RESUMO
The effect of Riboflavin-5'-phosphate (RFPO4) sensitization on photocatalytic properties of TiO2 film was studied. RFPO4 was adsorbed on film surface to investigate the photophysical properties of TiO2 upon blue-light photoexcitation. The film was characterized through scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis, and diffuse reflectance spectroscopy. The efficiency of the TiO2/RFPO4 film was tested for pollutant elimination in aqueous media in a visible-light-driven system. The phenol paradigmatic model was employed in an aqueous solution as a contaminant target. TiO2/RFPO4 sensitized photodegradation of phenol, which produces catechol, hydroquinone, and benzophenone, was monitored by absorption spectroscopy and HPLC. The results indicated that phenol degradation with TiO2/RFPO4 film was due to the photogeneration of two reactive oxygen species, singlet molecular oxygen (O2(1Δg)) and superoxide radical anion (O2·-) identified through specific detection techniques. The presence of O2(1Δg) is reported here for the first time as generated from a sensitized TiO2 film upon visible-light photoirradiation. Based on the photophysical determinations, a photocatalytic mechanism for TiO2/RFPO4 was established.
RESUMO
A clear case of relationship between the monomer molecular structure and the capability of tuning the morphology of electrodeposited gas bubbles template polymer thin films is shown. To this end, a series of fluorene-bridged dicarbazole derivatives containing either linear or terminally branched polyfluorinated side chains connected to the fluorene subunit were synthesized and their electrochemical properties were investigated. The new compounds underwent electrochemical polymerization over indium tin oxide electrodes to give hydrophobic films with nanostructural and morphological properties strongly dependent on the nature of the side chains. Gas bubbles templated electropolymerization was next achieved by the addition of tiny amounts of water to the monomer solutions, without using surfactants. Within the investigated set of molecules, the nanostructural properties of the soft-templated films obtained from monomers bearing linear side chains could be fine-tuned by adjusting electrochemical parameters, leading to superhydrophobic surfaces.
Assuntos
Nanoestruturas , Interações Hidrofóbicas e Hidrofílicas , Nanoestruturas/química , Água , FluorenosRESUMO
The proherbicide Isoxaflutole (IXF) hydrolyzes spontaneously to diketonitrile (DKN) a phytotoxic compound with herbicidal activity. In this work, the sensitized degradation of IXF using Riboflavin (Rf), a typical environmentally friendly sensitizer, Fenton and photo-Fenton processes has been studied. The results indicate that only the photo-Fenton process produces a significant degradation of the IXF. Photolysis experiments of IXF sensitized by Riboflavin is not a meaningful process, IXF quenches the Rf excited triplet (3 Rf*) state with a quenching rate constant of 1.5 · 107 m-1 s-1 and no reaction is observed with the species O2 (1 Δg ) or O 2 · - generated from 3 Rf*. The Fenton reaction produces no changes in the IXF concentration. While the photo-Fenton process of the IXF, under typical conditions, it produces a degradation of 99% and a mineralization to CO2 and H2 O of 88%. A rate constant value of 1.0 × 109 m-1 s-1 was determined for the reaction between IXF and HOË. The photo-Fenton process degradation products were identified by UHPLC-MS/MS analysis.