芳香醛在微液滴中的自发氧化和水合及其在大气中的潜在意义  

Spontaneous Oxidation and Hydration of Aromatic Aldehydes in Microdroplets and its Atmospheric Implications

作　　者：梁驰予 张新星 LIANG Chi-yu;ZHANG Xin-xing(College of Chemistry,Nankai University,Tianjin 300071,China)

机构地区：[1]南开大学化学学院,天津300071

出　　处：《质谱学报》2023年第2期242-250,共9页Journal of Chinese Mass Spectrometry Society

基　　金：天津市大学生创新创业训练计划(202210055372);国家自然科学基金(22174073,22003027);天津市杰出青年基金(21JCJQJC00010);北京分子科学国家研究中心开放基金(BNLMS202106)。

摘　　要：微液滴具有许多独特的性质,基于其庞大的表面以及极高的表面电场,能够加速反应的发生或引发体相中无法进行的反应。大气气溶胶的尺寸与微液滴相近,可以使用微液滴装置模拟大气气溶胶气液界面发生的重要大气化学过程。醛类物质是二次有机气溶胶(SOA)的重要来源,研究其水合与氧化过程有助于理解挥发性有机物(VOCs)向SOA的转化。本工作使用气动喷雾法生成微液滴,考察几种芳香醛在微液滴中的行为,并直接引入质谱进行在线表征。结果表明,芳香醛能够在微液滴中自发氧化生成羧酸,并被该羧酸根诱导水合,形成不稳定的“羧酸根-水合醛”复合离子。这些复合离子是大气醛氧化反应的潜在中间体,其产生与微液滴的极端酸碱环境和丰富的活性氧物种含量密切相关。Microdroplets have many unique features derived from the large surface-volume ratio and the ultrahigh electric field at the air-water interface,therefore they can remarkably accelerate various slow reactions and trigger reactions that won’t occur in bulk solutions.The size of atmospheric aerosols is similar to that of the microdroplets,so reactions performed in microdroplets and ambient conditions can act as good simulations of important atmospheric processes,which will provide a better understanding of the role of aerosols.Aldehydes are important oxidized species in the atmosphere derived from releases of human activities,such as vehicle emissions and biomass burning,which can generate volatile organic compounds(VOCs)and are highly related to salt-rich aerosol formation through further oxidation.Studying of aldehydes’hydration and oxidation reactions is very helpful for understanding the complex conversion process from VOCs to secondary organic aerosols(SOA).In this work,several aromatic aldehydes with different electron donating or withdrawing groups were studied by spraying their solutions into microdroplets,then directly characterizing them by online mass spectrometry.It showed that these aromatic aldehydes could be oxidized into carboxylic acids under the space-restricting condition of microdroplets,and the hydration reactions of aromatic aldehydes could be induced by carboxylate under the extreme pH environment and abundant reactive oxygen species provided by the air-water interface of microdroplets.Together,the products of oxidation and hydration reactions would combine to yield relatively unstable“carboxylate-aldehyde hydrate”complex ions.The lifetime of the ions was roughly estimated by conducting a collision-induced disassociation(CID)experiment and comparing it to the instrument running procedure,and the structure was checked using CID and a cross-forming reaction between two different aldehydes.This work revealed that the complex ions were potential intermediates of the atmospheric aldehyde ox

关 键 词：微液滴 醛水合物 质谱 挥发性有机物(VOCs) 二次有机气溶胶(SOA) 

分 类 号：O657.63[理学—分析化学]