Kinetically controlled glass transition measurement of organic aerosol thin films using broadband dielectric spectroscopy
Kinetically controlled glass transition measurement of organic aerosol thin films using broadband dielectric spectroscopy
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DOI：
10.5194/amt-11-3479-2018
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发表时间：
2018-06
影响因子：
3.8
通讯作者：
Yue Zhang;Shachi Katira;Andrew L. Lee;A. Lambe;T. Onasch;Wen Xu;W. Brooks;M. Canagaratna;A. Freedman;J. Jayne;D. Worsnop;P. Davidovits;D. Chandler;C. Kolb
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文献类型：
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作者：
Yue Zhang;Shachi Katira;Andrew L. Lee;A. Lambe;T. Onasch;Wen Xu;W. Brooks;M. Canagaratna;A. Freedman;J. Jayne;D. Worsnop;P. Davidovits;D. Chandler;C. Kolb
抽象的。从液态到半固态和固态的玻璃化转变对二次有机气溶胶的反应性、生长和云形成(云凝结核和冰核)能力具有重要影响。由于大气中SOAs的体积较小，质量浓度相对较低，因此很难用常规方法测量大气中SOAs的玻璃化转变。为了绕过这些困难，我们采用了一种新的技术来测量与大气相关的有机气溶胶的玻璃形成特性。利用静电沉淀法将待研究的气溶胶粒子以薄膜的形式沉积到交错指电极(IDE)上。介电光谱学提供有机气溶胶的偶极弛豫率作为温度(373至233K)的函数，用于计算几种冷却或加热速率下的玻璃化转变温度。利用IDE使能宽带介电谱(BDS)成功地测量了由甘油和其他四种化合物组成的气溶胶在选定的冷却和升温速率下的动力学控制玻璃化转变温度。这五种化合物的玻璃化转变结果与已有的文献数据符合得很好。结果表明，IDE-BDS方法可以提供大气条件下有机气溶胶的玻璃化转变数据。利用IDE-BDS技术获得的BDS数据可用于描述模拟和环境有机气溶胶的玻璃化转变，并对其气候影响进行模拟。
Abstract. Glass transitions from liquid to semi-solid and solid phase states have important implications for reactivity, growth, and cloud-forming (cloud condensation nuclei and ice nucleation) capabilities of secondary organic aerosols (SOAs). The small size and relatively low mass concentration of SOAs in the atmosphere make it difficult to measure atmospheric SOA glass transitions using conventional methods. To circumvent these difficulties, we have adapted a new technique for measuring glass-forming properties of atmospherically relevant organic aerosols. Aerosol particles to be studied are deposited in the form of a thin film onto an interdigitated electrode (IDE) using electrostatic precipitation. Dielectric spectroscopy provides dipole relaxation rates for organic aerosols as a function of temperature (373 to 233 K) that are used to calculate the glass transition temperatures for several cooling or heating rates. IDE-enabled broadband dielectric spectroscopy (BDS) was successfully used to measure the kinetically controlled glass transition temperatures of aerosols consisting of glycerol and four other compounds with selected cooling and heating rates. The glass transition results agree well with available literature data for these five compounds. The results indicate that the IDE-BDS method can provide accurate glass transition data for organic aerosols under atmospheric conditions. The BDS data obtained with the IDE-BDS technique can be used to characterize glass transitions for both simulated and ambient organic aerosols and to model their climate effects.