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Recently, the influence of Nb addition in the oxide solid solution of Sn and Ti was investigated with regard to the morphological, structural and electrical properties for the production of chemoresistive gas sensors. (Sn,Ti,Nb)xO2-based sensors showed promising features for ethanol monitoring in commercial or industrial settings characterized by frequent variation in relative humidity. Indeed, the three-metal solid solution highlighted a higher response level vs. ethanol than the most widely used SnO2 and a remarkably low effect of relative humidity on the film resistance. Nevertheless, lack of knowledge still persists on the mechanisms of gas reaction occurring at the surface of these nanostructures. In this work, operando Diffuse Reflectance Infrared Fourier Transform spectroscopy was used on SnO2- and on (Sn,Ti,Nb)xO2-based sensors to combine the investigations on the transduction function, i.e., the read-out of the device activity, with the investigations on the receptor function, i.e., compositional characterization of the active sensing element in real time and under operating conditions. The sensors performance was explained by probing the interaction of H2O and ethanol molecules with the material surface sites. This information is fundamental for fine-tuning of material characteristics for any specific gas sensing applications. [ABSTRACT FROM AUTHOR]

Our recent study in this journal highlighted misassignments of surface intermediates of diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements of published Cu/ZnO (CZ) catalyst systems for methanol synthesis. Here we investigate a recent and very active CZ system, in part promoted by oxidative fluorination (i. e. a Cu/ZnO1–x/ZnF2 system), with realistic operando‐DRIFTS measurements of a 3H2/CO2 gas feed (30 bar, 513 K). This DRIFTS setup is linked to an online GC analysis system and the catalytic performance of the Cu/ZnO1–x catalyst showed a similar performance of the catalysis process in the DRIFTS cell as in the catalyst test station. In the DRIFTS measurements, a very broad absorption band with a maximum at about ∼ 1500 cm−1 (=I1500) is evident. This I1500 band is absent in nitrogen; its intensity increases in pure hydrogen and is particularly high during methanol synthesis. I1500 results from photoionization of an electron residing in a mono‐ionized oxygen vacancy VO+ in the ZnO1–x part of the Cu/ZnO1–x catalyst. Consequently, the I1500 band intensity provides information on the extent of the strong metal‐support interaction SMSI. Therefore, measurement of the I1500 band intensity could be a novel and efficient tool to characterize any CZ‐based catalyst systems online. Mechanistically, the maximum VO+ photoionization I1500 band intensity in a 3H2/CO2 gas stream is coupled to the reaction of CO2 giving the CO2−. radical anion intermediate that is rapidly trapped in the VO2+ site formed. This trapped intermediate may react by hydrogen migration to the well‐known surface formate (1603, 1371, and 1314 cm−1). However, the long‐lived formate with this spectroscopic signature is only a spectator. It is also visible by DRIFTS in catalyst samples that in the same setup do not produce methanol (GC). By contrast, the band intensities of the surface species at 1759, 1691, 1457 and 1398 cm−1 are directly connected to methanol production and the applied WHSV. Therefore, only these surface species are relevant for CO2 hydrogenation to methanol at higher pressure and likely represent true reaction adsorbates/intermediates. [ABSTRACT FROM AUTHOR]

Abstract: By applying the newly developed flow cell (FC) concept, this study investigated the impact of small‐scale spatial variations (millimetre to centimetre) in organic matter (OM) composition (diffusive reflectance infrared Fourier transform spectroscopy), biological activity (zymography), and wettability (contact angle [CA]) on transport processes (tracer experiments, radiography). Experiments were conducted in five undisturbed soil slices (millimetre apart), consisting of a sandy matrix with an embedded loamy band. In the loamy band increased enzyme activities and OM (10 mm apart) were found compared with the sand matrix, with no interrelations although spatial autocorrelation ranges were up to 7 cm. CAs were increased (0–110°) above the loamy band and were negatively correlated with acid phosphatase. Missing correlations were probably attributed to texture variations between soil slices. A general correlation between CA and C content (bulk) were confirmed. Variability in texture and hydraulic properties led to the formation of heterogeneous flow patterns and probably to heterogeneously distributed interfacial properties. The new FC concept allows process evaluation on the millimetre scale to analyse spatial relations, that is, between small‐scale textural changes on transport processes and biological responses. The concept has been proved as a versatile tool to analyse spatial distribution of biological and interfacial soil properties in conjunction with the analysis of complex micro‐hydraulic processes for undisturbed soil samples. The concept may be improved by additional nondestructive imaging methods, which is especially challenging for the detection of small‐scale textural changes. [ABSTRACT FROM AUTHOR]

