The Effect of Calcination Temperature on Structure and Photocatalytic Properties of WO 3 /TiO 2 Nanocomposites

Series of WO 3 /TiO 2 nanocomposites were obtained by hydrothermal method followed by calcination in the temperature range from 400 ∘ C to 900 ∘ C. The characteristics of photocatalysts by X-ray diffractometry (XRD), scanning electron microscope (SEM), and diffuse reflectance spectroscopy (DRS) showed that increasing the calcination temperature from 400 to 900 ∘ C resulted in change of photocatalytic activity under UV-Vis light. Moreover, the amount of WO 3 crystalline phase and amorphous phase in WO 3 /TiO 2 aggregates, as revealed by XRD analysis, was dependent on the calcination temperature. The WO 3 /TiO 2 samples with 8 mol% load of WO 3 in respect to TiO 2 calcinated at 500 and 800 ∘ C possess the highest photocatalytic activity in reaction of phenol degradation, which is about 1.2 and 1.5 times that with calcination at 400 ∘ C. The increase in calcination temperature above 400 ∘ C resulted in increase of WO 3 crystallinity and reduction of the amount of amorphous phase in the nanocomposite structure. Moreover, the annealing of nanocomposites above 700 ∘ C decreases the value of optical band gap energies of obtained WO 3 /TiO 2 nanomaterials

On the mechanism of photocatalytic reactions on CuxO@TiO2 core-shell photocatalysts

Titania (titanium(IV) oxide) is a highly active, stable, cheap and abundant photocatalyst, and is thus commonly applied in various environmental applications. However, two main shortcomings of titania, i.e., charge carrier recombination and inactivity under visible-light (vis) irradiation, should be overcome for widespread commercialization. Accordingly, titania has been doped, surface modified and coupled with various ions/compounds, including narrower bandgap semiconductors, such as oxides of copper and silver. Unfortunately, these oxides are not as stable as titania, and thus loss of activity under long-term irradiation (photo-corrosion) has been observed. Therefore, this study has focused on the preparation of stable coupled photocatalysts, i.e., CuxO@TiO2 core-shell nanostructures, by the microemulsion method from commercial Cu2O as a core and TiO2 (ST01-fine anatase) as a shell. The photocatalysts have been characterized by DRS, SEM, TEM, XRD, XPS and reversed double-beam photoacoustic spectroscopy (RDB-PAS) methods, and activity tests under UV (anaerobic dehydrogenation of methanol and oxidative decomposition of acetic acid) and vis (phenol oxidation) irradiation. The higher activities of coupled photocatalysts than their counterparts have been found in all studied systems under UV/vis irradiation. Moreover, long-term experiments (10 h) have shown high stability of CuxO@TiO2. However, the change of oxidation state of copper has also been observed, i.e., to negative and positive values, confirming the charge transfer according to the Z-scheme under UV irradiation and type-II heterojunction under vis irradiation, respectively. The property-governed activity and the mechanism have been discussed in detail

Primary Investigation of the Preparation of Nanoparticles by Precipitation

The absorption, distribution, biotransformation and excretion of a drug involve its transport across cell membranes. This process is essential and influenced by the characteristics of the drug, especially its molecular size and shape, solubility at the site of its absorption, relative lipid solubility, etc. One of the progressive ways for increasing bioavaibility is a nanoparticle preparation technique. Cholesterol, cholestenolone and pregnenolone acetate as model active pharmaceutical ingredients and some of the commonly used excipients as nanoparticle stabilizers were used in the investigated precipitation method that was modified and simplified and can be used as an effective and an affordable technique for the preparation of nanoparticles. All 120 prepared samples were analyzed by means of dynamic light scattering (Nanophox). The range of the particle size of the determined 100 nanoparticle samples was from 1 nm to 773 nm, whereas 82 samples contained nanoparticles of less than 200 nm. Relationships between solvents and used excipients and their amount are discussed