Katarzyna A. Michalow

Photocatalytic Activity of W-Doped TiO2 Nanopowders

Abstract Polycrystalline tungsten-doped titanium dioxide nanopowders within a dopant concentration of 0-1 at.% were prepared by a one-step flame spray synthesis (FSS). Mixtures of titanium tetra-isopropoxide dissolved in ethanol and tungsten hexacarbonyl solubilized in tetrahydrofuran were used as precursors. The specific surface area (SSA) of the powders was between 40 and 130 m2/g depending on the process parameters, namely the flame combustion stoichiometry and their chemical composition. Irrespective of their composition the powders consisted of spherical particles, as visible by transmission electron microscopy (TEM). They are highly crystallized with anatase as the predominant phase, according to X-ray diffraction (XRD). The band gap energy was determined by spectrophotometric measurement and was between 3.29 eV and 3.34 eV. The photocatalytic performance of the powders was studied by the degradation of methylene blue (MB) and methyl orange (MO) in aqueous suspensions under UV-A (365 nm) as well as visible (400-500 nm) irradiation. The catalytic activity was determined as a function of the tungsten concentration, the specific surface area and the flame combustion stoichiometry. It was found that the TiO2-0.7 at %W particles with high SSA have the highest photoactivity for degradation of MB and MO. This can be explained by the incorporation of the tungsten into the TiO2 crystal lattice as well as modification surface properties.

Synthesis of metabolites of paracetamol and cocaine via photooxidation on TiO2 catalyzed by UV light

Prediction and synthesis of drug metabolites generated by photodegradation using TiO(2)/UV system in aqueous solution was performed to monitor illicit drugs and to support legal actions against drug dealers. Metabolism of paracetamol and cocaine applied as exemplary compounds was monitored by liquid chromatography mass spectrometry (LC-MS/MS) and direct analysis by electrospray ionization mass spectrometry (ESI-MS/MS). The experiments proved that simulated metabolic pathways of the drug samples are efficient and lead to the formation of products that are observed using living organisms or hepatocyte microsomal preparations. Routinely, TiO(2) nanopowders are used for complete degradation of unwanted waste to protect environment. We applied such system for prediction of potential metabolites of harmful substances, such as cocaine. The results demonstrate that TiO(2)/UV oxidative system can be an efficient, complementary method to the in vivo approaches to obtain important metabolites for further studies. Investigations using such methodology may be helpful for toxicologists providing a vital knowledge on metabolites derived from e.g. newly introduced cognitive enhancers (designer drugs), and home-made substances prepared from the over-the-counter tablets (legal highs).