Ozone is an important oxidant in the environment.To study the nature of multiphase ozonolysis, an unsaturated triglyceride, triolein, of the type present in skin oil, biological membranes, and most cooking oils was oxidized by gas-phase ozone on a surface. A high-performance liquid chromatography/ electrospray ionization mass spectrometry (HPLC-ESI-MS) method was developed for analyzing triolein and its oxidized products. Upon exposure to ozone, the decay of thin coatings of triolein was observed, accompanied by the formation of functionalized condensed-phase products including secondary ozonides (SOZ), acids, and aldehydes. By studying the reaction kinetics as a function of average coating thickness and ozone mixing ratio, we determined that the reactive uptake coefficient (γ) is on the order of 10 −6 to 10 −5 . It is also concluded that the reaction occurs in the bulk without a major interfacial component, and the reacto-diffusive depth of ozone in the triolein coating is estimated to be between 8 and 40 nm. The specific nature of the reaction products is affected by the reactions of the Criegee intermediate formed during ozonolysis. In particular, although an increase in the relative humidity to 50% from dry conditions has no effect on the kinetics of triolein decay, the yield of SOZs is significantly depressed, indicating reactions of the Criegee intermediates to form hydroperoxides. Once formed, the SOZ products are thermally stable over periods of at least 48 h at room temperature but decomposition was observed under simulated outdoor sunlight, likely forming organic acids. From an environmental perspective, this chemistry indicates that SOZs and other oxygenates will form via ozonolysis of oily indoor surfaces and skin oil.

The thermal decomposition products and kinetics of two typical organic−inorganic halide perovskites, CH 3 NH 3 PbI 3 (MAPbI 3 ) and HC(NH 2 ) 2 PbI 3 (FAPbI 3 ), were investigated via simultaneous thermogravimetric analysis coupled with Fourier transform infrared spectroscopy. NH 3 and CH 3 I were verified as the major thermal decomposition gases of MAPbI 3 . Furthermore, for the first time, methane (CH 4 ) was observed as a thermal degradation product of MAPbI 3 at elevated temperatures. In contrast to conventional wisdom, (HCN) 3 (trimerized HCN) and NH 3 were demonstrated as the major gaseous decomposition products of FAPbI 3 at lower temperatures, while HCN and NH 3 became dominant at high temperatures (>360 °C). The hybrid experimental/theoretical results presented in this study will further our understanding of the perovskite decomposition mechanism and provide new insights into designing of long-term stable perovskite-based devices.

Gas-phase H2O2 is a prominent oxidant in the atmosphere. It also induces lung tissue damage and forest decline. Although it is known that ozonolysis of gas-phase alkenes leads to H2O2 formation at high relative humidities (RHs), little is known about this chemistry via gas-surface heterogeneous oxidation. Here, we quantitatively investigated the formation of H2O2 from surface ozonolysis of unsaturated lipids commonly found in human skin oil and atmospheric aerosol. This process is initiated by water reacting with Criegee intermediates (CIs), forming α-hydroxyhydroperoxides (α-HHPs) as the key intermediate products. α-HHPs are thermally stable molecules that act as reservoirs of H2O2 under dry conditions, prior to rapid decomposition to release H2O2 in the presence of water vapor. The upper limit of the α-HHP lifetime derived from oxidized methyl oleate was roughly 2 min at 50% RH. The molar H2O2 yields (relative to ozone consumption) vary from 7% to 35% for triolein, methyl oleate, and squalene, with no significant dependence on relative humidity from 50% to 80%. In contrast, oleic acid has the lowest H2O2 yield (∼2%), likely due to a more competitive reaction between CIs and its carboxylic acid headgroup. The implications of this chemistry in atmospheric and indoor environments are discussed.

Carrier lifetime in flexible CH3NH3PbI3 films increases with increasing tensile strain, and conversely decreases with increasing compressive strain.

Commonly found in atmospheric aerosols, cooking oils, and human sebum, unsaturated lipids rapidly decay upon exposure to ozone, following the Criegee mechanism. Here, the gassurface ozonolysis of three oleic acid-based compounds was studied in a reactor and indoors. Under dry conditions, quantitative product analyses by 1 H NMR indicate up to 79% molar yield of stable secondary ozonides (SOZs) in oxidized triolein and methyl oleate coatings. Elevated relative humidity (RH) significantly suppresses the SOZ yields, enhancing the formation of condensed-phase aldehydes and volatile C9 products. Along with kinetic parameters informed by molecular dynamics simulations, these results were used as constraints in a kinetic multilayer model (KM-GAP) simulating triolein ozonolysis. Covering a wide range of coating thicknesses and ozone levels, the model predicts a much faster decay near the gas−lipid interface compared to the bulk. Although the dependence of RH on SOZ yields is well predicted, the model overestimates the production of H 2 O 2 and aldehydes. With negligible dependence on RH, the product composition for oxidized oleic acid is substantially affected by a competitive reaction between Criegee intermediates (CIs) and carboxylic acids. The resulting α-acyloxyalkyl hydroperoxides (α-AAHPs) have much higher molar yields (29−38%) than SOZs (12−16%). Overall, the ozone−lipid chemistry could affect the indoor environment through "crust" accumulation on surfaces and volatile organic compound (VOC) emission. In the atmosphere, the peroxide formation and changes in particle hygroscopicity may have effects on climate. The related health impacts are also discussed.