A series of titania-transition metal and titania-rare earth element mixtures, with the stoichiometry Ti1-xMxO2, where M=Ce, Eu, La, Nb, W, Y, and x ranging from 0, to 0.05 atoms per formula unit - were prepared via solid-state reaction of the precursor oxides. The products of the synthesis were thermallytreated in air, and two maximum temperatures (900, and 1000 °C) were reached. The addition of transition metal and rare earth ions to the TiO2 structure modified the anatase-to-rutile phase transition temperature, depending on the valence state of the ions added. Transition metals entered the titania structure, but essentially no solid solution between the rare earth elements and TiO2 was detected. The photocatalytic activity of the powders was assessed in liquid-solid and gas-solid phases, under UVA and visible-light irradiation, monitoring the degradation of an organic dye and isopropanol, respectively. The results were explained by taking into account the relative amounts of anatase and rutile in the samples, the specific surface area of the powders, and their optical properties.
COBISS.SI-ID: 1911143
The paper relates only partially to the project (40 %). We report on the synthesis of magnetic iron oxide particles; study of the particles’ formation was undertaken to investigate conditions of precipitation in order to apply it efficiently to cellulose fibre coating procedures. We investigated the formation of iron oxide particles from different starting points. Structural properties (crystallinity, size of the single magnetite crystals), their magnetic and colloidal properties were correlated with the synthesis procedure used. Size and crystallinity of formed particles are also dependent upon the molar concentrations of Fe2+ and Fe3+ ions. Gained insight of the presented synthesis study will prove useful in materials synthesis in the present project.
COBISS.SI-ID: 15846678
Silica, nitrogen, and nitrogen-plus-silica co-doped titania powders were synthesized via sol-gel method. Nitrogen, silica, and co-doping shifted the anatase-to-rutile phase transition toward higher temperatures. Silica was found to enter the anatase lattice, and nitrogen was presumed to enter thetitania crystal structure as well. Nitrogen doping and SiO2/N-co-doping shifted the light absorption toward the visible region.
COBISS.SI-ID: 1879143
To elucidate the importance of the size of capping agents in stimulus-induced release systems from mesoporous silica nanoparticles (MSNs), the effectiveness of poly(propylene imine) dendrimers in controlling the model dye release was studied. MCM-41-type MSNs were synthesized and characterized. Fluorescent compounds (fluorescein disodium salt and carboxyfluorescein) were loaded in the porous structure of the MSNs and entrapped in the silica matrix with the dendrimers of generations I through V by anchoring dendrimers on the MSN surface through disulfide bonds. Stimulus-induced release of the cargo was studied in the presence of dithiothreitol (DTT). Dendrimers of generations I and II were found to be more effective in model drug retention and subsequent release than higher generations. Moreover, MSNs modified with larger amounts of dendrimers lowered the cargo release in the presence of DTT. Besides, pH decrease only was able to trigger release of the cargo. These findings are of importance for optimizing drug delivery systems based on responsive MSNs as they enable tuning of the amount of the released cargo by choosing the capping agent of appropriate size.
COBISS.SI-ID: 5234714
Turn-on fluorescent mesoporous silica nanoparticle-based system was synthesized and characterized. Fluorescein-containing silica nanoparticles were grafted with a dark quencher via disulfide bond. The quencher rendered nanoparticles non-fluorescent by Förster resonance energy transfer (FRET) mechanism. Nanoparticles regained fluorescence upon reduction of disulfides and dissociation of quencher from the particles’ surface. Evident increase of fluorescence of both, suspension and pellet, was present in dithiothreitol-treated sample, while much lower increase was observed in absence of dithiotreitol. Further studies revealed fluorescence intensity is dependent on the concentration of the reducing agent. The present system provides a visual information regarding the onset of the stimulus and, simultaneously, release of the molecules into the medium, thus acting as a release sensor.
COBISS.SI-ID: 5300250