【作者】 李宇；

【导师】 麻远；

【作者基本信息】 清华大学 ， 化学， 2016， 硕士

【摘要】 气态负离子能够有效去除雾霾、降解有害污染气体和改善人体健康,具有广阔的应用前景,但对气态负离子中起关键作用的离子目前还不清楚,这需要对产生的气态负离子有着实时检测分析的技术。质谱由于具有特异性强、灵敏度高和实时检测鉴定的优势,能够通过特征质荷比峰来对气态负离子的成分进行鉴定,成为气态负离子有力的分析工具。本论文使用敞开式质谱对气态负离子进行研究,内容如下:1.搭建了基于T型玻璃管进样的气态负离子质谱检测装置,提供了一个便捷的平台用于不同气氛下产生气态负离子的实时在线质谱分析。实验研究了在高纯氧气、合成空气、高纯氮气和氩气气氛下基于电晕放电法产生的气态负离子的种类,并对气态负离子进行二级质谱检测以实现对这些离子的进一步鉴定。由于电晕放电过程受外界环境影响因素较大,我们还研究了针尖端电压和气体流速对产生的气态负离子种类及强度的影响。通过实现对这些气态负离子的检测,理解气态负离子的产生机理,有助于产生特定种类的气体负离子,可以使用产生的特定气态负离子进行后续的实验分析。2.研究了空气负离子的形成过程及其对室内有机污染物比如醛类、苯同系物类和酯类的降解行为。在T型玻璃管中通入合成空气(21%氧气+79%氮气)进行电晕放电能够优化产生出单一的空气负离子CO3-,该方法具有良好的稳定性、可重现性和高强度。通过将该空气负离子与室内污染物液体喷雾在线交叉混合并导入质谱进行实时监测提供了一个便利的平台来研究空气负离子的化学反应性质。相应的中间产物能够在二者反应的过程中被检测出来,这将帮助我们归纳空气负离子对不同种类化合物的反应规律。实验结果证实了空气负离子能够被用于醛类、苯同系物类和酯类化合物的消除。该方法能扩展用于常规电喷雾质谱难以检测的物质的电离或用于气态离子和其它化合物相互作用的研究。综上所述,本研究论文提出了气态负离子质谱分析的新方法,实现了对不同气氛下电晕放电产生气态负离子以及气态负离子与有机化合物相互作用的实时在线质谱分析,在气态负离子的基础和应用研究中都有着重要的意义。更多还原

【Abstract】 Gaseous negative ions can effectively remove haze,degrade indoor organic pollutants and improve human health,which has a broad application prospect.However,the gaseous negative ions which play an important role in the process have been unknown to us.A near-real-time detection method is sought for the analysis of gaseous negative ions.Mass spectrometry,with high specificity,sensitivity and online detection,becomes a powerful tool for the identification of gaseous negative ions according to the obtained mass to charge ratio.In this thesis,an ambient mass spectrometry is applied to this research.The contents were summarized as follows:1.We established a tube flow based atmospheric pressure corona discharge mass spectrometry system,providing a convenient platform for a near-real-time detection of gaseous negative ions generated in specific gas.Ions species produced in oxygen,synthetic air,nitrogen and argon atmosphere were investigated,and secondary mass spectrometry detection was utilized for further identification of these ions.Allowing for the sensibility of corona discharge within various external environments,vital factors including the tip voltage and gas flow rate were investigated to assess their influences on the generation of gaseous negative ions.It contributed to understanding of formation mechanism in corona discharge based on the detected ions.Besides,the produced negative ions could be used for subsequent experiments.2.The evolution of negative air ions and relevant degrading performance on indoor organic contaminants like aldehydes,benzene homologues and esters were investigated in this work.Negative air ions composed of a single ion species CO3-could be produced in T-shaped tube with atmosphere pressure corona discharge ionization in synthetic air(21% O2+79% N2),which displayed excellent stability,reproducibility and intensity.Combining gaseous ions with IOCs spray provided a convenient platform for study of chemical properties of negative air ions and interactions with IOCs.Relevant intermediate products could be detected during combination process,which helped us to conclude principles according to different reactants.Besides,negative air ions could be applied to the tentative clearance of aldehydes,benzene homologues and esters.It was also believed that this strategy could be extended to the ionization of substance which was difficult for traditional ESI source.This platform proved to be an efficient method for analysis of the interactions between specific negative ions and various chemical compounds.In conclusion,we have successfully developed several novel methods for analysis of gaseous negative ions through mass spectrometry.These innovative ideas have been applied to a near-real-time detection of gaseous negative ions generated in specific gas and their interactions with organic compounds through mass spectrometry.We believe that our developed platform will be of great significance in the basic and applied research in gaseous negative ions.更多还原