权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Elucidation of dissociation mechanisms of a dielectric barrier discharge for volatile species

阐明挥发性物质的介电阻挡放电的解离机制

基本信息

批准号：
290066525
负责人：
Privatdozent Dr. Joachim Franzke
金额：
--
依托单位：
Leibniz-Institut für Analytische Wissenschaften -ISAS- e.V.
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2016
资助国家：
德国
起止时间：
2015-12-31 至 2020-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/290066525?language=en
关键词：
Elucidation dissociation mechanisms dielectric barrier

项目摘要

In recent years, dielectric barrier discharges are frequently investigated and used for many purposes as, for instance, for ambient air ionization and soft ionization of organic molecules. Dielectric barrier discharges have also been investigated as alternative volatile species atomizers to replace the commonly used externally heated quartz tube atomizers in AAS as well as diffusion flames (DF) and flame-in-gas-shield (FIGS) atomizers in AFS. They have been proven as useful tools in analytical spectrometry since they may serve as a source of free atoms, excited species as well as ions. The main goal of this project is to develop a plasma capable of dissocia-tion/atomization of molecules and to elucidate dissociation mechanisms of a dielec-tric barrier discharge (DBD) for volatile species. In general, the properties of the plasmas generated by DBD strongly depend on electrode configuration and applied voltages. It is known from DBDs applied as soft ionization source that these discharges can be distinguished by different modes of operation, thus homogeneous and fila-mentary modes can exist. The DBD used for soft ionization should be operated in a homogeneous mode. Which mode of operation might be preferable when the DBD is applied as atomizer for volatile species? To answer this question, first of all a complete visual control of the plasma shape is necessary. Usually, the plasma is end-on observed in planar DBDs. However, no complete information about the operation mode of the plasma can be obtained in this manner. As a consequence, a planar shaped DBD with transparent Indium Tinn Oxide (ITO) electrodes of different geometries on glass will be applied in order not to see the plasma end-on only, but also to monitor the plasma emission characteristics along the electrodes through their surface. Different plasma designs will be applied for absorption and fluorescence measurements. Furthermore, discharge current measurements will be used to distinguish two different plasmas which will be temporally separated. The temporal first plasma might be the plasma which can be used for soft ionisation and the second the one which can be applied as dissociative plasma. In order to find out if the second plasma is the dissociative one a DB plasma-jet will be used because the distance of the electrodes is with 10 mm 4 to 5 times bigger than that of the distance in between the plates of the above constructed discharges. Therefore, temporal emission measurements in between the electrodes can be ob-tained and compared with the plasma currents. A plasma modulated lock-in detection will be developed in order to obtain an efficient detection with low detection limit (LOD). Modulated plasma measurements will be performed using Se hydride as model analyte and atomic absorption and fluorescence detectors. Additionally, a suppression of the background should be reached by intensity modulation of the hollow cathode lamp.

近年来，介质阻挡放电被频繁地研究并用于许多目的，例如用于环境空气电离和有机分子的软电离。介质阻挡放电也被研究作为替代挥发性物质雾化器，以取代常用的外部加热的石英管雾化器在原子吸收光谱法以及扩散火焰（DF）和火焰气体屏蔽（FIGS）雾化器在原子荧光光谱。它们被证明是分析光谱学中有用的工具，因为它们可以作为自由原子、激发态物质以及离子的来源。本项目的主要目标是研制一种能够离解/雾化分子的等离子体，并阐明介质阻挡放电（DBD）对挥发性物质的离解机理。一般来说，由DBD产生的等离子体的性质强烈地依赖于电极配置和施加的电压。从DBD作为软电离源的应用中可以看出，这些放电可以通过不同的操作模式来区分，因此可以存在均匀模式和丝状模式。用于软电离的介质阻挡放电应在均匀模式下工作。当介质阻挡放电用作挥发性物质的雾化器时，哪种操作模式可能是优选的？要回答这个问题，首先需要对等离子体形状进行完整的视觉控制。通常，在平面DBD中观察到的等离子体是端部的。然而，以这种方式不能获得关于等离子体的操作模式的完整信息。因此，将应用在玻璃上具有不同几何形状的透明铟锡氧化物（ITO）电极的平面形状的DBD，以便不仅看到等离子体端部，而且还通过电极的表面监测沿着电极的等离子体发射特性。不同的等离子体设计将应用于吸收和荧光测量。此外，放电电流的测量将被用来区分两个不同的等离子体，这将是暂时分开。时间上的第一等离子体可以是可用于软电离的等离子体，而第二等离子体可以是可用作离解等离子体的等离子体。为了确定第二等离子体是否是解离的等离子体，将使用DB等离子体射流，因为电极的距离为10 mm，比上述构造的放电的板之间的距离大4至5倍。因此，可以获得电极之间的时间发射测量，并与等离子体电流进行比较。将开发等离子体调制锁定检测，以获得低检测限（LOD）的有效检测。将使用Se氢化物作为模型分析物以及原子吸收和荧光检测器进行调制等离子体测量。另外，背景的抑制应当通过空心阴极灯的强度调制来实现。