Monatshefte Fur Chemie最新文献

Abstract: Oil blending is often used to enhance the properties of vegetable oils. The admixture of a more thermally stable oil makes the resulting blend more suitable for use in frying. A new method of quality assessment of vegetable oils used in frying is presented in this paper. In this method, ultra-fast gas chromatography coupled with flame ionization detector and chemometrics is employed. Principal component analysis was used for data processing. The results obtained with this method were compared with the results of the Rancimat test and sensory evaluation. It is demonstrated that the addition of olive oil improves the stability of rapeseed oil, and also changes its flavour and aroma profile. In addition, it was found that ultra-fast GC coupled with chemometrics is an effective tool for the assessment of the quality of edible oils. The proposed method does not require sample preparation, and the total time of analysis is less than 2 min.

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Abstract: A relation between oil uptake and cancer as well as induction of hepatic inflammation was shown earlier. It is discussed that the main oil oxidation products-hydroperoxides and carbonyls-might be the reason for the mentioned diseases. In this manuscript quantitative determination of aldehydes which are formed during oxidation of triolein-as a model substance-using the Rancimat 679 is described. The oxidation of 11 g of triolein is carried out at 120 °C sparging air with a flow of 20 dm³/h for 10 h. A series of aliphatic aldehydes starting from hexanal to decanal as well as decenal was identified by LC-MS/MS and quantified as DNPH derivatives. In addition, the total amount of carbonyls was determined. Based on the calibration with hexanal, all other dominant substances were in the similar concentration range with maximum concentrations of 1.6 µmol/cm³ of hexanal, 2.3 µmol/cm³ of heptanal, 2.5 µmol/cm³ of octanal, 3.2 µmol/cm³ of nonanal, 4.0 µmol/cm³ of decanal after 6 h. The total amount of carbonyls reached a maximum after 6 h being 27 µmol/cm³ for triolein without antioxidant. The results of this investigation will be a basis for further toxicological studies on oxidized oils.

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Abstract: A stringent limitation in many optoelectronic devices, such as solar cells and light emitting diodes, is the intrinsic need for a transparent electrode. Uniting relevant aspects, indium tin oxide (ITO) is often the material of choice, however, alternatives are sought and being in particular found in conductive polymers. In this work, we present a novel doping strategy to arrive at highly conducting polymeric material based on poly-3,4-ethylenedioxythiophene (PEDOT). Based on commercial high conductivity PEDOT:PSS (Clevios PH 1000), and a post processing with aqueous triflic acid delivers a material that is both transparent and of low resistivity (5.23 × 10^-4 Ω cm). Furthermore, this material retains its conductive character over a large temperature range, indicating metallic behaviour. This is further supported by positive magnetoconductance effects at low temperatures (1.8-10 K) and extended mean free paths of the conduction electrons are observed-evidencing for a metallic state in this polymer.

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Abstract: In this paper, the square-wave adsorptive stripping voltammetric (SWAdSV) determination of the veterinary drug closantel using a renewable silver amalgam film electrode (Hg(Ag)FE) is presented. As observed in SWAdSV, closantel provided one well-shaped reduction peak suitable for analytical purposes at potential ca. -1.4 V in the Britton-Robinson (B-R) buffer at pH 7.0. At optimal conditions, the SWAdSV response of Hg(Ag)FE for determining closantel was linear over two concentration ranges of 5.0 × 10^-8 to 2.0 × 10^-7 mol dm^-3 and 2.0 × 10^-7 to 1.2 × 10^-6 mol dm^-3 with a detection limit of 1.1 × 10^-8 mol dm^-3. In addition, a relevance of the developed SWAdSV method was successfully verified by the quantitative analysis of closantel in the commercial formulation Closamectin Pour-On with satisfactory results (RSD = 5.8%, recovery = 101.8%). The results showed that the developed procedure can be adequate for screening purposes. Also, the electrochemical behavior of closantel was characterized by cyclic voltammetry, and it was found that closantel exhibited a quasi-reversible behavior with cathodic peak on the forward scan at ca. -1.4 V and anodic peak on the reverse scan at ca. -1.35 V vs. Ag/AgCl in B-R buffer, pH 7.0. As the obtained results showed that the electrode mechanism of closantel is controlled by the adsorption, the effect of adsorption was studied using the electrochemical impedance spectroscopy technique.

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Abstract: Metal halide perovskites have revolutionized the field of solution-processable photovoltaics. Within just a few years, the power conversion efficiencies of perovskite-based solar cells have been improved significantly to over 20%, which makes them now already comparably efficient to silicon-based photovoltaics. This breakthrough in solution-based photovoltaics, however, has the drawback that these high efficiencies can only be obtained with lead-based perovskites and this will arguably be a substantial hurdle for various applications of perovskite-based photovoltaics and their acceptance in society, even though the amounts of lead in the solar cells are low. This fact opened up a new research field on lead-free metal halide perovskites, which is currently remarkably vivid. We took this as incentive to review this emerging research field and discuss possible alternative elements to replace lead in metal halide perovskites and the properties of the corresponding perovskite materials based on recent theoretical and experimental studies. Up to now, tin-based perovskites turned out to be most promising in terms of power conversion efficiency; however, also the toxicity of these tin-based perovskites is argued. In the focus of the research community are other elements as well including germanium, copper, antimony, or bismuth, and the corresponding perovskite compounds are already showing promising properties.

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Abstract: Thioether-functionalised indium aminoalcoholates have been used as single-source precursors in aerosol-assisted CVD processes. The obtained In₂O_3-x S _x oxysulphide deposits show either a single indium sulphide phase for deposits with high sulphide content [>75% (S/(S + O)) for the t-butyl derivatives] or pronounced phase separation in indium oxide and indium sulphide for lower sulphide content [<62% (S/(S + O)) for the n-butyl derivatives]. In addition to thin films, polycrystalline 1D structures are obtained at slightly modified synthesis conditions. The materials are analysed by EDX, XRD, XPS, SEM, and TEM.

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Abstract: Crosslinked colloidal monolayers are promising as templates, lithographic masks, filtration membranes, or membranes for controlled release rates in drug delivery. We demonstrate assembly of monodisperse micron-sized polystyrene (PS) beads at an air/water interface, which are transformed into crystalline monolayers using addition of surface-active agents. Vapor annealing methods with solvents (toluene and xylene) and crosslinking agents (divinylbenzene) were investigated regarding their ability to crosslink these floating monolayers directly at the interface, generating crosslinked membranes with crystal size up to 44 cm², domain size up to 1.9 mm², and nano-sized pores (100-300 nm). The demonstrated fabrication method emphasizes short fabrication time using a simple setup.

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