S. Obregón

Exalted photocatalytic activity of tetragonal BiVO4 by Er3+ doping through a luminescence cooperative mechanism

Er-doped BiVO4 are synthesized by means of a surfactant free microwave assisted hydrothermal method having good photoactivities under sun-like excitation for the degradation of methylene blue. From the structural and morphological characterization, it has been stated that the presence of Er(3+) induces a slight stabilization of the tetragonal phase, probably due to its incorporation in the BiVO4 lattice. The best photocatalytic performances were attained for the samples with Er(3+) content higher than 3 at%. The occurrence of the Er(3+) doped tetragonal BiVO4 clearly induces higher photocatalytic activities. The existence of a luminescence process has been related with the enhanced photoactivity observed.

Improved O2 evolution from a water splitting reaction over Er3+ and Y3+ co-doped tetragonal BiVO4

Erbium–yttrium co-doped BiVO4 with a tetragonal structure is synthesized by means of a surfactant free hydrothermal method. The studied photocatalyst shows good photoactivity under sun-like excitation for the degradation of methylene blue (MB) and for O2 evolution. From structural and morphological characterization, it has been stated that the presence of lanthanides induces the stabilization of the tetragonal phase. This is probably due to the substitutional occupation that occurs in the BiVO4 lattice. The photocatalytic performance under visible-NIR radiation clearly evidences the occurrence of an up-conversion process involved in the overall photo-electronic mechanism. The tetragonal phase Er0.0075,Y0.03–Bi0.9625VO4 system gives the highest O2 evolution rate (425 μmol g−1 h−1) under sun-like excitation, being 8 times higher than that attained for m-BiVO4 (53 μmol g−1 h−1).

Effective photoreduction of a nitroaromatic environmental endocrine disruptor by AgNPs functionalized on nanocrystalline TiO2

Unprecedented photoactivity of silver nanoparticles photodeposited on nanocrystalline TiO2 for the efficient reduction of 4-nitrophenol at room temperature is reported. The use of Na2SO3 as a harmless scavenger agent for the reduction of a nitroaromatic endocrine disruptor yields a valuable 4-aminophenol reagent.

The role of silver nanoparticles functionalized on TiO2 for photocatalytic disinfection of harmful algae

Silver loaded TiO2 samples were prepared by photodeposition of different amounts of Ag+ ions over commercial titanium dioxide (Evonik TiO2 P25) in aqueous media without the presence of sacrificial agents. The obtained photocatalysts were characterized by several techniques such as X-ray powder diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) in order to correlate the effect of the silver amount on the photocatalytic properties of the final nanocomposite. The effect of the silver nanoparticles on the photocatalytic behaviour of TiO2 was evaluated by means of the photodegradation of methyl orange dye and the inactivation of noxious algae Tetraselmis suecica and Amphidium carterae under continuous exposure of low power irradiation UV-light. The sample with 1.5% wt of silver nanoparticles showed the highest photocatalytic elimination of the azo dye and both algae types. According to the results, the cells were deformed during the photocatalytic process by the attack of highly reactive species such as hydroxyl radicals, H2O2 and superoxide ions generated on the TiO2 surface. The algae cells were not regenerated by themselves after the photocatalytic process due the high degree of fragmentation that they suffered during the light irradiation.

Regular ArticleDirect evidence of the photocatalytic generation of reactive oxygen species (ROS) in a Bi2W2O9 layered-structure

In the present work, the Bi2W2O9 photocatalyst has been prepared by an easy and prompt co-precipitation route. From the structural characterization, we have stated that the formation of the Bi2W2O9 is accompanied by a small amount of the Bi2WO6 oxide, which gradually decreases by increasing the calcination temperature. The conduction and valence band edges of the Bi2W2O9 semiconductor were experimentally estimated for the first time using the X-ray photoelectron (XPS) and diffuse reflectance (DRS) spectroscopies. The best photocatalytic performance was attained for the sample calcined at 700°C, which showed the highest production of hydroxyl radicals, superoxide ions as well as the highest photodegradation of the ciprofloxacin drug. In addition, by means of photoluminescence spectroscopy we propose that the effective separation of the photogenerated charge carriers in the sample calcined at 700°C produces a higher production of reactive oxygen species and thus a higher photoactivity under solar-like irradiation conditions.

Direct evidence of the photocatalytic generation of reactive oxygen species (ROS) in a Bi2W2O9 layered-structure

In the present work, the Bi2W2O9 photocatalyst has been prepared by an easy and prompt co-precipitation route. From the structural characterization, we have stated that the formation of the Bi2W2O9 is accompanied by a small amount of the Bi2WO6 oxide, which gradually decreases by increasing the calcination temperature. The conduction and valence band edges of the Bi2W2O9 semiconductor were experimentally estimated for the first time using the X-ray photoelectron (XPS) and diffuse reflectance (DRS) spectroscopies. The best photocatalytic performance was attained for the sample calcined at 700°C, which showed the highest production of hydroxyl radicals, superoxide ions as well as the highest photodegradation of the ciprofloxacin drug. In addition, by means of photoluminescence spectroscopy we propose that the effective separation of the photogenerated charge carriers in the sample calcined at 700°C produces a higher production of reactive oxygen species and thus a higher photoactivity under solar-like irradiation conditions.