DRIFTS Studies on the Role of Surface Water in Stabilizing Catechol鈥揑ron(III) Complexes at the Gas/Solid Interface
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- 作者：Julia Tofan-Lazar ; Arthur Situm ; Hind A. Al-Abadleh
- 刊名：Journal of Physical Chemistry A
- 出版年：2013
- 出版时间：October 10, 2013
- 年：2013
- 卷：117
- 期：40
- 页码：10368-10380
- 全文大小：599K
- 年卷期：v.117,no.40(October 10, 2013)
- ISSN：1520-5215
文摘
Surface water plays a crucial role in facilitating or inhibiting surface reactions in atmospheric aerosols. However, little is known about the role of surface water in the complexation of organic acid molecules to transition metals in multicomponent aerosol systems. We report herein results from real time DRIFTS experiments that show in situ complexation of catechol to Fe(III) under humid conditions. Catechol was schosen as a simple model for humic-like substances (HULIS) in aerosols and aged polyaromatic hydrocarbons (PAH). It was also detected in secondary organic aerosols (SOA) formed from the reaction of hydroxyl radicals with benzene. Given the importance of the iron content in aerosols and its biogeochemistry, our studies were conducted using FeCl3. For comparison, these surface-sensitive studies were complemented with bulk aqueous ATR-FTIR, UV鈥搗is, and HPLC measurements for structural, quantitative, and qualitative information about complexes in the bulk, and potential degradation products in the dark. Under dry conditions, DRIFTS spectra show that gas phase catechol adsorbs molecularly and is fully protonated on samples containing FeCl3 with no evidence of complexation to Fe(III). Upon increasing the relative humidity to a value below the deliquescence of FeCl3, surface water facilitates ionic mobility resulting in the formation of monodentate catechol鈥揊e complexes. These complexes are stable at the gas/solid interface and do not undergo any further degradation in the dark as shown from bulk UV鈥搗is and HPLC experiments. The implications of our studies on understanding interfacial and condensed phase chemistry relevant to multicomponent aerosols, water thin films on buildings, and ocean surfaces containing transition metals are discussed.