Liquid-Liquid Phase Separation in Aerosol Particles: Imaging at the Nanometer Scale

被引：80

作者：

O'Brien, Rachel E. ^{[1
]}

Wang, Bingbing ^{[2
]}

Kelly, Stephen T. ^{[1
]}

Lundt, Nils ^{[1
,3
]}

You, Yuan ^{[5
]}

Bertram, Allan K. ^{[5
]}

Leone, Stephen R. ^{[1
,3
,4
]}

Laskin, Alexander ^{[2
]}

Gilles, Mary K. ^{[1
]}

机构：

[1] Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Div Chem Sci, Berkeley, CA 94720 USA

[2] Pacific NW Natl Lab, William R Wiley Environm & Mol Sci Lab, Richland, WA 99352 USA

[3] Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA

[4] Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA

[5] Univ British Columbia, Dept Chem, Vancouver, BC V6T 1Z1, Canada

来源：

ENVIRONMENTAL SCIENCE & TECHNOLOGY | 2015年 / 49卷 / 08期

关键词：

AMMONIUM-SULFATE; ELECTRON-MICROSCOPY; INORGANIC SALTS; ORGANIC AEROSOL; REACTIVE UPTAKE; ACID PARTICLES; MORPHOLOGY; DELIQUESCENCE; COMPONENT; DROPLETS;

D O I：

10.1021/acs.est.5b00062

中图分类号：

X [环境科学、安全科学];

学科分类号：

08 ; 0830 ;

摘要：

Atmospheric aerosols can undergo phase transitions including liquid liquid phase separation (LLPS) while responding to changes in the ambient relative humidity (RH). Here, we report results of chemical imaging experiments using environmental scanning electron microscopy (ESEM) and scanning transmission X-ray microscopy (STXM) to investigate the LLPS of micrometer-sized particles undergoing a full hydration-dehydration cycle. Internally mixed particles composed of ammonium sulfate (AS) and either: limonene secondary organic carbon (LSOC), alpha, 4-dihydroxy-3-methoxybenzeneaceticacid (HMMA), or polyethylene glycol (PEG-400) were studied. Events of LLPS were observed for all samples with both techniques. Chemical imaging with STXM showed that both LSOC/AS and HMMA/AS particles were never homogeneously mixed for all measured RH's above the deliquescence point and that the majority of the organic component was located in the outer phase. The outer phase composition was estimated as 65:35 organic: inorganic in LSOC/AS and as 50:50 organic: inorganic for HMMA/AS. PEG-400/AS particles showed fully homogeneous mixtures at high RH and phase separated below 89-92% RH with an estimated 70:30% organic to inorganic mix in the outer phase. These two chemical imaging techniques are well suited for in situ analysis of the hygroscopic behavior, phase separation, and surface composition of collected ambient aerosol particles.

引用

页码：4995 / 5002

页数：8

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