Abstract: The deposition of organic matter (OM), which is known for its high potential water repellency, on biopore walls can enhance preferential flow through these pores. In this study, OM composition determined with diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy was related to soil water repellency (SWR) determined with sessile drop method, Wilhelmy plate method, and sorptivity tests. We hypothesized that the chemical composition (in terms of potential wettability index; a) is related to the physical properties (i.e., contact angle) of biopore walls, (b) depends on the history of the biopore, and (c) differs from the bulk soil matrix. Thus, the main objective was to identify the relation between OM composition determined with DRIFT spectroscopy and SWR in structured soils. The experiments were carried out on biopores and their surrounding soil matrices, excavated from 2 depths of a haplic Luvisol, with 3 different biopore histories (i.e., root channels, earthworm burrows, and root channels that were short‐term colonized by an earthworm). All measurements at intact biopore surfaces indicated a larger SWR at the surface of biopore walls as compared with the surrounding matrices and showed a higher proportion of hydrophobic functional groups. The OM composition determined with DRIFT spectroscopy correlated (R2 > .7) with contact angles (sessile drop method) that is in line with results of both water sorptivity and Wilhelmy plate method for soils with reduced wettability. The surfaces of short‐term colonized earthworm burrows had the most varying hydrophobic to hydrophilic components (A/B)‐ratio of all investigated biopore surfaces depending on soil depth. For biopore surfaces at this depth, contact angles >90° were frequently observed. The results also indicate that earthworms can lower SWR by aggregate disruption. [ABSTRACT FROM AUTHOR]

Soils on riverine floodplains in Central Europe are commonly enriched in soil organic matter (SOM). We analyzed the quantity and qualitative aspects of SOM in three soil profiles with mollic horizons along the Elbe River (Germany) after physical fractionation by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy to gain deeper insights into the composition of SOM and the formation of these soils. In all horizons, the majority of SOM was recovered in the fraction of particulate OM and in that of sand and aggregates, while SOM in the silt and clay fraction always made up < 20% of soil organic carbon. The C:N ratios of most fractions did not decrease with depth, indicating less decomposed or pyrogenic OM or both. The presence of pyrogenic OM, as a characteristic feature of floodplain soils, was indicated in almost all physical fractions. As derived from DRIFT spectroscopy, SOM was less qualitatively differentiated among the fractions in the soil with the longest duration of flooding, while qualitative differences of SOM were more pronounced in the more aerated ones. The soils have developed from stratified fluviatile sediments and fulfil the criteria of a mollic horizon, irrespective of differences in the composition of SOM. From a soil-genetic point of view, we strongly suggest to classify these soils as Mollic Fluvisols instead of Fluvic Phaeozems, which would accord to the latest WRB classification. [ABSTRACT FROM AUTHOR]

During the last years the need for non-invasive and non-destructive analytical methods brought to the development and application of new instrumentation and analytical methods for the in-situ analysis of cultural heritage objects. In this work we present the application of a portable diffuse reflectance infrared Fourier transform (DRIFT) method for the non-invasive characterization of colorants prepared according to ancient recipes and using egg white and Gum Arabic as binders. Approximately 50 colorants were analyzed with the DRIFT spectroscopy: we were able to identify and discriminate the most used yellow (i.e. yellow ochres, Lead-tin Yellow, Orpiment, etc.), red (i.e. red ochres, Hematite) and blue (i.e. Lapis Lazuli, Azurite, indigo) colorants, creating a complete DRIFT spectral library. The Principal Component Analysis–Discriminant Analysis (PCA–DA) was then employed for the colorants classification according to the chemical/mineralogical composition. The DRIFT analysis was also performed on a gouache painting of the artist Sutherland” and the colorants used by the painter were identified directly in-situ and in a non-invasive manner. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dry grinding and aging of arsenides produced thin heterogeneous oxide and hydroxide layers. • Arsenides conditioning under alkaline conditions enhanced the oxidation effect on surfaces. • CuSO 4 activation improves the adsorption of xanthate on the arsenide surfaces, mainly under alkaline conditions. • PAX adsorption effectiveness depends on arsenides surface physico-chemistry. Skutterudite ((Co,Ni,Fe)As 3), gersdorffite (NiAsS), and nickeline (NiAs) are some common arsenic- and nickel-bearing minerals often encountered worldwide in mine ores and mine wastes. These arsenides can be the source of arsenic- and nickel-contaminated neutral drainage (CND) when subjected to atmospheric conditions. Environmental desulphurization by froth flotation is a promising technique used to prevent this contamination. This study fills a knowledge gap in the evolution of the surface physicochemistry of these arsenides under different conditions, in order to determine the best conditions for flotation and successful environmental desulfurization. This work evaluates the impact of grinding, air-oxidation (aging), and conditioning on the mineral surfaces, as well as their interaction with potassium amyl xanthate (PAX) as a flotation collector. The effect of activation by copper sulphate (CuSO 4) was also examined. The adsorption of PAX was analyzed by ultraviolet–visible (UV–Vis) spectrophotometry and zeta potential measurements, and the surface was characterized using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) allowing the speciation of the oxidation layer across the different mineral surfaces. Dry grinding and aging of the minerals produces thin heterogenous oxide and hydroxide layers that are mainly enriched in arsenic oxides, especially in the form of arsenate (as an oxidation product of arsenite), and arsenic, cobalt, and nickel sulphates and hydroxides. Arsenides conditioning under alkaline conditions enhances the oxidation effect on the mineral surfaces compared to natural conditions. Copper sulfate activation was found to be effective on the arsenides and improves the adsorption of xanthate on the oxidized arsenide surfaces, especially under alkaline conditions. The results of this study provide a better understanding of the surface chemistry of these minerals before and after collector adsorption, which should impact their flotation behavior. [ABSTRACT FROM AUTHOR]

