One of the proposed substrates within the project was also zinc. During the hydrothermal treatment of zinc the nanoparticles of zinc oxide crystallise at the top of the substrate. To determine the intrinsic photocatalytic properties of ZnO we spent some time on this issue and prepared the ZnO nanoparticles with hydrothermal route from hydrozincite (ZnHC). The photocatalytic activity of ZnO varied with its morphology; ZnHC was not photocatalytic. Rodlike crystals showed a better photocatalytic effect than flower and hedgehog-like crystals. More profound photocatalytic effect was achieved with smaller crystals. The band gap of hydrozincite was 4.1 eV, which was determined and published for the first time. The work was performed in the collaboration with the National Institute of Chemistry, Ljubljana.
COBISS.SI-ID: 5188890
To optimize and simplify the measurements of photocatalysis but still avoid problems as in the case of using dyes (resazurine, methylene-blue, etc.) we systematically test few substances as a model pollutants. In cooperation with colleagues from the University of Porto, Portugal we studied the photocatalytic degradation of caffeine as a model pollutant. The concentration of the caffeine could be easily followed using UV-VIS spectrophotometer. Different photocatalyst were used, various commercial grade nano particles and composites with the addition of the carbon nano tubes.
COBISS.SI-ID: 26271015
Work is dealing with the possibility to use rutile nanoparticles for photocatalytic decomposition of caffeine as a model contaminant. Rutile, a crystal modification of TiO2 has lower bandgap than anatase crystal form. This would mean that for the photocatalytic effect the visible light could be used, and not UV light like in anatase case. Using appropriate synthesis very small rutile nanoparticles, with high specific surface were directly obtained. Particles were characterised with transmission electron microscopy and microanalyis where 12 nm thick amorphous layer was found on the surface. Classically prepared rutile particles with thermally stimulated phase transformation from anatase have very clean and flat surface. We explained that the surface amorphous layer was the main reason why our rutile particles possess quite good photocatalytic properties and classically prepared rutile is practically inactive. The work was partially done at University of Porto, Portugal, where photocatalytic measurements were performed.
COBISS.SI-ID: 26672423
In the paper the synthesis, design and properties of TiO2 based microreactor is described. Firmly adhered TiO2 anatase layer was introduced using original two steps synthesis. In the first step using anode oxidation the few hundreds of nm thick layer of TiO2 nanotube was formed. During second step hydrothermal synthesis was used to form few nm sized anatase nanoparticles at the top of the TiO2 nanotubes. The device was composed of autonomous UV light source (4 UV LED diodes) with corresponding controller, hermetical seal made of UV transparent Plexiglas and active channel, 250 microns wide and 39 cm long coated with anatase TiO2. Using electron microscopy and microanalysis techniques (SEM, FIB, TEM) thorough microstructural investigation was performed where interfaces and individual layers were characterised. Between metal titania and TiO2 few nm sized rutile phase was found. Few hundreds nm thick layer composed of TiO2 nanotubes follow. At the top of the tubes, hydrothermally grown few nm sized anatase nanoparticles were present. In the paper the properties and aging of the reactor was reported. After year and a half of the intensive use, the reactor still exhibit 60% of starting photocatalytic efficiency.
COBISS.SI-ID: 26981415
In the work the degradation of dichloroacetic acid and partial inhibition of the reactor functionality was described. Using complementary analytical methods we explained the origin of this inhibition. Using various analytical techniques (HPLC, EPR, etc.) the reasons for chlorine inhibition were determined. It was found that there is not forming substantial amount of chlorine radicals, but the chlorine ions are preferentially absorbed to the surface of microreactor, inhibiting the absorption of hydroxyl ions and consequently inhibiting the formation of hydroxyl radicals. The work was done in renowned laboratory for photocatalysis and nanomaterials (prof. Detlef Bahnemann) at Faculty for technical chemistry at the University of Hannover. The work was a part of PhD thesis of young scientist Matic Krivec.
COBISS.SI-ID: 27660327