ABSTRACT Measuring aerosols and molecular clusters below the 3 nm size limit is essential to increase our understanding of new particle formation. Instruments for the detection of sub-3 nm aerosols and clusters exist and need to be carefully calibrated and characterized. So far calibrations and laboratory tests have been carried out using mainly electrically charged aerosols, as they are easier to handle experimentally. However, the charging state of the cluster is an important variable to take into account. Furthermore, instrument characterization performed with charged aerosols could be biased, preventing a correct interpretation of data when electrically neutral sub-3 nm aerosols are involved. This article presents the first steps to generate electrically neutral molecular clusters as standards for calibration. We show two methods: One based on the neutralization of well-known molecular clusters (mobility standards) by ions generated in a switchable aerosol neutralizer. The second is based on the controlled neutralization of mobility standards with mobility standards of opposite polarity in a recombination cell. We highlight the challenges of these two techniques and, where possible, point out solutions. In addition, we give an outlook on the next steps toward generating well-defined neutral molecular clusters with a known chemical composition and concentration. Published with license by American Association for Aerosol Research

中文翻译：

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通过受控中和迁移率标准来生产中性分子簇

摘要 测量小于 3 nm 尺寸限制的气溶胶和分子簇对于增加我们对新粒子形成的理解至关重要。存在用于检测亚 3 纳米气溶胶和团簇的仪器，需要仔细校准和表征。到目前为止，校准和实验室测试主要是使用带电的气溶胶进行的，因为它们在实验上更容易处理。然而，集群的充电状态是一个需要考虑的重要变量。此外，使用带电气溶胶进行的仪器表征可能存在偏差，当涉及电中性亚 3 nm 气溶胶时，会妨碍对数据的正确解释。本文介绍了生成电中性分子簇作为校准标准的第一步。我们展示了两种方法：一种基于通过可切换气溶胶中和器中产生的离子中和众所周知的分子簇（迁移率标准）。第二种是基于在重组细胞中具有相反极性的迁移率标准的迁移率标准的受控中和。我们强调这两种技术的挑战，并在可能的情况下指出解决方案。此外，我们展望了生成具有已知化学成分和浓度的明确中性分子簇的下一步。经美国气溶胶研究协会许可出版 第二种是基于在重组细胞中具有相反极性的迁移率标准的迁移率标准的受控中和。我们强调这两种技术的挑战，并在可能的情况下指出解决方案。此外，我们展望了生成具有已知化学成分和浓度的明确中性分子簇的下一步。经美国气溶胶研究协会许可出版 第二种是基于在重组细胞中具有相反极性的迁移率标准的迁移率标准的受控中和。我们强调这两种技术的挑战，并在可能的情况下指出解决方案。此外，我们展望了生成具有已知化学成分和浓度的明确中性分子簇的下一步。经美国气溶胶研究协会许可出版