Abstract A review of methodologies to measure the bipolar charge distribution of nanoparticles is completed, including their advantages/disadvantages and sequential development. This summary also provides context for a new development, which uses an Aerodynamic Aerosol Classifier (AAC) and Differential Mobility Analyzer (DMA) in tandem for a similar purpose. It is demonstrated that the tandem AAC-DMA system overcomes some significant limitations of the previous methodologies, such as multiply-charged particle artefacts and low measurement signals. The tandem AAC-DMA methodology also has the sensitivity to detect other charging phenomena, such as the effects of different sample flow rates through the charger, free-ions downstream of the charger, the inlet insert on the 85Kr charger and different particle chargers (x-ray, old 85Kr and new 85Kr). The charge fractions of the particles at low-flow (0.6 L/min) through the new 85Kr charger agreed well (average absolute difference of 0.007) with widely-used charging theory. However, significant deviations from theory (up to a 0.044 difference in charge fractions) were found with a higher sample flow rate (1.2 L/min), with different exposure times to free-ions downstream of the charger, or with the inlet insert on the new 85Kr charger. It was found that regardless of flow rate, a soft x-ray charger resulted in charge fractions which deviated significantly from theory (up to a 0.084 difference in charge fractions), producing higher fractions of positively charged particles and lower fractions of negatively charged particles relative to theory. All of these deviations are likely due to the simplifying assumptions made by the charging theory. Therefore, rigorous measurement of particle charge distributions are necessary for accurate aerosol characterization, such as standard SMPS measurements.

中文翻译：

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测量纳米粒子的双极电荷分布：使用气动气溶胶分类器的方法和开发回顾

摘要 完成了测量纳米颗粒双极电荷分布的方法的综述，包括它们的优缺点和顺序发展。本摘要还为一项新开发提供了背景信息，该开发将空气动力学气溶胶分类器 (AAC) 和差分迁移率分析仪 (DMA) 串联使用以达到类似目的。结果表明，串联 AAC-DMA 系统克服了先前方法的一些重大局限性，例如多电荷粒子伪影和低测量信号。串联 AAC-DMA 方法还具有检测其他充电现象的灵敏度，例如通过充电器的不同样品流速、充电器下游的自由离子、85Kr 充电器上的入口插件和不同粒子充电器 (x -ray、旧的 85Kr 和新的 85Kr）。通过新型 85Kr 充电器的低流量 (0.6 L/min) 颗粒的电荷分数与广泛使用的充电理论非常吻合（平均绝对差为 0.007）。然而，在较高的样品流速 (1.2 L/min)、充电器下游的自由离子暴露时间不同或入口插入件打开时，发现与理论的显着偏差（电荷分数差异高达 0.044）新的 85Kr 充电器。发现无论流速如何，软 X 射线充电器都会导致电荷分数与理论显着偏离（电荷分数差异高达 0.084），产生较高分数的带正电粒子和较低分数的带负电粒子相对到理论。所有这些偏差都可能是由于充电理论所做的简化假设。