Spectrum and stability of oxygen iodide charge-transfer complex

Levanon, Haim

doi:10.1021/j100726a038

Cited by 14 publications

(9 citation statements)

References 6 publications

(8 reference statements)

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“…Halogen species were detected using a chemical ionization mass spectrometer (CIMS), described previously by Liao et al (2011) and Pratt et al (2013). Chemical ionization is achieved by ion-molecule reactions that occur between iodide-water reagent clusters, I(H 2 O) − n in N 2 , and the gasphase analytes in zero air.…”

Section: Cimsmentioning

confidence: 99%

pH-dependent production of molecular chlorine, bromine, and iodine from frozen saline surfaces

Halfacre¹,

Shepson²,

Pratt³

2019

Atmos. Chem. Phys.

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Abstract. The mechanisms of molecular halogen production from frozen saline surfaces remain incompletely understood, limiting our ability to predict atmospheric oxidation and composition in polar regions. In this laboratory study, condensed-phase hydroxyl radicals (OH) were photochemically generated in frozen saltwater solutions that mimicked the ionic composition of ocean water. These hydroxyl radicals were found to oxidize Cl−, Br−, and I−, leading to the release of Cl2, Br2, I2, and IBr. At moderately acidic pH (buffered between 4.5 and 4.8), irradiation of ice containing OH precursors (either of hydrogen peroxide or nitrite ion) produced elevated amounts of I2. Subsequent addition of O3 produced additional I2, as well as small amounts of Br2. At lower pH (1.7–2.2) and in the presence of an OH precursor, rapid dark conversion of I− to I2 occurred from reactions with hydrogen peroxide or nitrite, followed by substantial photochemical production of Br2 upon irradiation. Exposure to O3 under these low pH conditions also increased production of Br2 and I2; this likely results from direct O3 reactions with halides, as well as the production of gas-phase HOBr and HOI that subsequently diffuse to frozen solution to react with Br− and I−. Photochemical production of Cl2 was only observed when the irradiated sample was composed of high-purity NaCl and hydrogen peroxide (acting as the OH precursor) at pH = 1.8. Though condensed-phase OH was shown to produce Cl2 in this study, kinetics calculations suggest that heterogeneous recycling chemistry may be equally or more important for Cl2 production in the Arctic atmosphere. The condensed-phase OH-mediated halogen production mechanisms demonstrated here are consistent with those proposed from recent Arctic field observations of molecular halogen production from snowpacks. These reactions, even if slow, may be important for providing seed halogens to the Arctic atmosphere. Our results suggest the observed molecular halogen products are dependent on the relative concentrations of halides at the ice surface, as we only observe what diffuses to the air–surface interface.

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Section: Cimsmentioning

confidence: 99%

pH-dependent production of molecular chlorine, bromine, and iodine from frozen saline surfaces

Halfacre¹,

Shepson²,

Pratt³

2019

Atmos. Chem. Phys.

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“…However, the role of light is not straightforward, since I − absorbs below 250 nm, and light of this wavelength is not expected either in daylight or from our light source used for illumination. Based on previously reported data, we assume that I − interacts with O 2 in an oxygen‐saturated solution and forms the charge‐transfer complex (CTC) I − ⋅ O 2 , with a broad absorption at λ =310–360 nm, thus absorbing sunlight. Figure b shows a close‐up of the absorption spectrum recorded in the beginning of the experiment.…”

Section: Figurementioning

confidence: 99%

“…Importantly the process is light induced and does not take place in the dark, suggesting that photoexcitation of I À is the initial step. Oxygen is also crucial, since illuminated solution kept under N 2 does not show absorption changes.H owever, the role of light is not straightforward, since I À absorbs below 250 nm, and light of this wavelength is not expected either in daylighto rf rom our light source used for illumination.B ased on previously reported data, we assume that I À interacts with O 2 in an oxygen-saturated solution and forms the charge-transfer complex (CTC) I À ·O 2 ,w ith ab road absorption at l = 310-360 nm, [17,18] thus absorbing sunlight. Figure 2b shows ac loseup of the absorption spectrum recorded in the beginning of the experiment.…”