Abstract: There is a limited knowledge on the role of soil texture and clay mineralogy in governing the content and composition of organic matter (OM) associated with physically-separated fractions in major Thai soils. To extend the understanding in this context, we sampled a range of Thai soils representing four major mineralogy groups, i.e. siliceous, mixed mineralogy, kaolinitc, and smectitic soils. The clay fraction and four density fractions [two particulate OM, free-light (fPOM) and occluded (oPOM), <1.85gcm−3; and two heavy fractions, 1.85–2.60gcm−3 (HFOM1.85–2.60) and >2.60gcm−3 (HFOM>2.60)] of soils from the top- and sub-soil horizons with varying clay content (58–967gkg−1) and mineralogy were analyzed for organic carbon (OC) and total nitrogen (N) contents. Additionally, chemical composition of the OM in the clay fraction of soils from 0–20cm, 20–40cm and 40–70cm and the four density fractions from soils at 20–40cm depth was characterized using diffuse reflectance infrared Fourier transformed (DRIFT) spectroscopy. The OM associated with oPOM (OC only) and HFOM1.85–2.60 (OC and total N) fractions was significantly increased with increasing clay content among soil groups and the degree of association depended on the dominating clay mineral (albeit significantly at P <0.05 for some soil groups only). The relative proportion (%rA) of aliphatic-C in the clay and HFOM1.85–2.60 fractions significantly increased with increasing sand content, and significantly decreased with increasing clay content. Whereas, opposite relationships were observed for the aromatic-C and amide N (amide-II) with sand and clay contents, respectively. The organic-mineral fractions (clay or HFOM1.85–2.60) of the coarse-textured siliceous soils were enriched with aliphatic-C and depleted in amide N, whereas the organo-mineral fractions of the fine-textured soils were enriched with aromatic-C and amide N. Aliphatic-C represented the dominating organic structure in the siliceous soils, whereas aromatic-C and amide N represented typical forms of OM in the fine-textured soil groups. The present study provided insights into the role of soil texture and clay mineralogy in governing the content and composition of OM pools in Thai soils with relevance for sustaining soil fertility and mitigating C emissions. [Copyright &y& Elsevier]

The adsorption of NH and NO over fresh and thermally treated Fe-BEA catalysts were studied using in situ DRIFT spectroscopy to follow the evolution of different iron species before and after thermal treatment. Fe-BEA samples were prepared and thermally treated in air at 700 °C for 12, 24 and 48 h, and at 800 and 900 °C for 48 h. Compared to the fresh sample, the NH adsorption experiments indicate dealumination of the zeolite and iron oxide particle growth for the aged samples. Furthermore, the NO adsorption experiments show distinct absorption peaks which are assigned to isolated iron species, iron clusters and larger iron oxide particles. The thermally treated samples show migration of isolated iron species from the zeolite pores forming iron oxide particles. Further ageing results in a continuous migration and formation of larger iron oxide particles located on the external surface of the zeolite. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: The application of FTIR ATR (Fourier transform infrared attenuated total reflection), DRIFT (diffuse reflectance infrared Fourier transform) and FT Raman spectroscopy for the quantification of thiamine hydrochloride, or vitamin B1, in tablets was compared. PLS (partial least squares) calibration models were built and validated using the spectra of 40 samples containing vitamin B1 and excipients. To evaluate the predictive ability of these models, the relative standard errors of prediction (RSEP) were calculated. In the case of vitamin B1 determination from the Raman data, RSEP error values of 1.5 % and 2.1 % were obtained for the calibration and validation data sets, respectively. When DRIFT spectra were applied, the respective RSEP errors were found to be 2.1 % and 2.2 %. For ATR models, these errors amounted to 3.1 % and 3.2 %, respectively. Commercial tablets containing 25mg of thiamine hydrochloride were quantified using the developed models. Derived concentrations correlated strongly with the results of the reference analysis and yielded recoveries of 99.2–100.8 %. Each of the three applied spectroscopic techniques can be employed as fast and reliable alternatives to the standard pharmacopeial methods of vitamin B1 quantification in tablets. DRIFT spectroscopy has the highest potential to become a routine technique for the quantification of solid mixtures within the pharmaceutical industry. [Copyright &y& Elsevier]

