In this study we prepared silica-titania composites with a low SiO2:TiO2 molar ratio. These materials were prepared using a simple sol-gel route in which a hydrothermal treatment was used to obtain mesoporous anatase particles. Pure titania was also synthetized for comparison purposes. These materials were examined by scanning and transmission electron microscopy (SEM and TEM, respectively), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and nitrogen sorption tests. A thin silica coating was formed on the anatase particles. It was observed that the presence of this coating led to samples with an enhanced thermal stability. Indeed, the composites prepared in this work showed an anatase structure and a high specific surface area (SSA), even after their calcination at 800°C. Thus, we believe that the synthetized material present an outstanding SiO2-TiO2 interfacial area associated with a high amount of anatase particles which could improve its photoactive properties.

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On-surface degradation of sildenafil (an adequate substrate as it contains assorted functional groups in its structure) promoted by the Fenton (Fe /H O ) and Fenton-like (M /H O ; M = Fe , Co , Cu , Mn ) systems was investigated by using paper spray ionization mass spectrometry (PS-MS). The performance of each system was compared by measuring the ratio between the relative intensities of the ions of m/z 475 (protonated sildenafil) and m/z 235 (protonated lidocaine, used as a convenient internal standard and added to the paper just before the PS-MS analyzes). The results indicated the following order in the rates of such reactions: Fe /H O ≫ H O ≫ Cu /H O > M /H O (M = Fe , Co , Mn ) ~ M (M = Fe , Fe , Co , Cu , Mn ). The superior capability of Fe /H O in causing the degradation of sildenafil indicates that Fe efficiently decomposes H O to yield hydroxyl radicals, quite reactive species that cause the substrate oxidation. The results also indicate that H O can spontaneously decompose likely to yield hydroxyl radicals, although in a much smaller extension than the Fenton system. This effect, however, is strongly inhibited by the presence of the other cations, ie, Fe , Co , Cu , and Mn . A unique oxidation by-product was detected in the reaction between Fe /H O with sildenafil, and a possible structure for it was proposed based on the MS/MS data. The on-surface reaction of other substrates (trimethoprim and tamoxifen) with the Fenton system was also investigated. In conclusion, PS-MS shows to be a convenient platform to promptly monitor on-surface oxidation reactions.

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An investigation on unusual interface properties of unprecedented ternary composites, formed by the inclusion of assorted proportions of B 2 O 3 into TiO 2 /SiO 2 structure, is conducted herein. The influences of B 2 O 3 content and calcination temperature were evaluated. The precursor TiO 2 /SiO 2 material was synthesized via a simple sol-gel procedure that was followed by B 2 O 3 inclusion via maceration and calcination. The materials were fully characterized and their photocatalytic performance to degrade the Indigo Carmine dye investigated. The material prepared with a B/Ti molar ratio of 1 and at calcination temperature of 350 °C (B 1-350 ) showed the best performance, with a superior photocatalytic activity than that of commercial TiO 2 . The presence of B 2 O 3 -TiO 2 -SiO 2 interfaces in the structure of such material was of critical importance in producing a material with these attractive features. Finally, high resolution mass spectrometry monitoring allowed for the characterization of the main degradation products formed under these conditions.

The present work evaluates the feasibility of using the raw material collected from discarded zinc-carbon batteries as heterogeneous catalyst to degrade the dye Indigo Carmine in an aqueous solution. Besides the evident environmental application, this work also presents an economic alternative for the production of new catalysts used to remediate polluted waters. For this, discarded carbon-zinc batteries were gathered, disassembled and their anodic paste collected. After acidic treatment and calcination at 500˚C, characterization measurements, i.e. flame atomic absorption spectroscopy (FAAS), nitrogen sorption, X-ray diffraction (XRD) and scanning electron microscopy (SEM), revealed that the so-obtained material consisted mainly of ZnMn 2 O 4. This material acts as a heterogeneous catalyst in a Fenton-like process that degrades the dye Indigo Carmine in water. That is probably due to the presence of Mn(III) (manganese in the +3 oxidation state) in this material that triggers the decomposition of hydrogen peroxide (H 2 O 2) to yield hydroxyl radicals (HO •). Moreover, direct infusion electrospray ionization coupled to high resolution mass spectrometry (ESI-HRMS) was employed to characterize the main by-products resulting from such degradation process. These initial results thus indicate that raw materials from waste batteries can therefore be potentially employed as efficient Fenton-like catalysts to degrade organic pollutants in an aqueous solution.