Photocatalytic discoloration of Methyl Orange on innovative parylene–TiO2 flexible thin films under simulated sunlight

Parylene films loaded with TiO2 are reported as hotocatalysts in azo dye discoloration processes. The TiO2 loading of the parylene film was 0.32% (w/w) and the amount of TiO2 on the film was about two orders of magnitude below the TiO2 added in suspension to discolore the same solution of Methyl Orange used as a probe. The parylene/TiO2 films showed a similar activity in the presence of O2 or H2O2 during the discoloration of dyes. This shows the efficient role of O2 as $e_{cb}^-$ scavenger. The photonic efficiency of the parylene/TiO2 film during the Methyl Orange discoloration was 0.04. Based on X-ray photoelectron spectroscopy (XPS) data, the TiO2 particles loaded on the parylene film were shown to be at first encapsulated in the polymer. After the encapsulation is broken, the TiO2 particles are fully exposed to the dye solution. The lack of surface intermediates like C-residues, N and S-species after the photocatalytic process implies an efficient decomposition of the dye at the catalyst interface. During the dye degradation carbonates and carboxylates were detected by XPS and Fourier transform infrared spectroscopy (FTIR) disappearing at the end of the discoloration process. Evidence is presented during the photocatalysis for the formation of a composite parylene/TiO2 film. The formation of this composite involves surface modification of parylene (partial lost of chlorine) in the outermost surface layer with concomitant densification of the TiO2 particles on the parylene film. The parylene film presented a side with high rugosity and one with low rugosity attaching different amounts of TiO2 in each case as observed by transmission electron microscopy (TEM)

A Survey of Bayesian Statistical Approaches for Big Data

The modern era is characterised as an era of information or Big Data. This has motivated a huge literature on new methods for extracting information and insights from these data. A natural question is how these approaches differ from those that were available prior to the advent of Big Data. We present a review of published studies that present Bayesian statistical approaches specifically for Big Data and discuss the reported and perceived benefits of these approaches. We conclude by addressing the question of whether focusing only on improving computational algorithms and infrastructure will be enough to face the challenges of Big Data

Reactivity of oxygen species formed upon N2O dissociation over Fe-ZSM-5 zeolite: CO oxidation as a model

International audienceThe oxidative power toward CO of α-oxygen formed upon N2O dissociation over isolated and binuclear Fe/ZSM-5 zeolite is investigated by means of DFT calculations. The two α-sites [Fe-O]+ and [Fe-(μO)-(μOH)-Fe]+ exchanged in ZSM-5 were considered since their activity in the N2O decomposition was recently shown. Computed electronic properties, charge transfers and frequency analysis of α-oxygen and iron in [O-Fe-O]+ and [OFe-(μO)-(μOH)-FeO]+ suggest a FeII character for the isolated and FeIV for the binuclear Fe-ZSM-5 sites. Addition of CO on oxygen atoms reveals that along the oxidation reaction the valence state for the isolated iron is II and remains relatively constant while a clear change from IV to II is calculated for the binuclear iron. According to DFT calculations CO addition on the α-oxygen from the iron active sites induces a significant length increase of the Fe-α-oxygen bond. Whatever the α-sites, the addition of CO is strongly exothermic and leads to stable minima resembling an adsorbed CO2 on iron active site. This reactivity is in line with the well known high reactivity of α-oxygen and the rapid CO2 formation at low temperatures. Based on the calculated enthalpy values, the adsorption of CO is slightly more favourable on binuclear [OFe-(μO)-(μOH)-FeO]+ than over isolated [O-Fe-O]+ iron site. A comparison of the entropic parameters suggests the opposite with a stronger oxidative power of α-oxygen from isolated over those from binuclear iron site