Electrospray surface-enhanced Raman spectroscopy (ES-SERS) for studying organic coatings of atmospheric aerosol particles
Electrospray surface-enhanced Raman spectroscopy (ES-SERS) for studying organic coatings of atmospheric aerosol particles
复制标题
用于研究大气气溶胶颗粒有机涂层的电喷雾表面增强拉曼光谱 (ES-SERS)
DOI：
10.1080/02786826.2019.1597964
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发表时间：
2019-04-07
影响因子：
5.2
通讯作者：
Chan, Chak K.
中科院分区：
文献类型：
--
作者：
Gen, Masao;Kunihisa, Ryota;Chan, Chak K.
大气气溶胶颗粒与气态污染物之间的非均相反应是一种重要的机理。这些反应改变了颗粒的化学成分和气溶胶与气候的相互作用。虽然大多数研究假设颗粒组成均匀，但由于多相反应，可以在固体或高粘性颗粒上形成有机涂层，但其潜在机制相对较少被研究。我们使用电喷雾表面增强拉曼光谱(ES-SERS)直接探测了气相乙二醛与甲基铵、硝酸盐和氯化物颗粒的多相反应形成BRC涂层的过程。为了在颗粒表面形成BRC涂层，在低相对湿度(RH)条件下(即，RH为10%或30%)进行了多相反应。在正常的拉曼分析中，反应粒子在532 nm处发光，间接表明其中存在光吸收物种。进一步的ES-SERS分析表明，乙二醛与甲胺反应的主要已知产物1，3-二甲基咪唑在30%相对湿度下的所有反应颗粒中都有拉曼谱带。然而，在相对湿度为10%时，只有甲基硫酸铵颗粒显示出BRC涂层的形成。我们推测，硫酸甲铵颗粒可能比其他颗粒样品具有更多的表面吸附水(SAW)，从而启动了ES-SERS可检测到的BRC涂层的形成。本研究强调了表面增强拉曼光谱的表面敏感性，以及表面波在大气颗粒物与气态污染物多相反应中的潜在重要性。版权所有(C)2019美国气溶胶研究协会
Abstract Heterogeneous reactions between atmospheric aerosol particles and gaseous pollutants, such as those forming brown carbon (BrC), represent an important mechanism. These reactions alter the particle chemical compositions and aerosol-climate interactions. While most studies assume homogeneous particle compositions, organic coatings can be formed on solid or highly viscous particles due to heterogeneous reactions but the underlying mechanism is relatively less examined. We used electrospray surface-enhanced Raman spectroscopy (ES-SERS) to directly probe the formation of BrC coatings on methylaminium sulfate, nitrate, and chloride particles from heterogeneous reactions with gas-phase glyoxal. To create BrC coatings on particle surfaces, heterogeneous reactions were performed under low relative humidity (RH) conditions (i.e., 10 or 30% RH). The reacted particles fluoresced when irradiated at 532 nm in normal Raman analysis, indirectly suggesting the presence of light-absorbing species in them. Further ES-SERS analyses showed Raman bands of 1,3-dimethylimidazole, one of the major known products of reactions of glyoxal with methylaminium, from all the reacted particles at 30% RH. However, only methylaminium sulfate particles showed the formation of BrC coatings at 10% RH. We speculate that methylaminium sulfate particles may have more surface adsorbed water (SAW) than the other particle samples to initiate the formation of BrC coatings detectable by ES-SERS. The present study highlights the surface sensitivity of ES-SERS as well as the potential importance of SAW in heterogeneous reactions of atmospheric particles with gaseous pollutants. Copyright © 2019 American Association for Aerosol Research