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Yabing Qi – One of the best experts on this subject based on the ideXlab platform.

  • Air Exposure induced dopant redistribution and energy level shifts in spin coated spiro meotad films
    Chemistry of Materials, 2015
    Co-Authors: Zafer Hawash, Sonia R Raga, Yabing Qi

    Abstract:

    Doping properties of 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-MeOTAD) hole transport layer are investigated by X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and atomic force microscopy under Air Exposure. XPS results reveal that 3 h Exposure of Li-bis(trifluoromethanesulfonyl)-imide (LiTFSI) doped spiro-MeOTAD to Air results in the migration of LiTFSI from the bottom to the top across the spiro-MeOTAD film. AFM images reveal the presence of pinholes with an average diameter of ∼135 nm and a density of ∼3.72 holes/μm2. In addition, cross-sectional scanning electron microscope images reveal that these pinholes form channels across the doped spiro-MeOTAD film. Optical microscopy and Fourier transform infrared microscopy images confirm the presence of large pinholes with diameters in the range of 1–20 μm and a density of ∼289 holes/mm2 as well. The presence of pinholes may play a major role in the migration processes of the LiTFSI within the spiro…

  • Air Exposure induced gas molecule incorporation into spiro meotad films
    Journal of Physical Chemistry Letters, 2014
    Co-Authors: Philip Schulz, James Endres, Gueorgui O Nikiforov, Yuichi Kato, Antoine Kahn, Yabing Qi

    Abstract:

    Combined photoemission and charge-transport property studies of the organic hole transport material 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-MeOTAD) under Air Exposure and controlled environments of O2, H2O + N2, and N2 (1 atm and under dark conditions) reveal the incorporation of gas molecules causing a decrease in charge mobility. Ultraviolet photoelectron spectroscopy shows the Fermi level shifts toward the highest occupied molecular orbital of spiro-MeOTAD when exposed to Air, O2, and H2O resembling p-type doping. However, no traces of oxidized spiro-MeOTAD+ are observed by X-ray photoelectron spectroscopy (XPS) and UV–visible spectroscopy. The charge-transport properties were investigated by fabricating organic field-effect transistors with the 10 nm active layer at the semiconductor–insulator interface exposed to different gases. The hole mobility decreases substantially upon Exposure to Air, O2, and H2O. In the case of N2, XPS reveals the incorporation of N2 molec…

Ann-therese Karlberg – One of the best experts on this subject based on the ideXlab platform.

  • cinnamyl alcohol oxidizes rapidly upon Air Exposure
    Contact Dermatitis, 2013
    Co-Authors: Ida Niklasso, Tamara Delaine, Nurul M Islam, Roge Karlsso, Kristina Luthma, Ann-therese Karlberg

    Abstract:

    Background. Cinnamyl alcohol and cinnamal are frequent fragrance contact allergens. Both are included in the European baseline fragrance mix I, which is used for screening of contact allergy in dermatitis patients.

    Objectives. The aim of this study was to investigate the autoxidation of cinnamyl alcohol and to identify the oxidation products formed on Air Exposure. We also wanted to evaluate the effect of autoxidation on the sensitization potency of cinnamyl alcohol.

    Methods. Samples of commercially available cinnamyl alcohol with and without purification were exposed to Air, and the autoxidation was followed by chemical analysis. The analysis was performed with mass spectrometry (LC/MS/MS). Sensitization potencies of compounds were determined with the murine local lymph node assay (LLNA) in mice.

    Results. Chemical analysis showed that the concentration of cinnamyl alcohol in the Air-exposed samples decreased rapidly over time, and that autoxidation products were formed. Cinnamal, epoxy cinnamyl alcohol and cinnamic acid were identified as oxidation products. According to our study, cinnamal and epoxy cinnamyl alcohol were the first autoxidation products formed. The epoxy cinnamyl alcohol was shown to be the oxidation product with the highest sensitization potency. The analysis of our samples of commercially available cinnamyl alcohol showed that there was already a content of 1.5% cinnamal at the start of the autoxidation experiments.

    Conclusion. Cinnamyl alcohol readily autoxidizes upon Air Exposure, and forms strong sensitizers as determined by the LLNA. Cinnamal was formed in the largest amounts, showing that cinnamal is not only formed via bioactivation, as has previously been shown. A highly sensitizing epoxide was also identified and quantified in the oxidation mixture.

  • lavender oil lacks natural protection against autoxidation forming strong contact allergens on Air Exposure
    Contact Dermatitis, 2008
    Co-Authors: Lina Hagvall, Maria Skold, Johanna Braredchristensson, Anna Borje, Ann-therese Karlberg

    Abstract:

    Background:  Lavender oil is an essential oil frequently used as a fragrance ingredient and in traditional herbal medicine. We have previously studied the effect of Air oxidation on the skin sensitizing potency of the monoterpenes linalyl acetate, linalool and β-caryophyllene, the main constituents of lavender oil.

