Secondary Ozonide Formation from the Ozone Oxidation of Unsaturated Self-Assembled Monolayers on Zinc Selenide Attenuated Total Reflectance Crystals

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• 作者：Theresa M. McIntire ; Olivia Ryder ; Barbara J. Finlayson-Pitts
• 刊名：Journal of Physical Chemistry C
• 出版年：2009
• 出版时间：June 25, 2009
• 年：2009
• 卷：113
• 期：25
• 页码：11060-11065
• 全文大小：231K
• 年卷期：v.113,no.25(June 25, 2009)
• ISSN：1932-7455

文摘

The ozone oxidation of terminal unsaturated 7-octenyltrichlorosilane self-assembled monolayers (C8= SAMs) on ZnSe and on SiO_x-coated ZnSe was followed as a function of time using Fourier transform infrared spectroscopy (FTIR). Zinc selenide substrates have a major advantage over silicon crystals used in previous studies in that they transmit to approximately 650 cm⁻¹, well beyond the cutoff of 1500 cm⁻¹ for silicon ATR crystals, and thus allow detection of additional product species. When uncoated ZnSe or SiO_x-coated ZnSe ATR crystals with a C8= SAM are exposed to gaseous ozone at concentrations from 10¹³ to 10¹⁵ molecules cm⁻³ at 1 atm pressure in He at 296 K, peaks due to C═CH decrease and a strong product peak at 1110 cm⁻¹ as well as a weaker peak at 1385 cm⁻¹ increase, both of which are attributed to the formation of a stable secondary ozonide (1,2,4-trioxolane, SOZ). Peaks at 2860 and 2929 cm⁻¹ are also formed, which we tentatively assign to the C−H stretch of the OC−H group in the SOZ. The magnitude of the 1110 cm⁻¹ band relative to those due to carbonyl groups at 1722 cm⁻¹ suggests that SOZ may, in fact, be the major reaction product. The SOZ has a sufficiently long lifetime when formed in the condensed phase that it is stabilized on the surface, indicating secondary ozonides may be formed during organic oxidations on surfaces in the atmosphere.