evolution was monitored in situ with the light scattering method. The size of primary nanoparticles (nuclei) 2R0 = 3.6 nm was found to be almost independent of the preparation conditions. A remarkable similarity with the titanium-oxo-alkoxy (TOA) nanoparticles was observed. In particular, both systems show the induction stage of the sol-gel growth for a hydrolysis ratio H > 2.0 and stable oxometallate units for H≤ 2.0. However in contrast to TOA, no stable hierarchical ZOA units (clusters) with R0≥R≥ 1.0 nm were observed, which makes this system less stable against aggregation, leading to polydispersed nanoparticles.

Novel nanostructured pHEMA-TiO2 hybrid materials with efficient light-induced charge separation.

We report on a new approach to the fabrication of an electronic material: organic-inorganic pHEMA-oxo-TiO(2) hybrid with efficient light-induced separation of charges. Particular attention is paid to the material nanoscale morphology. The size-selected 5.0 nm titanium oxo-alkoxy nanoparticles are prepared in a sol-gel reactor with rapid (turbulent) fluid micromixing and the ligand exchange results in a stable nanoparticulate precursor in HEMA solution, in which polymerization can be induced thermally or by photons. The obtained hybrid materials demonstrate the highest quantum yield of photoinduced charge separation of 50% and can store photoinduced electrons at a number density above 10% Ti atoms.