Abstract: Three ultrafiltration membranes, polyether-sulfone (PES), polyacrylonitrile (PAN) and cellulose acetate (CA) have been tested in order to study fouling and the removal of natural organic matter (NOM) from three natural source waters having different physical and chemical characteristics. The physically reversible fouling depended on the system of feed water and membrane type. Physically reversible fouling was significant for the system which consisted of hydrophobic feed medium–hydrophobic membrane (Las P, Lasek S — PES) as well as for the system: hydrophilic feed medium–hydrophilic membrane (Zabie D — CA). The change of membrane properties (the contact angles) after the filtration was observed. The foulants remained after physical cleaning render the PES and PAN membranes more hydrophilic, while CA membrane became more hydrophobic. The filtration cakes extracted from the membranes were analyzed by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. According to spectra the water from Zabie D contained relatively more polysaccharide-like than protein-like substances, while the opposite relations between two groups were noted for Lasek S. The water form Lasek S demonstrated highest potential for fouling towards tested membranes. Las P sample showed more humic acid-like characteristics. [Copyright &y& Elsevier]

Abstract: The interaction of di-n-butyl phthalate (DBP as the internal donor) with AlEt3 cocatalyst was studied by DRIFT spectroscopy for the DBP/MgCl2 sample and supported TiCl4/DBP/MgCl2 catalysts. For DBP/MgCl2 sample, it was shown that AlEt3 partially removes all types of DBP complexes from the MgCl2 surface and adsorbs on surface sites released by the removal of DBP. In the case of supported catalysts, the cocatalyst predominantly removes more weak DBP complexes. In addition, the cocatalyst completely removes loosely coordinated DBP and surface complexes of phthaloyl chlorides formed at the catalyst preparation. A part of removed DBP can adsorb again on the catalyst surface as complexes with surface alkylaluminum chloride compounds. The external donor alkylalkoxysilane does not markedly influence the removal of DBP complexes from the catalyst surface. [Copyright &y& Elsevier]

Abstract: The interaction of AlEt3 cocatalyst with the internal donor (ethyl benzoate–EB) in the supported Ziegler–Natta (TiCl4/EB/MgCl2) catalysts and the EB/MgCl2 support was studied by DRIFT spectroscopy. For EB/MgCl2 samples, it was shown that AlEt3 firstly removed the more weak surface complexes of EB from the MgCl2 surface and competed with EB at adsorbtion for releasing sites of the MgCl2 surface. EB, as the external donor, keeps constant the initial content and distribution of surface complexes of EB at the interaction of the AlEt3/EB mixture with the EB/MgCl2 support. At the interaction of AlEt3 with the TiCl4/EB/MgCl2 catalysts one type of surface complexes of EB is mainly removed. A part of removed EB adsorbs again on the catalyst surface in the form of complexes with aluminum-containing compounds. At the interaction of the catalyst with the AlEt3/EB mixture the EB content in the catalyst changes slightly, but the distribution of different surface complexes of EB in the catalyst changes noticeably compared to that in the initial catalyst. EB, as the external donor, adsorbs both on surface MgCl2 sites released at the removal of the internal donor and on aluminum-containing compounds adsorbed on the catalyst surface. [Copyright &y& Elsevier]

Knowledge about the thermal properties of zeolites is extremely important due to their potential application in the chemical industry. In this work, the thermal stability and the dehydration process of zeolite A were investigated by in situ high temperature Fourier transform infrared spectroscopy. The progress of thermal decomposition that zeolite A underwent during the controlled temperature increase in the range of 25–600 °C was determined by the DRIFT spectroscopic method. Infrared spectra are presented and discussed for this compound on the basis of the crystal structure. Based on the courses of the obtained DRIFT spectra, it was found that, during heating, water was gradually removed from the structure of the material, followed by dehydration and formation of hydrogen bonds. It was established that the process of thermal degradation began as early as 550 °C. The analysis of the obtained results of structural tests can be repeated on other materials from the zeolite group and complements the research work on the thermal analysis of these materials. [ABSTRACT FROM AUTHOR]