Photocatalytic degradation of Prozac® mediated by TiO2 nanoparticles obtained via three synthesis methods: sonochemical, microwave hydrothermal, and polymeric precursor.

Three different synthesis methods were applied to obtain TiO2 nanoparticles: microwave-assisted hydrothermal (TiO2-MW), sonochemical (TiO2-US), and polymeric precursor (TiO2-PP). The nanoparticles thus obtained presented 93% (TiO2-MW) and 92% (TiO2-US) anatase phase, and TiO2-PP 93% rutile phase. The TiO2-US sample performed best during the Prozac® photodegradation assays because of its lipophilic surface, attributable to the C-H groups therein. Additionally, adsorption rate and photodegradation were optimized by adjusting Prozac® solution to pH ~ 8. Following Prozac® photodegradation, quantitative monitoring of its by-products (PPMA, MAEB, and TFMP) was done using HPLC. This quantitative approach led us to conclude that semiconductor photoactivity cannot be discussed solely in terms of the main compound. Lastly, it was seen that these by-products compete with each other in the degradation mechanisms and are influenced by different materials. Graphical abstract.

Annealing effects on the photocatalytic activity of ZnO nanoparticles.

This paper describes the development of ZnO nanoparticles by a chemical method, to test them in the photocatalysis of the degradation of textile dyes, using Rhodamine B (RhB) as a probe reaction. The samples were submitted to different heat treatments in order to observe the annealing effects on the photocatalytical properties, surface decontamination and the consequent particle change, in terms of crystallinity. The as-prepared samples (ZOA) correspond to a metastable phase (oxy or hydroxy zinc acetate) and post annealing leads to ZnO crystallization. In spite of the XRD patterns showing only the ZnO phase for heat treatment at 100 degrees C, FTIR data show that carboxylate groups remains attached to the ZnO surface up to 300 degrees C. Up to 300 degrees C the presence of these carboxylate groups, provided by the synthesis method, showed to be more relevant to photoactivity than the specific surface area. At higher temperatures, crystallinity becomes the dominant factor and an increasing of crystallinity favors the photoactivity.

Deposition of controlled thickness ultrathin SnO2:Sb films by spin-coating.

The technological interest in transparent conductive oxide films (TCOs) has motivated several works in processing techniques, in order to obtain adequate routes to application. In this way, this work describes a new route to obtain antimony-doped tin oxide (ATO) films, based in colloidal dispersions of oxide nanocrystals. The nanoparticles were obtained by a hydrolisis method, using SnCl2 and SbCl3 in ethanolic solutions. The residual halides were removed by dyalisis, obtaining a limpid and transparent colloidal suspension. By this, the method offers the advantage of producing ultrathin films without organic contaminants. This route was employed to produce films with 5, 10, 14, and 18 mol% Sb doping, with thickness ranging from 40 to 70 nm. The physical characterization of the samples showed a uniform layer deposition, resulting in good packing density and high transmittance. A preliminar electrical study confirmed the low electrical resistivity even in the ultrathin films, in such level similar of reported data. The method described is similar in some aspects to layer-by-layer (LbL) techniques, allowing fine control of thickness and interesting properties for ultrathin films, however, with low cost when compared to similar routes.

A simple and novel method to synthesize doped and undoped SnO2 nanocrystals at room temperature.

This work describes the synthesis, at room temperature, of doped and undoped SnO2 nanocrystals (particle size ranging from 1-3 nm) with no thermal or hydrothermal treatment. To the best of our knowledge, this is the first time that the synthesis, at room temperature, of doped and/or undoped SnO2 nanocrystals has been reported. This new synthesis method is based on the controlled oxidation, hydrolysis and polycondensation of tin ions in an ethanol solution. Another novel aspect of this method is the possibility of using surfactants, which may provide improved control over the particle size.