    Objective:  The aim of this study was to investigate if the autoxidation observed for the single synthetic terpenes, resulting in strong contact allergens, will take place also in lavender oil.

    Methods:  Lavender oil was exposed to Air and the autoxidation was followed by chemical analysis. The sensitizing potency before and after Air Exposure was investigated in mice using the local lymph node assay. Patients with patch test reactions to oxidized linalool were tested to investigate if Air-exposed lavender oil could elicit dermatitis in these individuals.

    Results:  The terpenes oxidized in Air-exposed lavender oil at the same rates as the pure compounds exposed to Air, and the same oxidation products were identified. The sensitizing potency of lavender oil increased accordingly on Air Exposure. Patch testing showed positive reactions to Air-exposed lavender oil and also to oxidized linalyl acetate in patients with contact allergy to oxidized linalool.

    Conclusion:  This study shows that lavender oil lacks natural protection against autoxidation, and that Air-exposed lavender oil can be an important source of Exposure to allergenic hydroperoxides.

  • autoxidation of linalyl acetate the main component of lavender oil creates potent contact allergens
    Contact Dermatitis, 2007
    Co-Authors: Maria Skold, Lina Hagvall, Ann-therese Karlberg

    Abstract:

    Background:  Fragrances are among the most common causes of allergic contact dermatitis. We have in previous studies shown that linalool, present in lavender oil, autoxidizes on Air Exposure, forming allergenic oxidation products. Oxidized linalool was found to be a frequent cause of contact allergy in a patch test study on consecutive dermatitis patients. Linalyl acetate, the main component of lavender oil is commonly used as a fragrance chemical in scented products. Because of structural similarities, linalyl acetate should also be susceptible to oxidation on Air Exposure, forming similar oxidation products as linalool.

    Objective:  The aim of the present study was to investigate the autoxidation of linalyl acetate and the influence of oxidation on its sensitizing potency.

    Methods:  Analyses were performed using gas chromatography, nuclear magnetic resonance spectrometry and mass spectrometry. Sensitizing potencies of compounds were determined using the local lymph node assay (LLNA) in mice.

    Results:  Analyses showed that the content of linalyl acetate decreased over time on Air Exposure and other compounds were formed. Hydroperoxides, an epoxide and an alcohol were identified as oxidation products from linalyl acetate. In the LLNA, linalyl acetate of high purity showed a weak sensitizing potency (EC3 25%). Autoxidation increased the sensitizing potency of linalyl acetate, and a 10 weeks oxidized sample gave an EC3 value of 3.6%. As for linalool, the hydroperoxides were shown to be the oxidation products with the highest sensitizing potency.

    Conclusion:  It is concluded that autoxidation of the weakly allergenic linalyl acetate leads to formation of allergenic oxidation products.

H Beygi – One of the best experts on this subject based on the ideXlab platform.

  • Air Exposure oxidation and photooxidation of solution phase treated pbs quantum dot thin films and solar cells
    Solar Energy Materials and Solar Cells, 2019
    Co-Authors: H Beygi, Seyed Abdolkarim Sajjadi, Abolfazl Babakhani, Jeff F Young, Frank C J M Van Veggel

    Abstract:

    Abstract The Air Exposure oxidation mechanisms of PbS quantum dot (QD) thin films and solar cells are studied in the current paper. As a novel and advantageous method, QD thin films were prepared by the single-step deposition of colloidal QDs treated with different ligands of butylamine (BA), mercaptopropionic acid (MPA), tetrabutylammonium iodide (TBAI), methylammonium iodide (MAI) and methylammonium lead triiodide (MAPbI3, perovskite). Photoluminescence (PL) measurements evaluated the stability of different surface treated PbS QDs during the colloidal to thin film transformation, and over the Air Exposure times. Blue-shift and quenching the PL spectra suggested rapid oxidation of QD thin films at the first times of Air Exposure. However, the oxidation rates significantly reduced for the QD thin films treated with organic MPA and all the inorganic ligands. According to the X-ray photoelectron spectroscopy (XPS) studies, thin films oxidation accompanied with the formation of PbSO3 and PbSO4 compounds on the (100) facets of PbS QDs. Although MAPbI3 treatment led to the complete passivation of QDs in the Air, perovskite shelling partially oxidized to PbO and PbCO3 compounds. Furthermore, the PL enhancement phenomenon observed at the first times of Air Exposure for the TBAI and MAPbI3-treated QD thin films, as a result of their strong surface passivation as well as the photoenhancement and photoelectrification mechanisms. Eventually, p-n and p-i-n structured solar cells were fabricated by the single-step deposition of solution-phase treated PbS QD inks. In this case, inorganic surface treatments not only increased the power conversion efficiency (PCE) of solar cells, but also led to a high stability of fabricated devices in the Air environment (lower than 1% PCE loss after 500 h of storage in the Air).