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confidence: 99%

Hindered Amine Light Stabilizers Increase the Stability of Methylammonium Lead Iodide Perovskite Against Light and Oxygen

et al. 2017

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Methylammonium lead iodide perovskite( MAPI) is ap romising materialf or highly efficient photovoltaic devices.H owever,i t suffers from photooxidation,whichimposes strict requirements for its protection from oxygen during processing and operation. Ah indered amine light stabilizer( HALS) has been found to exert as tabilization effect on methylammonium iodide (MAI) and MAPI against photooxidation. The HALS prevents the degradation of MAI by inhibiting the oxidation of iodide to iodine. Chemical modification of HALS allowsi ts incorporation in MAPI films, whiche xtendst he resistivity of MAPI against photodegradation in ambient air from ac ouple of hours to severald ays,w hile causing no significant changes in key properties, such as optical absorption and charge transport. These results represent an important advance in the stabilizationo f MAPI against decomposition and demonstrate for the first time that antioxidants improve the stability of MAPI.Methylammonium lead iodide perovskite (MAPI) solar cells constitute an emerging photovoltaict echnology that in recent years has shown an outstanding improvement in power conversion efficiency, surpassing 21 %.[1-6] However,d espite this significant progress, poor stabilityo fp erovskite devices remains am ajor issue. Factors such as light, oxygen, humidity, and temperature cause rapid degradation of perovskite solar cells (PSC). [7,8] This drawback hampers potential large-scale application of the devices, which must be able to operate for a sufficient length of time under real environmental conditions. Because PSC is ac omplexd evice, composed of MAPI absorber, charge extractionl ayers, and electrodes, multiple degradation phenomenao ccur in it. Most of the studies, relate the degradation of PSC with MAPI decomposition, yet degradation is also attributed to the role of the hole-transporting material, its additives,t he electron-extracting TiO 2 ,t he electrodes, or even the architecture of the device. [7][8][9][10] Recent studies have demonstrated that photooxidation (POX) of MAPI inducedb yl ight and oxygen is ad ominant factor limiting the lifetimeo fP SC under ambient conditions. [11] Photoexcited MAPI reacts with oxygen, resulting in the formation of superoxide anion,w hich in turn attacks the methylammoniumc ation thus initiating degradation of MAPI. Importantly,t he degradation rate may be reduced when effective electron extraction from the excited perovskite is ensured and the electron transfer from MAPI to oxygen is minimized. However, despite reduced photodegradationw hen TiO 2 is used as an electron acceptor,t he process cannot be completely suppressed, [12] since areas with poor electron extraction are present in ap olycrystalline MAPI layer.[13] These recent findings indicate unequivocally that MAPI is inherently unstable in the presence of oxygen andl ight. Furthermore,M API degradation in PSCs also occurs in the dark at forward bias when electrically injected electrons react with oxygen.[12] Photodegradation of one of the MAPI precursors, namely methyla...

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“…13 The instruments, apparatus and procedures for the quantitative analysis and for the physicochemical measurements have been described in detail [9][10][11]. Far-IR spectra were recorded as Nujol mulls supported between polyethylene sheets in a Perkin Elmer-Hitachi FIS-3 spectrophotometer, at room temperature.…”

Section: Analysis [%] For Hhgh • 2anmentioning

confidence: 99%

“…Its appearance indicates the existence of an equilibrium of the type HglJ Hgl2 + I -. The 350 nm, very broad maximum, which appears after a considerable lapse of time, is due to traces of the I3 ion [13]. There are two possible monomeric structures for the Hgl3~ ion, in the solid state.…”

mentioning

confidence: 98%

Compounds of Complex Halo and Pseudohalo Acids of the Group II B Metals, Part HI [1]Spectral Studies of the Hgl^- ₃ Ion

Perlepes

Zafiropoulos

Kouinis

et al. 1980

Zeitschrift Für Naturforschung B

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Spectrum and stability of oxygen iodide charge-transfer complex

Cited by 14 publications

References 6 publications

pH-dependent production of molecular chlorine, bromine, and iodine from frozen saline surfaces

pH-dependent production of molecular chlorine, bromine, and iodine from frozen saline surfaces

Hindered Amine Light Stabilizers Increase the Stability of Methylammonium Lead Iodide Perovskite Against Light and Oxygen

Compounds of Complex Halo and Pseudohalo Acids of the Group II B Metals, Part HI [1]Spectral Studies of the Hgl^- ₃ Ion

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Spectrum and stability of oxygen iodide charge-transfer complex

Cited by 14 publications

References 6 publications

pH-dependent production of molecular chlorine, bromine, and iodine from frozen saline surfaces

pH-dependent production of molecular chlorine, bromine, and iodine from frozen saline surfaces

Hindered Amine Light Stabilizers Increase the Stability of Methylammonium Lead Iodide Perovskite Against Light and Oxygen

Compounds of Complex Halo and Pseudohalo Acids of the Group II B Metals, Part HI [1]Spectral Studies of the Hgl- 3 Ion

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Compounds of Complex Halo and Pseudohalo Acids of the Group II B Metals, Part HI [1]Spectral Studies of the Hgl^- ₃ Ion