ABSTRACT A sensitive, field-portable microplasma spectroscopy method has been developed for real-time measurement of carbon nanomaterials. The method involves microconcentration of aerosol on a microelectrode tip for subsequent analysis for atomic carbon using spark emission spectroscopy (SES). The spark-induced microplasma was characterized by measuring the excitation temperature (15,000–35,000 K), electron density (1.0 × 1017–2.2 × 1017 cm−3), and spectral responses as functions of time and interelectrode distance. The system was calibrated and detection limits were determined for total atomic carbon (TAC) using a carbon emission line at 247.856 nm (C I) for various carbonaceous materials including sucrose, EDTA, caffeine, sodium carbonate, carbon black, and carbon nanotubes. The limit of detection for total atomic carbon was 1.61 ng, equivalent to 238 ng m−3 when sampling at 1.5 L min−1 for 5 min. To improve the selectivity for carbon nanomaterials, which mainly consist of elemental carbon (EC), the cathode was heated to 300°C to reduce the contribution of organic carbon to the total atomic carbon. Measurements of carbon nanotube aerosol at elevated electrode temperature showed improved selectivity to elemental carbon and compared well with the measurements from the thermal optical method (NIOSH Method 5040). The study shows the SES method to be an excellent candidate for development of low-cost, hand-portable, real-time instrument for measurement of carbonaceous aerosols and nanomaterials.

中文翻译：

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使用微等离子体光谱法近实时测量碳气溶胶：在碳纳米材料测量中的应用


摘要：一种灵敏的、现场便携式微等离子体光谱方法已被开发用于碳纳米材料的实时测量。该方法涉及在微电极尖端上微量浓缩气溶胶，以便随后使用火花发射光谱 (SES) 进行原子碳分析。通过测量激发温度（15,000–35,000 K）、电子密度（1.0 × 1017–2.2 × 1017 cm−3）以及随时间和电极间距离变化的光谱响应来表征火花诱导的微等离子体。该系统经过校准，并使用 247.856 nm (CI) 的碳发射线确定了各种碳质材料（包括蔗糖、EDTA、咖啡因、碳酸钠、炭黑和碳纳米管）的总原子碳 (TAC) 检测限。总原子碳的检测限为 1.61 ng，相当于以 1.5 L min−1 采样 5 分钟时的 238 ng m−3。为了提高主要由元素碳（EC）组成的碳纳米材料的选择性，将阴极加热至300°C以减少有机碳对总原子碳的贡献。在升高的电极温度下对碳纳米管气溶胶的测量显示出对元素碳的选择性有所提高，并且与热光学方法（NIOSH 方法 5040）的测量结果进行了很好的比较。研究表明，SES 方法是开发用于测量碳质气​​溶胶和纳米材料的低成本、便携式实时仪器的绝佳候选方法。