Interplay Effects in the Co-Doping of ZnO Nanowires with Al and Ga Using Chemical Bath Deposition.

The simultaneous co-doping of ZnO nanowires grown by chemical bath deposition is of high interest for a large number of engineering devices, but the process conditions required and the resulting physicochemical processes are still largely unknown. Herein, we show that the simultaneous co-doping of ZnO nanowires with Al and Ga following the addition of Al(NO3)3 and Ga(NO3)3 in the chemical bath operates in a narrow range of conditions in the high-pH region, where the adsorption processes of respective Al(OH)4- and Ga(OH4)- complexes on the positively charged m-plane sidewalls are driven by attractive electrostatic forces. The structural morphology and properties of ZnO nanowires are significantly affected by the co-doping and mainly governed by the effect of Al(III) species. The incorporation processes of Al and Ga dopants are characterized by significant interplay effects, and the amount of incorporated Ga dopants into ZnO nanowires is found to be larger than the amount of incorporated Al dopants owing to energetic considerations. The Al and Ga dopants are located in the bulk of ZnO nanowires, but a part of Al and Ga lies on their surfaces, their incorporation processes in the bulk being enhanced by thermal annealing under oxygen atmosphere. Eventually, the Al and Ga dopants directly affect the incorporation of hydrogen-related defects, notably by annihilating the formation of VZn-nH defect complexes. These findings present an efficient strategy to proceed with the co-doping of ZnO nanowires grown by chemical bath deposition, opening perspectives to control their electronic structure properties with a higher precision.

Substantial brown carbon emissions from wintertime residential wood burning over France.

Brown carbon (BrC) is known to absorb light at subvisible wavelengths but its optical properties and sources are still poorly documented, leading to large uncertainties in climate studies. Here, we show its major wintertime contribution to total aerosol absorption at 370 nm (18-42%) at 9 different French sites. Moreover, an excellent correlation with levoglucosan (r2 = 0.9 and slope = 22.2 at 370 nm), suggesting important contribution of wood burning emissions to ambient BrC aerosols in France. At all sites, BrC peaks were mainly observed during late evening, linking to local intense residential wood burning during this time period. Furthermore, the geographic origin analysis also highlighted the high potential contribution of local and/or small-regional emissions to BrC. Focusing on the Paris region, twice higher BrC mass absorption efficiency value was obtained for less oxidized biomass burning organic aerosols (BBOA) compared to more oxidized BBOA (e.g., about 4.9 ± 0.2 vs. 2.0 ± 0.1 m2 g-1, respectively, at 370 nm). Finally, the BBOA direct radiative effect was found to be 40% higher when these two BBOA fractions are treated as light-absorbing species, compared to the non-absorbing BBOA scenario.

Aniline-based catalysts as promising tools to improve analysis of carbonyl compounds through derivatization techniques: preliminary results using dansylacetamidooxyamine derivatization and LC-fluorescence.

Derivatization techniques based on α-effect amines and H+ catalysis are commonly used for the measurement of carbonyl compounds (CCs), whether in environmental, food, or biological samples. Here, we investigated the potential of aniline-based catalysts to improve derivatization rates of selected carbonyls by using dansylacetamidooxyamine (DNSAOA) as a reagent. Kinetic experiments were performed in aqueous solutions by varying catalyst and CC concentrations and delivered insights into the reaction mechanism. Using anilinium acetate (AnAc), rate constants varied linearly with the catalyst concentration with rate enhancements toward H+-catalyzed reactions as high as ca. 90 and 200 for acetone and benzaldehyde, respectively. Owing to contamination problems when using AnAc, anilinium chloride (AnCl) was chosen for the optimized analysis of real samples at low concentration. Rate enhancements for derivatization reaction of 4.4 (methylglyoxal), 6.0 (glyoxal), 12 (acetone), 20 (formaldehyde), and 47 (hydroxyacetaldehyde) were obtained using 0.1 M AnCl. The optimized method was successfully applied to the determination of the above compounds in natural snow and meltwater samples. Limits of detection (LODs) and limits of quantification (LOQs) were in the 2-14 and 7-41 nM range, respectively, i.e., low enough to allow for the analysis of most natural samples. Satisfactory relative recoveries (92.8 ± 3.8-118.3 ± 4.4%) and intra-day precision (2.7-11.3%) were achieved. Finally, we think that this approach could be applied not only to every α-effect nitrogen reagent-with the most evident profit of lowering derivatization times and particularly those required for low-reactive ketones-but also to the derivatization of CCs onto coated solid sorbents.

Speciation of organic fraction does matter for source apportionment. Part 1: A one-year campaign in Grenoble (France).

PM10 source apportionment was performed by positive matrix factorization (PMF) using specific primary and secondary organic molecular markers on samples collected over a one year period (2013) at an urban station in Grenoble (France). The results provided a 9-factor optimum solution, including sources rarely apportioned in the literature, such as two types of primary biogenic organic aerosols (fungal spores and plant debris), as well as specific biogenic and anthropogenic secondary organic aerosols (SOA). These sources were identified thanks to the use of key organic markers, namely, polyols, odd number higher alkanes, and several SOA markers related to the oxidation of isoprene, α-pinene, toluene and polycyclic aromatic hydrocarbons (PAHs). Primary and secondary biogenic contributions together accounted for at least 68% of the total organic carbon (OC) in the summer, while anthropogenic primary and secondary sources represented at least 71% of OC during wintertime. A very significant contribution of anthropogenic SOA was estimated in the winter during an intense PM pollution event (PM10>50µgm-3 for several days; 18% of PM10 and 42% of OC). Specific meteorological conditions with a stagnation of pollutants over 10days and possibly Fenton-like chemistry and self-amplification cycle of SOA formation could explain such high anthropogenic SOA concentrations during this period. Finally, PMF outputs were also used to investigate the origins of humic-like substances (HuLiS), which represented 16% of OC on an annual average basis. The results indicated that HuLiS were mainly associated with biomass burning (22%), secondary inorganic (22%), mineral dust (15%) and biogenic SOA (14%) factors. This study is probably the first to state that HuLiS are significantly associated with mineral dust.

Use of FTIR spectroscopy coupled with ATR for the determination of atmospheric compounds.

Attenuated total reflection Fourier transformed infrared spectroscopy (ATR-FTIR) can be successfully used for the quantitative determination of small amounts of pollutants like the organic fraction of aerosols. The relation between sample concentration and reflectance is described by the Kubelka-Munk equation and was found to be linearly proportional to the absorption band of some functional group. Several parameters like the matter of solid matrix, the cleaning of the sampling support, the treatment of reflectance spectra and the base line correction considerably influenced the reflectance spectra and facilitated data interpretations. The feasibility of the ATR-FTIR was evaluated by the monitoring of specific organic group bands on filters collected in the French cities of Grenoble and Clermont-Ferrand. We have obtained for hydroxyl group a calibration curve by plotting the relative intensity of reflectance versus the concentration. The linearity was obtained for OH from 1x10(-1) to 1x10(0)molL(-1) with r(2)=0.9959. We can consider that for a direct measurement of the intensity of reflectance, it is possible to perform quantitative ATR-FTIR organic group analysis.